The Traditional Roofing Network ... Historic Preservation in Action

 Email Article  

  

  

 delicious  

  

The Traditional Roofing Network, a new organization that brings contractors, material suppliers, consultants, and preservationists together, launched its new website, TraditionalRoofing.net, this past weekend.  The cardinal tenet of the association is a belief that the use of traditional materials is at the core of sustainable design in historic preservation.

From slate roofing to thatch, to cedar and cyprus wood shingles, to clay tile and copper sheet metal, the preservation trades are well represented by material suppliers and craftsmen listings.  With new members joining daily, the site will continue to grow into an invaluable directory for finding services and vendors.

An integral part of the new site are the educational resources offered.  Ask the Experts is a free forum where specialists in the field can provide no nonsense answers to difficult questions about traditional roofing and appropriate preservation practices.  There are also videos, links to associated organizations, info on historic tax credits, and technical preservation briefs to provide further guidance and direction.

Click here and check us out today at TraditionalRoofing.Net ... The Traditional Roofing Network ... At the core of sustainable design in historic preservation.

Preservation consultation and documentation services

 Email Article  

  

  

 delicious  

  

Back to school: Slate Roofing 101

 Email Article  

  

  

 delicious  

  

Slate has been used as a roofing material for centuries in Europe.  It has been the preferred choice for homes and buildings in the northeastern United States since the late nineteenth century.  Slate roofs are still seen, frequently, in upstate New York, where tremendous building and growth took place in the early twentieth century during slate’s boom.  Schenectady, for example, grew from a population of 13,500 in 1880 to 32,000 in 1900.  Twenty years later, it was 89,000.  The slate quarries of Granville, New York, and Vermont lay a mere 60 miles to the north.  Many of the original slate roofs from this period survive today.

What does not exist, however, is a ready-supply of competent, capable contractors to repair and restore slate roofs.  With a basic understanding of this highly-specialized roofing system, home owners can generally assess the current condition of their slate roof, its life expectancy and, if necessary, the potential for restoration.  The information that follows will help in assessing and identifying your roof’s needs as you, armed with this information, carefully screen potential roofing contractors to effect these repairs.  Olde Mohawk Masonry & Historic Restoration is the preferred contractor for such work in New York and New England.

What goes wrong with slate roofs?

In most instances, the problem is one of the following:

• Variations in duration and quality

• Flashings and other metalwork need replacement

• Earlier repairs by irresponsible roofing contractors 

Variations in duration and quality of slate

Slate is pulled from the earth in massive slabs and dressed down into individual shingles mostly by hand.  Slate is stone, and stone is long lasting. However, stone is a natural material and may have minute or even invisible fissures that will ultimately cause slates to break and slide off the roof.  Roofing slates are rated by ANSI according to hardness.  Softer slates (rated S2 or S3) may become crumbly and will delaminate, sometimes, as early as 55 years, and certainly by 80-100 years.  These softer slate roofs (commonly from Pennsylvania) cannot be saved or restored, for the most part, but repairs can buy time.  

Good, hard slates, like most New York, Vermont, Peach Bottom, Buckingham, or Monson slates, will last for hundreds of years on a properly cared for roof.  It is critical that people who own, inspect or work on slate roofs are able to identify the slate on the roof in question.  This single-most important information will provide details as to its type, origin, longevity, characteristics, and qualities.  Contact Olde Mohawk for a free consultation specific to your slate roof.  Roofing slate is still being quarried and sold in New York and Vermont (as well as Pennsylvania and Virginia.)   Slate was also once quarried in Georgia and Maine (home of the world-famous Monson slate.)

Flashing replacement and built-in gutters

While the slate may last “forever,” the metal flashings will not.  Flashings are essentially the metalwork used to prevent the penetration of water wherever there is an abrupt angle or opening in the roof (ie, chimneys, valleys, dormers.)  Often, flashings were made from terne-coated steel, which is a steel coated with a lead/tin combination.  This is sometimes, incorrectly, called “tin.”  Terne-coated steel has to be painted regularly or corrosion will occur.  

Copper flashings (either plain copper or lead-coated) were most commonly installed  on government buildings, churches, and similar institutions and upscale homes.  Copper will oxidize as vert de gris appears.  Copper will begin to fail after about 60 to 70 years in areas of high wear, such as valleys.  The copper industry suggests a life of 80 years.  Older copper flashings can be painted in order to extend their lives.  Too often, the flashings fail and unscrupulous roofing contractors convince homeowners to replace their good, slate roof with asphalt.  Only the flashings should be replaced, not the entire roof.

These types of projects are routine for slate roof restoration contractors.  The adjoining slates are removed to allow for replacement of the flashings.  The removed slate are then installed in their original locations, laving the roof, in appearance, as it was before, except for the flashing.  The standard upon which a repair is judged is that it must not appear to the layperson that any repair, at all, took place, except for new, visible flashings.

Box gutter linings, or “built-in” gutters, are another common problem on old slate roofs because the metal deteriorates and leaks. Just like valleys and other flashings, they can be replaced without removing and replacing the entire roof.  If left unchecked, the entire gutter boxes will rot and need to be rebuilt and replaced.

Beware of irresponsible roofing contractors

The cause of many leaking slate roofs is not natural wear, metal failures, or even cracked slates.  It is, quite simply, bad work.  Many unqualified people claim to have the ability to repair slate roofs.  Fully half of the work done annually by a typical slate roofing contractor involves the removal and replacement of faulty repair work.  Home owners with slate roofs often pay exorbitant sums to have their roofs trashed by these fly-by-nighters, then they have to pay even more of their hard-earned money to have them fixed and repaired correctly.  The types abuses committed against slate roofs include the ones that are face-nailed, tarred, repaired with non-matching slates, coated, or reflashed incorrectly (see photos below).  One should NEVER tar or coat the surfaces of slate roofs.  Such actions are aesthetically displeasing, often irreversible, and ineffective.  Roofing contractors are notorious for advising homeowners to replace a perfectly good roof.  Home owners will often listen to such advice when a lack of competent slaters makes it the only advice available.  These issues, combined, have been the downfall of countless slate roofs, lost forever to ignorance, neglect, and despair. Contact Olde Mohawk for a free assessment and discussion of your roof’s needs.  As you seek estimates and advice from other roofers, use the information in this document to test their knowledge and screen their methods.  Watch their eyes widen as they realize YOU know more about slate roofing than they do! 

Replacing broken and missing slate

It is not uncommon for a century-old slate roof to have 50 or more slates simply fail from a variety of causes.  Slate contains natural faults or hairline cracks and may eventually break.  A 20 square roof (2,000 square feet), with a typical 10"x 20" slate, will have about 3,400 slates.  If 50 of them fail after a hundred years, then the failure rate of the roof is 1.5 percent over 100 years— or a 98.5 percent success rate over a century.   That’s an A+.   However, just one missing slate is all a leak needs to get started.  For a professional slater, the solution is not rocket science.  Replacement slates must never be fastened in place with visible straps or exposed nails (known as “face-nails”).  I repeat, if a roofer describes face-nailing to you as his preferred method, tell him to leave your property IMMEDIATELY. NEVER let him on your roof and ask him to forget your address.  Ask that he not even look at the slate if he ever happens to drive past your house in the future!

There are two acceptable techniques for fastening replacement slates:  the “nail and bib” method or the “slate hook”.  The nail and bib method is the most widely used. The broken slate is removed with a slate ripper and the replacement slate is anchored with a nail in the slot between the two, overlying slates.  A small square of flashing is slid under the two, overlying slates on the next course, above, and over the new nail head.  The bib is bent a little so friction keeps it in place.  Bibs can be aluminum, copper, or other non-corrodible metal, but shiny and reflective metals that are visible from the ground should never be used. 

Copper or brown-painted aluminum (coilstock) blends nicely into the roof.  A slate hook is a hard wire hook made of galvanized steel, copper or stainless steel, approximately three inches long.  A small exposed loop hooks the replacement slate in place. This is one instance when an exposed repair device is acceptable because the tiny hook is almost invisible from the ground.  Stainless steel hooks are stronger than copper hooks.  Slate hooks are preferable to the nail and bib on new slate roofs, especially for repairs in the field of the roof.  Using straphangers to repair the roof should be avoided; they’re unsightly and they deface the roof.

The tool required for removing slates from a roof is the slate ripper—a swordlike object that slides up under the slate and yanks out the two nails that hold it in place.  You never want to cut the nail because the piece of nail left under the slate will interfere with sliding the replacement slate into place.  A slate hammer, another important slate roofing tool, has a hole punch at one end used to punch nail holes in slates.  New slates can be hard and brittle and require some practice for easy punching with a slate hammer.  Standard thickness slates (3/16" to 1/4") are readily cut with a simple hand-held device, a slate cutter.

Conclusion

While the slate roof may last “forever,” the metal flashings will not.  Not all slate is the same in quality and durability. Unscrupulous roofers will butcher your roof or even replace it with asphalt shingles, if you let them.  Armed with the above information, you are ready to question potential slaters and assess your roof’s needs.  Please contact Olde Mohawk so that we may assist you.

Tax Incentives for Preserving Historic Properties

 Email Article  

  

  

 delicious  

  

The Federal Historic Preservation Tax Incentives program encourages private sector investment in the rehabilitation and re-use of historic buildings. It creates jobs and is one of the nation's most successful and cost-effective community revitalization programs. It has leveraged over $58 billion in private investment to preserve 37,000 historic properties since 1976. The National Park Service and the Internal Revenue Service administer the program in partnership with State Historic Preservation Offices.

20% Tax Credit

A 20% income tax credit is available for the rehabilitation of historic, income-producing buildings that are determined by the Secretary of the Interior, through the National Park Service, to be “certified historic structures.” The State Historic Preservation Offices and the National Park Service review the rehabilitation work to ensure that it complies with the Secretary’s Standards for Rehabilitation. The Internal Revenue Service defines qualified rehabilitation expenses on which the credit may be taken. Owner-occupied residential properties do not qualify for the federal rehabilitation tax credit. Learn more about this credit before you apply.

Each year, Technical Preservation Services approves approximately 1000 projects, leveraging nearly $4 billion annually in private investment in the rehabilitation of historic buildings across the country.

10% Tax Credit

The 10% tax credit is available for the rehabilitation of non-historic buildings placed in service before 1936. The building must be rehabilitated for non-residential use. In order to qualify for the tax credit, the rehabilitation must meet three criteria: at least 50% of the existing external walls must remain in place as external walls, at least 75% of the existing external walls must remain in place as either external or internal walls, and at least 75% of the internal structural framework must remain in place. There is no formal review process for rehabilitations of non-historic buildings. Learn more about this credit in Historic Preservation Tax Incentives.

Tax Benefits for Historic Preservation Easements

A historic preservation easement is a voluntary legal agreement, typically in the form of a deed, that permanently protects an historic property. Through the easement, a property owner places restrictions on the development of or changes to the historic property, then transfers these restrictions to a preservation or conservation organization. A historic property owner who donates an easement may be eligible for tax benefits, such as a Federal income tax deduction. Easement rules are complex, so property owners interested in the potential tax benefits of an easement donation should consult with their accountant or tax attorney. Learn more about easements in Easements to Protect Historic Properties: A Useful Historic Preservation Tool with Potential Tax Benefits.

The following information pertains to the 20% federal tax credit for the rehabilitation of historic properties.

Tax Credit Basics

• The amount of credit available under this program equals 20% of the qualifying expenses of your rehabilitation.
• The tax credit is only available to properties that will be used for a business or other income–producing purpose, and a "substantial" amount must be spent rehabilitating the historic building.
• Your building needs to be certified as a historic structure by the National Park Service.
• Rehabilitation work has to meet the Secretary of the Interior’s Standards for Rehabilitation, as determined by the National Park Service.

Before applying, consult your accountant or tax advisor to make sure that this federal tax credit is beneficial to you. Certain income and other restrictions may have a bearing on whether an owner is able to use the credit. IRS administers the Department of the Treasury’s involvement with the Federal Historic Preservation Tax Incentives Program. The IRS has provided written guidance on these complex federal regulations which is available as easy-to-read guidance in IRS Info.

Partnership Program

The tax incentives program is administered by the National Park Service (NPS) and the Internal Revenue Service (IRS) in partnership with the State Historic Preservation Offices (SHPOs). Each plays a specific role:

SHPOs

• Serve as first point of contact for property owners.
• Provide application forms, regulations, information on appropriate treatments, and technical assistance.
• Maintain records of buildings and districts listed in the National Register of Historic Places, as well as state and local certified historic districts.
• Assist anyone wishing to list a building or a district in the National Register of Historic Places.
• Advise applicants on rehabilitation projects and make site visits.
• Make certification recommendations to the NPS.

NPS

• Reviews applications for conformance with the Secretary of the Interior’s Standards for Rehabilitation.
• Issues certification decisions in writing.
• Transmits copies of all decisions to the IRS.
• Publishes program regulations, the Secretary of the Interior’s Standards for Rehabilitation, the Historic Preservation Certification Application, and information on rehabilitation treatments.

IRS

• Publishes regulations on qualified rehabilitation expenses, time periods for incurring expenses, and all other financial matters concerning the 20% tax credit.
• Answers inquiries on financial aspects of the program, and publishes an audit guide to assist owners.
• Audits taxpayers to ensure that only parties eligible for the 20% tax credits use them.

Eligibility Requirements

There are 4 factors that can help you decide whether your rehabilitation project would meet the basic requirements for the 20% tax credit.

Diary of a preservation contractor 14-Nov-2011

 Email Article  

  

  

 delicious  

  

Today's travels took me north into the Adirondacks, visiting our prior clients at the Ticonderoga Historical Society.  Their building houses a museum, an art gallery, and priceless artifacts, antiques, and local history treasures.  The last time we were there in May of 2006, work was limited to plaster restoration.  Now water is getting inside, threatening to ruin our plaster work and the countless treasures mentioned.  As a courtesy, an abbreviated conditions assessment was prepared so funding can be sought.  Estimates of cost have been withheld out of courtesy to the client.   

BUILDING CONDITIONS ASSESSMENT

Specific to roofing, flashing details and gutter linings

Ticonderoga Historical Society

Hancock House

6 Moses Circle

Ticonderoga, NY 12883

14 November 2011

CONTEXT

The Hancock House is an historic structure in Ticonderoga, New York. It is a replica of the Hancock Manor on Boston's Beacon Hill that was the residence of Thomas Hancock, the uncle of John Hancock.  The Hancock House was built by philanthropist Horace A. Moses for the New York State Historical Association as a repository for "American Traditions in History and the Fine Arts."  The Association used it as its "Headquarters House" until after World War II.  Built in 1925, the structure was added to the National Register of Historic Places (reference no. 88002197) on November 15, 1988.

HISTORY

Born in Ticonderoga, Horace Augustus Moses became wealthy building and acquiring a number of paper mills that he combined to form the Strathmore Paper Company. As his wealth grew, he made a series of substantial donations to many Ticonderoga projects, among which were the Valley View Cemetery Chapel, the Liberty Monument, the Moses-Ludington Hospital, the Community Building, and the Hancock House; with the last of these, he accomplished an early lifetime ambition— to establish a museum with a library that would make Ticonderoga a focal point for public interest in the region's history.

The Hancock House Museum and Research Library was established in 1926. The Ticonderoga Historical Society today manages the building as a regional museum and reference library. There are exhibits throughout the Hancock House. The library houses a large collection of regional material on civic, social and economic matters and has one of the largest collections of genealogical resource materials in the region.

STRUCTURE

The Hancock Manor House was demolished in 1863 to make room for an expansion of the Massachusetts State House. The razing of the Hancock House in Boston is often viewed as a predicate offense that spurred the organization of the Society for the Preservation of New England Antiquities (present day Historic New England.)  The main hall and stairway and the two rooms to the right of the hall are exact duplicates of those in the original house.  Architects of the extant structure in Ticonderoga were M.H. Westhoff and Edward F. Minor. 

While the original house was built of Weymouth (Massachusetts) granite, the house in Ticonderoga was built with Corinthian granite (Washington County, NY), from drawings made by John Sturgis before the original house was destroyed.  The gambrel roof is a blend of Vermont (green, gray and purple) and New York (red) roofing slates.  Approximately twelve (12) slates are broken; none are completely missing.  The six dormer roofs, gutter linings, conductor pipes, vents, and flashing details are all red copper.  Save for part of the counter-flashing on the four chimneys and the gutter linings (and conductor pipes), the copper all appears to be original to the construction of the building.

WATER INFILTRATION

This firm was contacted on November 11, 2011, in reference to water damage found in the second and third floors of the Hancock House.  On November 14, 2011, the roofing, gutters, attic, second and third floors were inspected.  Water damage to plaster was found in the third floor locations corresponding with chimney and balustrade flashing details, above.  At the rear, center dormer, it appears that valley flashing details are failing.  This is especially problematic because the standing-seam copper, barrel-style dormer roof ties into this detail.  The valley cannot be replaced without “undoing” the brittle copper roofing, necessitating a larger project.  Additionally, a failure on the gutter lining has allowed a large amount of water into a second story museum space causing extensive damage to the plaster molding profiles of the cornice, including the loss of entire modillions.

RECOMMENDATIONS

The copper flashings and roofing, which are original to the roof’s construction, have been in place for over eighty-five years.  Copper has a service life of eighty to one hundred years, and this copper is failing.  When preserving the heritage of our built environment, it is critical that we preserve the historic fabric of a structure.  According to the ‘Secretary of the Interior’s Standards for the Treatment of Historic Properties with Illustrated Guidelines for Preserving, Rehabilitating, Restoring, and Reconstructing Historic Buildings,’ when an element has failed and must be replaced, replacement materials must be in kind when still available. Our recommendation is for the total replacement of the copper flashing details, vents and dormer roofs.  Also, of critical importance, the broken solder joints in the gutter linings must be repaired to prevent further internal damage. 

Traditional Roofing Materials: Clay tile

 Email Article  

  

  

 delicious  

  

Clay tiles are one of the most distinctive and decorative historic roofing materials because of their great variety of shapes, colors, profiles, patterns, and textures. Traditionally, clay tiles were formed by hand, and later by machine extrusion of natural clay, textured or glazed with color, and fired in high-temperature kilns. The unique visual qualities of a clay tile roof often make it a prominent feature in defining the overall character of a historic building. The significance and inherently fragile nature of historic tile roofs dictate that special care and precaution be taken to preserve and repair them.

Clay tile was a popular roofing material for residential structures during the Romanesque Revival period. Photo: NPS files.

Clay tile has one of the longest life expectancies among historic roofing materials-generally about 100 years, and often several hundred. Yet, a regularly scheduled maintenance program is necessary to prolong the life of any roofing system. A complete internal and external inspection of the roof structure and the roof covering is recommended to determine condition, potential causes of failure, or source of leaks, and will help in developing a program for the preservation and repair of the tile roof. Before initiating any repair work on historic clay tile roofs, it is important to identify those qualities important in contributing to the historic significance and character of the building.

This Brief will review the history of clay roofing tiles and will include a description of the many types and shapes of historic tiles, as well as their different methods of attachment. It will conclude with general guidance for the historic property owner or building manager on how to plan and carry out a project involving the repair and selected replacement of historic clay roofing tiles.

Historical Background

The origin of clay roofing tile can be traced independently to two different parts of the world: China, during the Neolithic Age, beginning around 10,000 B.C.; and the Middle East, a short time later. From these regions, the use of clay tile spread throughout Asia and Europe. Not only the ancient Egyptians and Babylonians, but also the Greeks and Romans roofed their buildings with clay tiles, and adaptations of their practice continue in Europe to the present. European settlers brought this roofing tradition to America where it was established in many places by the 17th century.

Tapered barrel clay roof tiles were custom made for the restoration of the 1820s Indian barracks at Mission Santa Cruz in California. Photo: NPS files.

Archeologists have recovered specimens of clay roofing tiles from the 1585 settlement of Roanoke Island in North Carolina. Clay tile was also used in the early English settlements in Jamestown, Virginia, and nearby St. Mary's in Maryland. Clay roofing tiles were also used in the Spanish settlement of St. Augustine in Florida, and by both the French and Spanish in New Orleans.

Dutch settlers on the east coast first imported clay tiles from Holland. By 1650, they had established their own full-scale production of clay tiles in the upper Hudson River Valley, shipping tiles south to New Amsterdam. Several tile manufacturing operations were in business around the time of the American Revolution, offering both colored and glazed tile and unglazed natural terra-cotta tile in the New York City area, and in neighboring New Jersey. A 1774 New York newspaper advertised the availability of locally produced, glazed and unglazed pantiles for sale that were guaranteed to "stand any weather." On the west coast clay tile was first manufactured in wooden molds in 1780 at Mission San Antonio de Padua in California by Indian neophytes under the direction of Spanish missionaries.

By far the most significant factor in popularizing clay roofing tiles during the Colonial period in America was the concern with fire. Devastating fires in London, 1666, and Boston in 1679, prompted the establishment of building and fire codes in New York and Boston. These fire codes, which remained in effect for almost two centuries, encouraged the use of tile for roofs, especially in urban areas, because of its fireproof qualities. Clay roofing tile was also preferred because of its durability, ease of maintenance, and lack of thermal conductivity.

Although more efficient production methods had lowered the cost of clay tile, its use began to decline in much of the northeastern United States during the second quarter of the 19th century. In most areas outside city-designated fire districts, wood shingles were used widely; they were more affordable and much lighter, and required less heavy and less expensive roof framing. In addition, new fire-resistant materials were becoming available that could be used for roofing, including slate, and metals such as copper, iron, tin-plate, zinc, and galvanized iron. Many of the metal roofing materials could be installed at a fraction of the cost and weight of clay tile. Even the appearance of clay tile was no longer fashionable, and by the 1830s clay roofing tiles had slipped temporarily out of popularity in many parts of the country.

Revival Styles Renew Interest in Clay Roofing Tiles

By the mid-19th century, the introduction of the Italianate Villa style of architecture in the United States prompted a new interest in clay tiles for roofing. This had the effect of revitalizing the clay tile manufacturing industry, and by the 1870s, new factories were in business, including large operations in Akron, Ohio, and Baltimore, Maryland.

The clay tile roof is important in defining the character of the c. 1917 Mission-style Grove Park Inn, Asheville, North Carolina. Photo: NPS files.

Alternative substitutes for clay tiles were also needed to meet this new demand. By about 1855, sheet metal roofs designed to replicate the patterns of clay tile were being produced. Usually painted a natural terra cotta color to emulate real clay tile, these sheet metal roofs became popular because they were cheaper and lighter, and easier to install than clay tile roofs.

Clay tiles emphasize the prominence of the peaked roofs of these late 19th century rowhouses. Photo: NPS files.

Clay roofing tiles fell out of fashion again for a short time at the end of the 19th century, but once more gained acceptance in the 20th century, due primarily to the popularity of the Romantic Revival architectural styles, including Mission, Spanish, Mediterranean, Georgian and Renaissance Revival in which clay tile roofs featured prominently. With the availability of machines capable of extruding clay in a variety of forms in large quantities, clay tiles became more readily available across the nation. More regional manufacturing plants were established in areas with large natural deposits of clay, including Alfred, New York; New Lexington, Ohio; Lincoln, California; and Atlanta, Georgia; as well as Indiana, Illinois and Kansas.

The popularity of clay tile roofing, and look-alike substitute roofing materials, continues in the 20th century, especially in areas of the South and West-most notably Florida and California--where Mediterranean and Spanish--influenced styles of architecture still predominate.

Early Tiles

During the 17th and 18th centuries the most common type of clay roofing tiles used in America were flat and rectangular. They measured approximately 10" x 6" x ½" (25cm x 15cm x 1.25cm), and had two nail or peg holes at one end through which they were anchored to the roofing laths. Sometimes a strip of mortar was placed between the overlapping rows of tile to prevent the tiles from lifting in high winds. In addition to flat tiles, interlocking S-shaped pantiles were also used in the 18th century. These were formed by molding clay over tapered sections of logs, and were generally quite large. Alternately termed pan, crooked, or Flemish tiles, and measuring approximately 14 ½" x 9 ½" (37cm x 24cm), these interlocking tiles were hung on roofing lath by means of a ridge or lug located on the upper part of the underside of each tile. Both plain (flat) tile and pantile (S-shaped or curved) roofs were capped at the ridge with semicircular ridge tiles. Clay roofing tiles on buildings in mid-18th century Moravian settlements in Pennsylvania closely resembled those used in Germany at the time. These tiles were about 14"-15" long x 6"-7" wide (36cm-38cm x 15cm-18cm) with a curved butt, and with vertical grooves to help drainage. They were also designed with a lug or nib on the back so that the tiles could hang on lath without nails or pegs.

The accurate dating of early roofing tiles is difficult and often impossible. Fragments of tile found at archeological sites may indicate the existence of clay tile roofs, but the same type of tile was also sometimes used for other purposes such as paving, and in bake ovens. To further complicate dating, since clay tile frequently outlasted many of the earliest, less permanent structures, it was often reused on later buildings.

Preservation and Repair

Identifying Common Problems and Failures

While clay roofing tiles themselves are most likely to deteriorate because of frost damage, a clay tile roof system most commonly fails due to the breakdown of the fastening system. As the wooden pegs that fastened the early tiles to hand-riven battens rotted, they were often replaced with iron nails which are themselves easily corroded by tannic acid from oak battens or sheathing. The deterioration of metal flashing, valleys, and gutters can also lead to the failure of a clay tile roof.

Another area of potential failure of a historic clay tile roof is the support system. Clay tiles are heavy and it is important that the roof structure be sound. If gutters and downspouts are allowed to fill with debris, water can back up and seep under roofing tiles, causing the eventual deterioration of roofing battens, the sheathing and fastening system, or even the roof's structural members. During freezing weather, ice can build up under tiles and cause breakage during the freeze/thaw cycle. Thus, as with any type of roof, water and improperly maintained rainwater removal and drainage systems are also chief causes for the failure of historic clay tile roofs.

Clay tiles may be either handcrafted or machine-made; in general, roofs installed before the end of the 19th century consist of hand formed tiles, with machine-made tiles becoming more dominant as technology improved during the 20th century. Clay tile itself, whether made by hand or made by machine, can vary in quality from tile to tile. Efflorescence of soluble salts on the surface may indicate that a tile has excessive porosity which results from under-burning during its manufacture. Poor quality porous tiles are particularly susceptible to breaking and exterior surface spalling during freeze-thaw cycles. By letting in moisture, porous tiles can permit the roof battens and roof structure to rot. The problem may be compounded by waterproof building paper or building felt laid underneath which can, in some instances, prevent adequate ventilation.

Clay roofing tiles can also be damaged by roofers walking carelessly on an unprotected roof while making repairs, or by overhanging tree branches, falling tree limbs, or heavy hail. Broken tiles may no longer provide a continuous waterproof surface, thereby allowing water to penetrate the roofing structure, and may eventually result in its deterioration if the broken tiles are not replaced in a timely manner.

Although modern, machine-made clay tiles are more uniform in appearance than their handmade counterparts, they also have the potential for failure. Occasionally, entire batches of mass-produced tile can be defective.

Regular Inspection and Maintenance

A special system consisting of brass or copper wires is used to attach these tapered barrel roof tiles. Photo: NPS files.

Broken or missing tiles, or leaks on the interior of the building, are obvious clues that a historic clay tile roof needs repair. Even though it may be clear that the roof is leaking, finding the source of the leak may not be so easy. It may require thorough investigation in the attic, as well as going up on the roof and removing tiles selectively in the approximate area of the roof leak. The source of the leak may not actually be located where it appears to be. Water may come in one place and travel along a roofing member some distance from the actual leak before revealing itself by a water stain, plaster damage, or rotted wooden structural members.

Temporary Protection during Repair

In some instances temporary protection and stabilization may be necessary to prevent further damage or deterioration of a historic clay tile roof. Plywood sheets, plastic, roll roofing, or roofing felt can provide short-term protection until repair or replacement materials can be purchased. Another option may be to erect a temporary scaffold that is encased or covered with clear or semitransparent polyethylene sheeting over the entire roof. This will not only protect the exposed roofing members during repair or until repairs can be made, but also lets in enough natural light to enable the reroofing work to take place while sheltering workmen from cold or wet weather.

General Repair Guidance

Once the source and cause of a leak has been identified, appropriate repairs must be made to structural roofing members, wood sheathing, felt or roofing paper if it is part of the roofing membrane, or possibly to vertical roof battens to which the tiles may be attached. If the problem appears limited to gutters and flashing in disrepair, repair or replacement will probably require temporary removal of some of the adjacent tiles to gain access to them. If the roofing tiles are extremely fragile and cannot be walked on even with adequate protection (see below), it may also be necessary to remove several rows or a larger area of tiles and store them for later reinstallation in order to create a "path" to reach the area of repair without damaging existing tiles. Even if most of the tiles themselves appear to be intact but no longer securely attached to the roof substrate due to deterioration of the fastening system or roofing members, all the tiles should be labeled and removed for storage. Regardless of whether the repair project involves removal of only a few damaged tiles, or if all the tiles must be removed and relaid, historic clay roofing tiles are inherently fragile and should be pulled up carefully with the use of a slate ripper. The tiles can be reattached one-by-one with new corrosion-resistant copper nails, copper straps or tabs, "tingles', or another means after the necessary repairs have been made to the roof.

Replacing Individual Tiles

The most difficult aspect of replacing a single broken clay roof tile is doing so without breaking neighboring tiles. While flat shingle tiles can generally be walked on by a careful roofer without likelihood of much damage, high profile pantiles are very fragile and easily broken. By using sheets of plywood, planks, or burlap bags filled with sand to distribute weight, the professional roofer can move about the roof to fix broken tiles or flashing without causing additional damage. Another method involves hooking a ladder on the ridge to support and evenly distribute the weight of the roofer.

A broken tile should be carefully removed with a slate ripper or hacksaw blade inserted under the tile to cut the nail or nails holding it in place. If successive layers of tile are already in place covering the nailholes, it will not be possible to attach the replacement tile with nails through the holes, so an alternative method of attachment will be necessary. By nailing a tab of double thickness copper stripping on the sheathing below the tile, the new replacement tile can be slipped into position and secured in place by bending the copper strip up with a double thickness of the copper over the tile. A slate hook or "tingle" can be used in the same way. This fastening system functions in place of nails.

When replacing hard-to-match historic tile, and if matching clay tile cannot be obtained, it may be possible to relocate some of the original tiles to the more prominent locations on the roof where the tile is damaged, and insert the new replacement tile in secondary or rear locations, or other areas where it will not show, such as behind chimney stacks, parapets, and dormer windows. Even though replacement tile may initially match the original historic tile when first installed, it is likely to weather or age to a somewhat different color or hue which will become more obvious with time. Thus, care should be taken to insert new replacement tile in as inconspicuous a location as possible. New, machine-made clay tile or concrete tiles should generally not be used to patch roofs of old, handmade tile because of obvious differences in appearance.

Sources for Replacement Tiles

When restoring or repairing a clay tile roof it is always recommended that as many of the original tiles be retained and reused as possible. Sometimes, particularly when working with "pan and cover" type tile roofs, while many of the "cover" tiles may be broken and require replacement, it may be possible to reuse all or most of the "pan" tiles which are less susceptible to damage than the "cover" tiles. But, in most cases, unless matching replacements can be obtained, if more than about 30 per cent of the roofing tiles are lost, broken, or irreparably damaged, it may be necessary to replace all of the historic tiles with new matching tiles. When counting the number or percentage of missing or broken tiles that need to be replaced, it is important to order extra tiles to allow for breakage and damage during shipping and on the job site. The size of the tiles must be noted, whether they are all the same size, the same size but laid with different amounts of exposure to compensate for changes in perspective, or of graduated sizes according to horizontal rows-typical, for example, on conical or tower roofs.

Many late-19th and early-20th century tiles are marked on the back with the name of the company that made them, along with the size and the name of that particular tile shape. Some companies that were in business in the United States at the turn of the century are still producing many of the traditional tile shapes, and may be able to supply the necessary replacements. But it is important to be aware that in some cases, although the name of a particular tile pattern may have remained the same, the actual shape, size, thickness and profile may have changed slightly so that the new tile does not match the historic tile closely enough to permit it to serve as a compatible replacement for missing or broken tiles. While such tiles may be acceptable to use on a secondary or less prominent elevation, or to use when an entire tile roof needs replacement, they would not be suitable to use on an area of the roof that is highly visible.

Even if the particular tile is no longer manufactured by a company, the original molds may still exist which can be used to make new tiles to match the historic tiles if the quantity needed is sufficiently large to warrant a custom order. Other companies stock and sell salvaged tile, and keep a variety of old tiles available which can be identified and matched by the number and company imprint on the back of the tiles. Still other companies specialize entirely in custom-made reproduction of historic clay tiles for a specific preservation project.

Modern clay tiles are even more varied than historic tiles. Many shapes and styles are offered in a wide variety of colors and glazes. Several manufacturers produce special color-blended tiles, as well as tiles of different hues that are intended to be carefully mixed when installed. Yet, it is important to remember that many of these modern tiles may not be appropriate for use on historic clay tile roofs. The place of manufacture must also be taken into consideration. For instance, tiles made for use in a hot, dry climate may not be able to withstand wet weather, drastic temperature changes or freeze-thaw cycles. Some of the tile shapes, and many of the colors-especially those that are very bright and highly glazed-are completely contemporary in design, and do not represent traditional American styles, and thus, are not suitable for use on historic buildings.

Repairing a Failed Fastening System

Clay roofing tiles, as noted before, frequently outlast their fastening systems. Wood pegs rot, nails rust, and even copper nails that are not adequately driven in can pull out of the roof's structural members. Although it is unusual that all of the clay tiles on a roof need to be replaced unless matching replacements cannot be obtained, it is not uncommon for old tile roofs to be stripped of all their tiles in order to relay the tiles with new fastenings and battens. When the fastening system has failed, all the roof tiles must be removed and reattached with new corrosion-resistant fasteners. If possible, all the tiles should be numbered and a diagram should be drawn showing the location of each tile to aid in replicating the original pattern and color variations when the tiles are relaid. Ideally, each tile should be numbered to ensure that it is reinstalled in its original location. But this may not always be feasible or practical, and it may be enough simply to group the tiles as they are removed by type and size or function-such as field tiles, custom tiles for hips, dormers and ridges, and specially cut pieces. This will help facilitate reinstallation of the tiles. If all of the tiles have to be removed, it is probably a good idea to consider installing a layer of modern roofing felt over the wood sheathing. This will add another layer of waterproofing, while providing temporary protection during reroofing.

Even if the tiles were originally attached with wooden pegs, it is generally recommended that they be rehung with corrosion-resistant, preferably heavy copper, or aluminum alloy nails or hooks. Today there are numerous nontraditional fastening systems for clay tile roofs, and many of them are patented. Roofing contractors and architects may have individual preferences, and some systems may be better suited than others to fit a particular roof shape or to meet a specific climatic or seismic requirement. Original battens or other roof members that may have deteriorated should be replaced to match the original using pressure-treated wood. Additional support may be necessary, particularly if the original roof was inadequate or poorly designed.

Replacing Flashing

Deteriorated flashing, gutters and downspouts should generally be replaced in kind to match the historic material. Copper or lead-coated copper, if appropriate to the building, or terne-coated stainless steel, is often preferred for use on historic clay tile roofs because of their durability and long lasting qualities. However, copper staining from downspouts can sometimes be a problem on light-colored masonry walls which should be taken into consideration when planning replacements to rainwater removal systems. Clay tile roofs usually have an open valley system where the tiles are separated by metal flashing at intersections of roof sections with different angles. This makes the insertion of new flashing quite easy, as only a few surrounding tiles must be removed in the process. New copper flashing that is too "bright" can be made to blend in and "mellowed" by brush-coating it with boiled linseed oil or proprietary solutions.

Inappropriate Repairs

The most important repair to avoid is replacing broken or missing roof tiles on a historic building with materials other than matching natural clay tiles. Concrete, metal or plastic tiles are generally not appropriate substitutes for clay roofing tiles. They lack the natural color variations of clay tile, and they do not have the same texture, shape, thickness or surface irregularities.

Although much concrete tile and composition tile is produced to resemble the general shape, if not the exact profile, of clay roofing tiles, concrete tile is generally too thick and also lacks the range of colors inherent in natural clay tile. Concrete tile is not a compatible substitute material to repair or replace individual historic clay tiles.

Patching a historic clay tile roof with roofing tar, caulk, asphalt, pieces of metal, or non-matching clay tiles is also inappropriate. Such treatments are visually incompatible. They also have the potential for causing physical damage. Water can collect behind these patches, thus accelerating deterioration of roof sheathing and fastening systems, and during the expansion and contraction of a freeze-thaw cycle ice buildup at patches can break surrounding tiles.

Source:  TPS #30  This article has been prepared pursuant to the National Historic Preservation Act of 1966, as amended, which directs the Secretary of the Interior to develop and make available information concerning historic properties. Technical Preservation Services (TPS), Heritage Preservation Services Division, National Park Service prepares standards, guidelines, and other educational materials on responsible historic preservation treatments for a broad public.

Traditional Roofing Materials: Historic uses of tile

 Email Article  

  

  

 delicious  

  

Roof tiles are designed mainly to keep out rain, and are traditionally made from locally available materials such as clay or slate. Modern materials such as concrete and plastic are also used and some clay tiles have a waterproof glaze. A large number of shapes (or "profiles") of roof tiles have evolved. These include:

• Flat tiles - the simplest type, which are laid in regular overlapping rows. An example of this is the clay-made "beaver-tail" tile (German Biberschwanz), common in Southern Germany. Flat roof tiles are usually made of clay but also may be made of stone, wood, plastic, concrete, or solar cells.
• Imbrex and tegula, an ancient Roman pattern of curved and flat tiles that make rain channels on a roof.
• Roman tiles - flat in the middle, with a concave curve at one end at a convex curve at the other, to allow interlocking.
• Pantiles - with an S-shaped profile, allowing adjacent tiles to interlock. These result in a ridged pattern resembling a ploughed field. An example of this is the "double Roman" tile, dating from the late 19th century in England and USA.
• Mission or barrel tiles are semi-cylindrical tiles laid in alternating columns of convex and concave tiles. Originally they were made by forming clay around a curved surface, often a log or the maker's thigh. Today barrel tiles are mass produced from clay, metal, concrete or plastic.
• Interlocking roof tiles are similar to pantile with side and top locking to improve protection from water and wind.

Roof tiles are 'hung' from the framework of a roof by fixing them with nails. The tiles are usually hung in parallel rows, with each row overlapping the row below it to exclude rainwater and to cover the nails that hold the row below. There are also roof tiles for special positions, particularly where the planes of the several pitches meet. They include ridge, hip and valley tiles.

Similarly to roof tiling, tiling has been used to provide a protective weather envelope to the sides of timber frame buildings. These are hung on laths nailed to wall timbers, with tiles specially moulded to cover corners and jambs. Often these tiles are shaped at the exposed end to give a decorative effect. Another form of this is the so-called mathematical tile, which was hung on laths, nailed and then grouted. This form of tiling gives an imitation of brickwork and was developed to give the appearance of brick, but avoided the Brick Taxes of the 18th century.

The earliest finds of roof tiles in archaic Greece are documented from a very restricted area around Corinth (Greece), where fired tiles began to replace thatched roofs at two temples of Apollo and Poseidon between 700-650 BC. Spreading rapidly, roof tiles were within fifty years in evidence for a large number of sites around the Eastern Mediterranean, including Mainland Greece, Western Asia Minor, Southern and Central Italy. Early roof tiles showed an S-shape, with the pan and cover tile forming one piece. They were rather bulky affairs, weighing around 30 kg apiece. Being more expensive and labour-intensive to produce than thatch, their introduction has been explained by their greatly enhanced fire resistance which gave desired protection to the costly temples.

The spread of the roof tile technique has to be viewed in connection with the simultaneous rise of monumental architecture in ancient Greece. Only the appearing stone walls, which were replacing the earlier mudbrick and wood walls, were strong enough to support the weight of a tiled roof. As a side-effect, it has been assumed that the new stone and tile construction also ushered in the end of 'Chinese roof' (Knickdach) construction in Greek architecture, as they made the need for an extended roof as rain protection for the mudbrick walls obsolete.

Production of dutch roof tiles started in the 14th century when city rulers required the use of fireproof materials. At the time most houses were made of wood and had thatch roofing, which would often cause fires to quickly spread. To satisfy demand, many small roof tile makers began to produce roof tiles by hand. Many of these small factories were built near rivers where there was a ready source of clay and cheap transport.

Sustainable Preservation: Greening Existing Buildings

 Email Article  

  

  

 delicious  

  

Jean Carroon has crafted a guide to green strategies for preservation and adaptive reuse—and the power of preservation/reuse as a green strategy.

Buildings account for nearly forty percent of both total energy use and carbon emissions in the United States. With one of the country's leading preservation architects as your guide, Sustainable Preservation explores the power of adaptive reuse to reduce those numbers and move us toward sustainability. It shows how an icon such as H.H. Richardson's Trinity Church in Boston can go green—and why a 1970s strip-mall supermarket not only deserves similar attention but can also emerge as a building that delights users.

Sustainable Preservation takes a nuanced look at the hundreds of choices that adaptive reuse requires architects to make—from ingenious ways to redeploy existing structural elements to time-honored techniques for natural ventilation to creation of wetlands that restore a site's natural biological functions. In addition, Sustainable Preservation:

• Presents fifty case studies of projects—schools, houses, offices, stores, museums, and government buildings—that set new standards for holistic approaches to adaptive reuse and sustainability

• Covers design issues, from building location to lighting systems, renewable power options, stormwater handling, and building envelope protection and integrity.

• Reviews operational issues, including materials choices for low lifetime maintenance, green housekeeping, and indoor air quality

• Explains calculators and programs that supplement the LEED® green building certification program requirements to yield even greater environmental benefits

Sustainable Preservation makes a compelling argument that preservation and sustainability don't just protect the environment, but deliver a full range of societal benefits, from job creation to stronger social connection.

Traditional Roofing Materials: Thatch

 Email Article  

  

  

 delicious  

  

Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge (Cladium mariscus), rushes, or heather, layering the vegetation so as to shed water away from the inner roof. It is a very old roofing method and has been used in both tropical and temperate climates. Thatch is still employed by builders in developing countries, usually with low-cost, local vegetation. By contrast in some developed countries it is now the choice of affluent people who desire a rustic look for their home or who have purchased an originally thatched abode.

In most of Europe and the UK, thatch remained the only roofing material available to the bulk of the population in the countryside, and in many towns and villages, until the late 1800s. The commercial production of Welsh slate had begun in 1820 and the mobility which the canals and then the railways made possible meant that other materials became readily available. The number of thatched properties actually increased in the UK during the mid-1800s as agriculture expanded, but then declined again at the end of the 19th century because of agricultural recession and rural depopulation. Gradually, thatch became a mark of poverty and the number of thatched properties gradually declined, as did the number of professional thatchers.

Thatch has become much more popular in the UK over the past 30 years, and is now a symbol of wealth rather than poverty. There are now approximately 1,000 full time thatchers at work in the UK, and thatching is becoming popular again because of the renewed interest in preserving historic buildings and using more sustainable building materials.

There are more thatched roofs in the United Kingdom and Ireland than in any other European country. Good quality thatching straw can last for more than 45–50 years when applied by a skilled thatcher. Traditionally, a new layer of straw was simply applied over the weathered surface, and this ‘spar coating’ tradition has created accumulations of thatch over 7’ (2.1 m) thick on very old buildings. Over 250 roofs in Southern England have base coats of thatch that were applied over 500 years ago, providing direct evidence of the types of materials that were used for thatching in the medieval period. Almost all of these roofs are thatched with wheat, rye, or a 'maslin' mixture of both. Medieval wheat grew to almost 6 feet (1.8 m) tall in very poor soils and produced durable straw for the roof and grain for baking bread. Information on UK thatching materials, methods and traditions, and the work that is being done to preserve them, is available on the Conservation of Historic Thatch website.

Technology in the farming industry has had a significant impact on the popularity of thatching. The availability of good quality thatching straw declined in England after the introduction of the combine harvester in the late 1930s and 1940s, and the release of short-stemmed wheat varieties. The increasing use of nitrogen fertiliser in the 1960s-70s also weakened straw and reduced its longevity. Since the 1980s, however, there has been a big increase in straw quality as specialist growers have returned to growing older, tall-stemmed, 'heritage' varieties of wheat such as Maris Wigeon, in low input/organic conditions.

All of the evidence indicates that water reed was rarely used for thatching outside of East Anglia. It has traditionally been a 'one coat' material applied in a similar way to how it is used in continental Europe - weathered reed is usually stripped and replaced by a new layer. It takes 4-5 acres of well-managed reed bed to produce enough reed to thatch an average house, and large reed beds have been uncommon in most of England since the Anglo-Saxon period. Over 80% of the water reed used in the UK is now imported from Turkey, Eastern Europe and China. Although water reed might last for 50 years or more on a steep roof in a dry climate, modern imported water reed on an average roof in England will not last any longer than good quality wheat straw. The lifespan of a thatched roof is also dependent on the skill of the thatcher, but other factors need to be taken into account, such as climate, quality of the materials used, and the pitch of the roof.

In areas where palms are abundant, palm leaves are used to thatch walls and roofs. Many species of palm trees are called "thatch palm", or have "thatch" as part of their common names. In the southeastern United States, Indian and pioneer houses were often constructed of palmetto-leaf thatch. The chickees of the Seminole and Miccosukee Indians are still thatched with palmetto leaves.

The thickness of the thatch decreases over the years as the surface is gradually eroded. A thatched roof can be thought to be nearing replacement when the horizontal fixings of each course are close to the surface. “A roof is as good as the amount of correctly laid thatch covering the fixings.” Thatching materials range from plains grasses to waterproof leaves found in equatorial regions. It is the most common roofing material in the world, because the materials are readily available.

Because thatch is lighter less timber is required in the roof that supports it.  Thatch is a versatile material when it comes to covering irregular roof structures. This fact lends itself to the use of second-hand, recycled and natural materials that are not only more sustainable, but need not fit exact standard dimensions to perform well.

Managing moisture in your historic home

 Email Article  

  

  

 delicious  

  

Water, water everywhere! Without argument, it's essential to us. But in terms of the places where we live or work, unwanted moisture means erosion, corrosion and rot! This mini-web class can help anyone who cares for, or about, a historic house to better understand and deal with the three most common sources of the "wet stuff."

  Learn how they invade historic materials:

•   From the outside "in"
•   From the ground "up"
•   From "within" the interior itself.

 We'll show you what goes wrong when moisture is not adequately managed  and how to turn the corner on present and future problems by providing some simple, common sense tips.

Moisture as home-wrecker.
Most moisture problems are the result of rain or snow, high humidity, or high water tables. But some of the most troublesome moisture damage in older houses can be caused inside the house by leaky plumbing, heaters and air conditioners, as well simply cooking and doing laundry. Taken as a whole, the wet invaders can control your house unless you manage them!

It's good to understand the forces that move air and moisture through a building so you can better identify and correct a problem. The drawing shows how moisture can invade "inward" from the exterior; "upward" from the ground; and be generated from "within" the interior. All have damaging effects.

A Little Science.
You probably already know moisture moves both as liquid and as vapor. This movement is directly related to differences in pressure.

For example, water as vapor--warm moist air--moves from a high pressure area to a lower pressure area where the air is cooler and drier. Liquid water moves as a result of differences in hydrostatic pressure or wind pressure.

How fast moisture moves depends on how permeable the building materials are and how quickly water is absorbed. More formal terminology may be used to describe moisture movement and how it invades a house: lateral penetration (from the outside of the house in), capillary action (wicking up from the ground), and vapor diffusion (condensation within the house's interior). The subject is infinitely complex and, thus, one of continuing scientific study.

  Watch out for these disgusting signs.
Identifying the problem and discovering its source or sources (from the outside, the ground, or within) usually involves the human senses of sight, smell, hearing, touch, and taste! Here are some of the more common signs of visible--as well as hidden--moisture damage:

* Presence of standing water, mold, fungus, or mildew

* Wet stains, eroding surfaces, or efflorescence (salt deposits) on interior and exterior surfaces

* Flaking paint and plaster, peeling wallpaper, or moisture blisters on finished surfaces

* Dank, musty smells in areas of high humidity or poorly ventilated spaces

* Rust and corrosion stains on metal elements, such as anchorage systems and protruding roof nails in the attic

* Cupped, warped, cracked, or rotted wood

* Spalled, cracked masonry or eroded mortar joints

* Faulty roofs and gutters including missing roofing slates, tiles, or shingles and poor condition of flashing or gutters

* Condensation on window and wall surfaces

* Ice dams in gutters, on roofs, or leaks in the attics

Moisture invasion from the outside "in" ...

Historic houses are notoriously "drafty." They can easily allow rain and damp airto enter   through missing mortar in brick or stone and through cracks around windows and doors. In the winter, snow and ice can be particuarly damaging. Ice dams that form in roof gutters can lift up roofing tiles, allowing the ice to melt into attics and exterior walls. Often, deterioration caused by the weather will be evident on the interior before you ever see it on the exterior.

For example, whenever plaster is damaged around windows and you see damp wallpaper, the windows and roofing area above should be inspected. If you haven't found the source of moisture, don't repair!

Ongoing maintenance of the exterior is critical to deter the invaders. Repair deteriorated siding and damaged roofing materials, such as slate, tile, or wood shingles. Overall, keeping up with smaller projects is far preferable to replacing whole areas of historic material with new material. Not only will this be less expensive, your house will retain its authenticity for future generations to enjoy.

On another topic, if you let vines grow directly on brick or wood, they may look mellow, but, without a trellis to hold them away from the house, the roots erode mortar joints and foundations as they seek nourishing dampness within. Vines also hold moisture against exterior surfaces. Though almost everyone enjoys a bit of planned nature in the yard, when nature grows with abandon out of brick walls or cracks in the sidewalks, or on the roof, we should turn on it as the enemy!

Next, always keep gutters and downspouts in good repair. This is critical in order to convey moisture away from the house. Dry residue, such as pine needles from trees, can clog them, making rain water overflow onto the very historic materials you call "home."

  What to do--or not do.
The best advice is to use common sense maintenance approaches to keep rain and moisture from entering your house. Here are suggestions to keep the invaders under control.

Roofs, gutters & downspouts: Don't apply "tar goop" (asphaltic compounds) to try to make repairs because it doesn't work in the long run and can actually damage historic materials! Keep your roof weather-tight and functioning properly. Repair the flashing and cracked or broken downspouts. Inspect the roofing itself at least once a year, preferably in the spring.

Replace any missing or damaged roofing shingles, slates, or tiles.

 

Window and door openings: Eliminate any cracks or open joints.Caulk or repoint around openings or steps. Repair or re-set weatherstripping, then repaint, as necessary.

 

Walls: Don't ever apply a waterproof coating to an above-ground masonry wall--it can trap moisture underneath, causing further damage to the historic material. Repair damaged surface materials with care. Repoint masonry with appropriately formulated mortar. Prime and repaint wooden, metal, or masonry elements or surfaces.

 

Foliage: Keep all foliage and vines away from the house. Trim overhanging trees to keep the debris out of gutters and to prevent limbs from rubbing against building materials. Remove moisture-retaining elements, such as shrubbery, from foundations.

 

Moisture invasion from the ground "up."
Below-grade ground moisture can be a major problem. To do battle and win means you have to find an efficient way to handle surface rain run-off. The statistics would seem discouraging for those who care for a historic house. A heavy rain of 2" in an hour can produce 200 gallons of water from downspout discharge alone!

Now--if a downspout is clogged or broken, it can't carry water away from the house, which is its function. As a result, the ground around the foundation quickly becomes oversaturated. Moisture is absorbed by the foundation walls, making for a damp basement, and may cause the masonry and adjacent wooden structural elements of the house to deteriorate.

Another, more sinister, kind of invader is called "rising damp." Generally the result of high water tables or a constant source of dampness under the footings, you have probably seen a stain on masonry houses, often reaching 2 or 3 feet above the foundation. It really looks ugly. But don't try to apply some kind of waterproof coating to the wall. It only makes things worse! Improve the drainage, or, if that doesn't work, have a physical barrier, such as a slate course or plastic sheeting, professionally installed.

Sometimes further investigation is needed to get a dryer foundation. There may be underground wells, cisterns, abandoned pipes or other "hidden holders" of moisture. Tidal areas may have a history of chronic ground moisture, and there are seasonally high water tables to deal with as well. If regular maintenance procedures don't rid your house and yard of moisture problems, then more extensive remedial work will need to be done.

 

  What to do--or not do.
The best advice is to use common sense maintenance procedures to eliminate standing water and increase ventilation of the basement, or to correct existing high moisture levels, if necessary. Here are suggestions to keep the invaders under control.

 

 

 

 

 

Foundation and Yard: Eliminate low spots around building foundations. Clean out existing downspout boots twice a year or add an extension to leaders to carry moisture away from foundation. Do a hose test to verify that surface drains are functioning.

Reduce moisture used to clean steps and walks. Eliminate the use of chlorides to melt ice, which can cause damage to masonry. Check the operation of irrigation systems, hose bib leaks,and clearance of air conditioning "drip" drain outlets.

Consider installing a "French drain" to reduce splash-back onto foundation walls.

Or, a more expansive drainage system may be installed to direct water away from the house and into the yard.

Crawl space: Check the foundation grilles to be sure they provide enough ventilation; vents may need to be added if there are none.
Close grilles seasonally in winter, if they are not needed, or in summer, if hot humid air is getting into air conditioned spaces.

Basement: To reduce the amount of moisture,add a de-humidifier. If there are vents, increase air flow by installing a vent fan. To remedy a chronic moisture problem in the basement, such as a visibly wet floor or periodic ponding, install an electric sump pump (right). Then, once any mechanical device is in place, be sure to take care of it provide by providing routine maintenance.

Piping/ductwork: Check for condensation on pipes and insulate the pipes or seal the joints. Replace older pipes subject to leaking or overflowing.

 

 

 

Moisture Invasion from "within."
The most obvious problem you may encounter is from leaky plumbing pipes and mechanical equipment. Even new plumbing can leak, but older water and sewer pipes are particularly vulnerable.

As a result, slow leaks at plumbing joints hidden within walls and ceilings can stain ceiling plaster or wallpaper, ultimately rot floor boards, and even lead to decay of structural members! Maintaining and repairing, or, if necessary, replacing older plumbing and mechanical equipment are the most common solutions.

Next, condensation produced inside the house can create some real headaches! It's caused when moist warm vapor in the air cools on interior surfaces and changes into liquid. Usually settling on paint, the moist film can result in an unhealthy interior, heavy with mold and mildew spores.

What makes it worse is that the condensation invader is primarily occupant produced! Did you know that a house with four people in it can generate between 10 and 16 pounds of water a day (approximately 1 ½- 2 gallons) from normal, every day activities, such as showering, cooking, and doing laundry? Unvented gas stoves and kerosene heaters also give off a large amount of unwanted moisture. Bathrooms, kitchens, and laundry areas should all have vent fans that are turned on when the rooms are in active use.

When moisture appears as a film on interior window surfaces, it's a sign that you need to take defensive action. In cold climates, install storm windows. This reduces condensation and its damaging effects to historic materials, as well as your health.

In summary, reducing condensation through additional ventilation or installing storm windows can really help preserve your historic house!

 

 

  What to do--or not do.
The best advice is to use common sense maintenance procedures to reduce damage from interior moisture. Here are suggestions to keep the invaders under control with a focus on keeping equipment functioning; replacing broken components; and even installing additional equipment where moisture problems are evident.

Plumbing pipes: Consider use of a floor water sensor in the basement to let you know if you have a problem! Add insulation to plumbing or radiator pipes located in areas subject to condensation or freezing, such as along outside walls, in attics, or in unheated basements.
Replace older pipes that are subject to leaking or overflowing!

Mechanical equipment: Check condensation pans and drain lines to keep them clear at all times. Insulate and seal joints in exposed metal ductwork to avoid drawing in moist air.

Cleaning: Routinely dust and clean surfaces. Caulk around tile floor and wall connections and keep floor grout in good condition.

Ventilation:  Reduce household-produced moisture, if it's a problem, by increasing ventilation, especially in the basement.

 

Vent clothes dryers to the outside. Install and always useexhaust fans in bathrooms, showers, and kitchens. Control mold and mildew by adding a whole house fan for increased air flow throughout the house.

Interior climate control: Adjust the temperature and relative humidity to manage interior condensation.

Correct areas of improperly balanced pressure for HVAC systems that may be causing a moisture problem.

THE NEXT STEPS 
The moisture problems discussed in this article are common for historic homeowners and the stewards of historic buildings.  We provide qualified consultation and contracting services for adaptive re-use projects as green building practices are applied to repurposed structures for improved sustainability.  Contact Olde Mohawk to discuss options and solutions that will preserve the historic fabric of your structure and improve the quality of life for the occupants.

 

Content source:  National Park Service publication All Wet & How to Prevent It...Managing Moisture in Your Historic House, created by Kay Weeks with Sharon C. Park, FAIA, and Anne E. Grimmer in January 2000, using established treatment methodology from Preservation Briefs 39, but presenting an entirely new product for a web audience in a long distance learning format.