RCI Interface »» •» 19 PRESERVATION BRIEFS The Repair and Replacement of Historic Wooden Shingle Roofs Sharon C. Park, Al A Part II of II Reprint from: U.S. Department of the Interior, National Park Service, Preservation Assistance Division, Technical Preservation in this issue 19 Preservation Briefs, page 1 Disaster Response Team, page 10 CRC Exam Eligibilty, page 10 RCI Executive Committee Meets in Raleigh, page 10 News Hash!, page 11 1990/1991 Calendar, page 11 Replacing Deteriorated Roofs: Matching the Historic Appearance Historic wooden roofs using straight edgegrain heartwood shingles have been known to last over sixty years. Fifteen to thirty years, how¬ ever, is a more realistic lifespan for most premium modem wooden shingle roofs. Contributing factors to deterioration include thinness of the shingle, the durability of the wood species used, the exposure to the sun, the slope of the roof, the presence of lichens or moss growing on the shingle, poor ventilation levels under the shingle or in the roof, the presence of overhanging tree limbs, pollutants in the air, the original in¬ stallation method, and the history of the roof maintenance. Erosion of the softer wood within the growth rings is caused by rainwater, wind, grit, fungus and the breakdown of cells by ultraviolet rays in sunlight. If the shingles cannot adequately dry between rains, if moss and lichens are allowed to grow, or if debris is not removed from the roof, moisture will be held in the wood and accelerate deterioration. Moisture trapped under the shingle, condensation, or poorly ventilated attics will also ac¬ celerate deterioration. In addition to the eventual deterioration of wooden shingles, impact from falling branches and workmen walking on the roof can cause local¬ ized damage. If, however, over 20% of the shingles on any one surface appear eroded, cracked, cupped or split, or if there is evidence of per¬ vasive moisture damage in the attic, replacement should be considered. If only a few shingles are missing or damaged, selective replacement may be possible. For limited replacement, the old shingle is removed and a new shingle can be inserted and held in place with a thin metal tab, or “babbie.” This reduces disturbance to the sound shingles above. In in¬ stances where a few shingles have been cracked or the joint of overlap¬ ping shingles is aligned and thus forms a passage for water penetration, a metal flashing piece slipped under the shingle can stop moisture tem¬ porarily. If moisture is getting into the attic, repairs must be made quick¬ ly to prevent deterioration of the roof structural framing members. When damage is extensive, replacement of the shingles will be neces¬ sary, but the historic sheathing or shingle lath under the shingles may be in satisfactory condition. Often, the historic sheathing or shingle laths, by their size, placement, location of early nail holes, and water stain marks, can give important information regarding the early shingles used. Before specifying a replacement roof, it is important to establish the original shingle material, configuration, detailing and installation (see illus. 11). If the historic shingles are still in place, it is best to remove several to determine the size, shape, exposure length, and special fea- Newsletter of The Roof Consultants Institute 2 11. The replacement sawn red cedar shingles matched the deteriorated shingles exactly for this bam re-roofing. The old shingles, seen to the far left, were removed as the new shingles were installed. Even the horizontal coursing matched because the exposure length for both old and new shingles was the same. Photo: Williamsport Preservation Training Center. tures from the unweathered portions. If there are already replacement shingles on the roof, it may be necessary to verify through photographic or other research whether the shingles currently on the roof were an ac¬ curate replacement of the historic shingles. The following information is needed in order to develop accurate specifications for a replacement shingle: Original wood type (White Oak, Cypress, Eastern White Pine, Western, Red Cedar, etc.) Size of shingle (length, width, butt thickness, taper) Exposure length and nailing pattern (amount of exposure, place¬ ment and type of nails) Type of fabrication (sawn, handsplit, dressed, beveled, etc.) Distinctive details (hips, ridges, valleys, dormers, etc.) Decorative elements (trimmed butts, variety of pattern, applied color coatings, exposed nails) Type of substrate (open shingle lath or sheathing, closed sheathing, insulated attics, sleepers, etc.) Replacement roofs must comply with local codes which may require, for example, the use of shingles treated with chemicals or pressure-im¬ pregnated salts to retard fire. These requirements can usually be met without long-term visual effects on the appearance of the replacement roof. The accurate duplication of a wooden shingle roof will help ensure the preservation of the building’s architectural integrity. Unfortunately, the choice of an inappropriate shingle or poor installation can severely Newsletter of The Roof Consultants Institute 3 12. Inappropriately selected and installed wooden shingles can drastically alter the historic character of a building. Photo: National Park Service. detract from the building’s historic appearance (see illus. 12). There are a number of commercially available wooden roofing products as well as custom roofers who can supply specially-made shingles for historic preservation projects (see Shingle and Shake Chart, illus. 13). Unless res¬ toration or reconstruction is being undertaken, shingles that match the visual appearance of the historic roof without repheating every aspect of the original shingles will normally suffice. For example, if the historic wood species is no longer readily available, Western Red Cedar or East¬ ern White Pine may be acceptable. Or, if the shingles are located high on a roof, sawn shingles or commercially available shakes with the rustic faces factory-sawn off may adequately reproduce the appearance of an historic handsplit and dressed shingle. There will always be certain features, however, that are so critical to the building’s character that they should be accurately reproduced. Fol¬ lowing is guidance on matching the most important visual elements. • best quality wood with a similar surface texture • matching size and shape: thickness, width, length • matching installation pattern: exposure length, overlaps, hips, ridges, valleys, etc. • matching decorative features: fancy butts, color, exposed nails Highest Priority in Replacement Shingles Newsletter of The Roof Consultants Institute 4 AVAILABLE WOODEN SHINGLES AND SHAKES FOR RE-ROOFING TYPE SIZE DESCRIPTION NOTES Custom split & dressed Made to match historic shingles Handsplit the traditional way with froe & mallet. Tapered. Surfaces dressed for smoothness Appropriate if: • Worked to match uniformly dressed original shingles Tapersplit* Typically: L = 15″, 18″, 24″ W = 4″-14″ Butts vary 1/2″ -3/4″ Commercially available. Handsplit the traditional way with froe & mallet. Tapered. Bundles contain varying widths & butt thicknesses. Surfaces may be irregular along grain. Appropriate if: • irregular surfaces are dressed • butt thicknesses ordered uniform • wide shingles are split Straightsplit Typically: L»15″, 18″, 24″ W = 4″-14″ Butts vary mediums = 3/8—3/4″ heavies ■ 3/4-1V4″ Commercially available. Hand or machine split without taper. Bundles contain varying butt thicknesses; often very wide shingles. Surface may be irregular along the grain. Thick shingles not historic. Nof appropriate for most preservation projects • Limited use of thin, even straightsplits on some cabins, bams, etc. Handsplit* resawn Typically: L-15″, 18″, 24″ W»4″-14″ Butts vary mediums = 3/8-3Z4″ heavies = 3/4-1V4″ Commercially available. Machine split and sawn on the backs to taper. Split faces often irregular, even corrugated in appearance. Butt thickness vary and may be too wide. Nof appropriate for preservation projects Tapersawn* Typically: L=15″, 18″, 24″ W»4″-14″ Butts vary l/2″-3/4″ Commercially available. Made from split products with sawn surfaces. Tapered. Butt thicknesses vary and shingles may be too wide. Saw marks may be pronounced. Appropriate if: • butt thicknesses ordered uniform • wide shingles are split • pronounced saw marks sanded Sawnstraight butt Typically: L = 16″-.40(<3/8″) 18″-. 45 24″-. 50 (1/2″) W ® Varies by order Custom or commercially available. Tapered. Sawn by circular saw. Appropriate to reproduce historic sawn shingles Sawnfancy I J butt \/ L> Typically: L»16″-.40(<3/8″) 18″-. 45 24″-.50 (1/2″) W « Varies by order Custom or commercially available. Tapered. Sawn by circular saw. A variety of fancy butts available Appropriate to reproduce historic fancy butts Steam-bent // r ‘ Varies by order to match, “Thatch” roofs Custom or commercially available. Tapered. Thin sawn shingles are steamed and bent into rounded forms. Appropriate to reproduce “thatch” shingles 13. This chart identifies a variety of shingles and shakes used for reroofing buildings. The identifies product names used by the Red Cedar Shingle and Handsplit Shake Bureau, although shingles and shakes of the types described are available in other woods. Manufacturers define “Shakes” as split products while “shingles” refer to sawn products. Shingle, however, is the historic term used to describe wooden roofing products, regardless of how they were made. Whether shingles or shakes are specified for re-roofing, they should match the size and appearance of the historic shingles. Chart: Sharon C. Park; delineation by Kaye Ellen Simonson. Newsletter of The Roof Consultants Institute 5 • species of wood • method of fabrication of shingle, if visual appearance matches • use of fire-retardants, or preservative treatments, if visual im¬ pact is minimal • use of modem flashing, if sensitively installed • use of small sleepers for ventilation, if visual impact is minimal and rake boards are sensitively treated • method of nailing, if the visual pattern matches Areas of Acceptable Differences • highly textured wood surfaces and irregular butt ends, unless documented • standardized details (prefab hips, ridges, panels, etc.) unless documented • too wide shingles or those with flat grain (which may curl), un¬ less documented Types of Wood: Western Red Cedar, Eastern White Pine, and White Oak are most readily available today. For custom orders, cypress, red oak, and a number of other historically used woods may still be avail¬ able. Some experiments using non-traditional woods (such as yellow pine and hemlock) treated with preservative chemicals are being tested for the new construction market, but are generally too thick, curl too easily, or have too pronounced a grain for use on historic buildings. Method of manufacture: Commercially available modem shingles and shakes are for the most part machine-made. While commercially available shakes are promoted by the industry as handsplit, most are split by machine (this reduces the high cost of hand labor). True handsplit shingles, made the traditional way with a froe and mallet, are substantial¬ ly more expensive, but are more authentic in appearance than the rough, highly textured machine-split shakes. An experienced shingler can con¬ trol the thickness of the handsplit shingle and keep the shingle surface grain relatively even. To have an even roof installation, it is important to have handsplit shingles of uniform taper and to have less than l/8th variation across the surface of the shingle. For that reason, it is important to dress the shingles or to specify uniform butt thickness, taper, and sur¬ faces. Commercially available shakes are shipped with a range of butt sizes within a bundle (e.g., 1/2″, 5/8″, 3/4″ as a mix) unless otherwise specified. Commercially available shakes with the irregular surfaces sawn off are also available. In many cases, except for the residual cir¬ cular saw marks, these products appear not unlike a dressed handsplit shingle. Treatments and Materials to Avoid What is Currently Available Newsletter of The Roof Consultants Institute 4 AVAILABLE WOODEN SHINGLES AND SHAKES FOR RE-ROOFING TYPE SIZE DESCRIPTION NOTES Custom split & dressed Made to match historic shingles Handsplit the traditional way with froe & mallet. Tapered. Surfaces dressed for smoothness Appropriate if: • Worked to match uniformly dressed original shingles Tapersplit* Typically: L-15″, 18″, 24″ W = 4″-14″ Butts vary 1/2″ -3/4″ Commercially available. Handsplit the traditional way with froe & mallet. Tapered. Bundles contain varying widths & butt thicknesses. Surfaces may be irregular along grain. Appropriate if: ♦ irregular surfaces are dressed • butt thicknesses ordered uniform • wide shingles are split Straightsplit Typically: L-15″, 18″, 24″ W»4″-14″ Butts vary mediums = 3/8-3Z4″ heavies -3/4-V/4″ Commercially available. Hand or machine split without taper. Bundles contain varying butt thicknesses; often very wide shingles. Surface may be irregular along the grain. Thick shingles not historic. Not appropriate for most preservation projects • Limited use of thin, even straightsplits on some cabins, bams, etc. Handsplit* ”””’ resawn Typically: L-15″, 18″, 24″ W»4″-14″ Butts vary mediums = 3/8—3/4″ heavies = 3/4-1V4* Commercially available. Machine split and sawn on the backs to taper. Split faces often irregular, even corrugated in appearance. Butt thickness vary and may be too wide. Not appropriate for preservation projects Tapersawn* Typically: L-15″, 18″, 24″ W-4″-14″ Butts vary 1/2″ -3/4″ Commercially available. Made from split products with sawn surfaces. Tapered. Butt thicknesses vary and shingles may be too wide. Saw marks may be pronounced. Appropriate if: • butt thicknesses ordered uniform • wide shingles are split • pronounced saw marks sanded Sawnstraight butt Typically: L = 16″-. 40 (<3/8″) 18″-.45 24″ -.50 (1/2″) W – Varies by order Custom or commercially available. Tapered. Sawn by circular saw. Appropriate to reproduce historic sawn shingles Sawnfancy I J butt \/ 1> Typically: L- 16″-. 40 (<3/8″) 18″-. 45 24″-. 50 (1/2″) W – Varies by order Custom or commercially available. Tapered. Sawn by circular saw. A variety of fancy butts available Appropriate to reproduce historic fancy butts Steam-bent // / Varies by order to match, “Thatch” roofs Custom or commercially available. Tapered. Thin sawn shingles are steamed and bent into rounded forms. Appropriate to reproduce “thatch” shingles 13. This chart identifies a variety of shingles and shakes used for reroofing buildings. The identifies product names used by the Red Cedar Shingle and Handsplit Shake Bureau, although shingles and shakes of the types described are available in other woods. Manufacturers define “Shakes” as split products while “shingles” refer to sawn products. Shingle, however, is the historic term used to describe wooden roofing products, regardless of how they were made. Whether shingles or shakes are specified for re-roofing, they should match the size and appearance of the historic shingles. Chart: Sharon C. Park; delineation by Kaye Ellen Simonson. Newsletter of The Roof Consultants Institute 5 • species of wood • method of fabrication of shingle, if visual appearance matches • use of fire-retardants, or preservative treatments, if visual im¬ pact is minimal • use of modem flashing, if sensitively installed • use of small sleepers for ventilation, if visual impact is minimal and rake boards are sensitively treated • method of nailing, if the visual pattern matches • highly textured wood surfaces and irregular butt ends, unless documented • standardized details (prefab hips, ridges, panels, etc.) unless documented • too wide shingles or those with flat grain (which may curl), un¬ less documented Types of Wood: Western Red Cedar, Eastern White Pine, and White Oak are most readily available today. For custom orders, cypress, red oak, and a number of other historically used woods may still be avail¬ able. Some experiments using non-traditional woods (such as yellow pine and hemlock) treated with preservative chemicals are being tested for the new construction market, but are generally too thick, curl too easily, or have too pronounced a grain for use on historic buildings. Method of manufacture: Commercially available modem shingles and shakes are for the most part machine-made. While commercially available shakes are promoted by the industry as handsplit, most are split by machine (this reduces the high cost of hand labor). True handsplit shingles, made the traditional way with a froe and mallet, are substantial¬ ly more expensive, but are more authentic in appearance than the rough, highly textured machine-split shakes. An experienced shingler can con¬ trol the thickness of the handsplit shingle and keep the shingle surface grain relatively even. To have an even roof installation, it is important to have handsplit shingles of uniform taper and to have less than l/8th variation across the surface of the shingle. For that reason, it is important to dress the shingles or to specify uniform butt thickness, taper, and sur¬ faces. Commercially available shakes are shipped with a range of butt sizes within a bundle (e.g., 1/2″, 5/8″, 3/4″ as a mix) unless otherwise specified. Commercially available shakes with the irregular surfaces sawn off are also available. In many cases, except for the residual cir¬ cular saw marks, these products appear not unlike a dressed handsplit shingle. Areas of Acceptable Differences Treatments and Materials to Avoid What is Currently Available Newsletter of The Roof Consultants Institute 6 Sawn shingles are still made much the same way as they were histori¬ cally—using a circular saw. The circular saw marks are usually evident on the surface of most sawn shingles. There are a number of grooved, striated, or steamed shingles of the type used in the 20th century to effect a rustic or thatched appearance. Custom sawn shingles with fancy butts or of a specified thickness are still available through mill shops. In fact, shingles can be fabricated to the weathered thickness in order to be in¬ tegrated into an existing historic roof. If sawn shingles are being used as a substitute for dressed handsplit shingles, it may be desirable to belt sand the surface of the sawn shingles to reduce the prominence of the cir¬ cular saw marks. As seen from the Shingle and Shake chart, few of the commercially available shakes can be used without some modification or careful specification. Some, such as heavy shakes with a corrugated face, should be avoided altogether. While length, width, and butt configuration can be specified, it is more difficult to ensure that the thickness and the tex¬ ture will be correct. For that reason, whatever shingle or shake is desired, it is important to view samples, preferable an entire bundle, before specifying or ordering. If shingles are to be trimmed at the site for special conditions, such as fanned hips or swept valleys, additional shingles should be ordered. Coatings and Treatments: Shingles are treated to obtain a fire-retar¬ dant rating; to add a fungicide preservative (generally toxic); to revital¬ ize the wood with a penetrating stain (oil as well as water-based); and to give color. While shingles can be left untreated, local codes may require that only fire-retardant shingles be used. In those circumstances, there are several methods of obtaining rated shingles (generally class “B” or “C”). The most effective and longest-lasting treatment is to have treated salts pressure-impregnated into the wood cells after the shingles have been cut. Another method (which must be periodically renewed) is to apply chemicals to the surface of the shingles. If treated shingles need trim¬ ming at the site, it is important to check with the manufacturer to ensure that the fire-retardant qualities will not be lost. Pressure-impregnated shingles, however, may usually be trimmed without loss of fire-retardant properties. The life of a shingle roof can be drastically shortened if moss, lichens, fungi or bacterial spores grow on the wood. Fungicides (such as chromated copper arsenate, CCA) have been found to be effective in in¬ hibiting such fungal growth, but most are toxic. Red cedar has a natural fungicide in the wood cells and unless the shingles are used in unusually warm, moist environments, or where certain strains of spores are found, I an applied fungicide is usually not needed. For most woods, the Forest Newsletter of The Roof Consultants Institute 7 Products Laboratory of the U.S. Department of Agriculture has found that fungicides do extend the life of the shingles by inhibiting growth on or in the wood. There are a variety available. Care should be taken in ap¬ plying these chemicals and meeting local code requirements for proper handling. Penetrating stains and water-repellent sealers are sometimes recom¬ mended to revitalize wood shingles subject to damage by ultraviolet rays. Some treatments are oil-bome, some are water-borne, and some are combined with a fungicide or a water repellent. If any of these treat¬ ments is to be used, they should be identified as part of the specifica¬ tions. Manufacturers should be consulted regarding the toxicity or other potential complications arising from the use of a product or of several in combination. It is also important not to coat the shingles with vapor-im¬ permeable solutions that will trap moisture within the shingle and cause rotting from beneath. Specifications and roofing details should be developed for each project. Standard specifications may be used as a basic format, but they should be modified to reflect the conditions of each job. Custom shingles can still be ordered that accurately replicate a historic roof, and if the roof is simple, an experienced shingler could install it without com¬ plicated instructions. Most rehabilitation projects will involve competi¬ tive bidding, and each contractor should be given very specific information as to what type of shingles are required and what the instal¬ lation details should be. For that reason, both written specifications and detailed drawings should be part of the construction documents. For particularly complex jobs, it may be appropriate to indicate that only roofing contractors with experience in historic preservation projects be considered (see illus. 14). By pre-qualifying the bidders, there is greater assurance that a proper job will be done. For smaller jobs, it is al¬ ways recommended that the owner or architect find a roofing contractor who has recently completed a similar project and that the roofers are similarly experienced. Specifications identify exactly what is to be received from the sup¬ plier, including the wooden shingles, nails, flashings, and applied coat¬ ings. The specifications also include instructions on removing the old roofing (sometimes two or more earlier roofs), and on preparing the sur¬ face for new shingles, such as repairing damage to the lath or sheathing boards. If there are to be modifications to a standard product, such as cut¬ ting beveled butts, planing off residual surface circular saw marks, or controlling the mixture of acceptable widths (3″-8″), these too should be specified. Every instruction for modifying the shingles themselves should be written into the specifications or they may be overlooked. Specifications for the Replacement Roof Newsletter of The Roof Consultants Institute 8 Replacement Roofing for Appomattox Manor: City Point Unit of Petersburg National Battlefield, Hopewell, Virginia A. The later non-historic shingles were removed from Appomattox Manor (circa 1840 with later addi¬ tions) and roofing paper was installed for temporary protection during the re-shingling. B. The original 19th century shingles were handsplit, 18″ long, 5/8″ thick, 3″-4″ wide with curved butts and painted red. These appear on the roof of a dormer that was covered by a later remodeling that extended the original roof. These shingles were used as the basis for the replacement shingles. Photo: John Ingle. Type of wood to be used: Western Red Cedar Grade of wood and manufacturing process: Number One, Tapersplit Shakes, 100% clear, 100% edgegrain, 100% heartwood, no excessive grain sweeps, curvatures not to exceed 1/2″ from level plain in length of shake; off grade (7% tolerance) material must not be used. 14. Original 19th-century handsplit and dressed wooden shingles 18″ long, 3″-4″ side, and 5/8″ thick were found in place on the Appomattox Manor at Hopewell, Virginia. The butts were curved and evidence of a red stain remained. The specifications and details were researched so that the appearance of the historic shingles and installation patterns could be matched in the re-shingling project. Photo: John Ingle. Excerpts from Specifications Newsletter of The Roof Consultants Institute 9 Size of the shingle: 18″ long, 5/8″ butt tapered to 1/4″ head, 3″-4″ wide, sawn curved butts, 5 1/2″ exposure Type of nails and flashing: double hot dipped galvanized nails sized to penetrate sheathing totally; metal flashing to be 20 oz. lead-coated copper, or terne-coated stainless steel; additional flashing reinforcement to be aluminum foil type with fiber backing to use at hips, ridges, eaves, and valleys. Type of sheathing: uninsulated attic, any deteriorated 3/4″ sheathing boards, spaced l/2″-3/4″, to be replaced in kind. C. The replacement shingles (see specifications), matched the historic shingles and were of such high quality that little hand dressing was needed at the site. The building paper, a temporary protection, D. The fanned hips, swept valleys, (shown here) and projecting ridge combs were installed as part of the re-roofing project. Special features, when documented, should be reproduced when re-shingling historic roofs. continued on page 12 Newsletter of The Roof Consultants Institute 10 DISASTER RESPONSE TEAM PROCEDURES AND GUIDELINES FOR CRC EXAM ELIGIBILITY RCI Executive Committee Meets at RCI RCI’s Disaster Response Program is underway. This program is designed to provide pre-disaster and post-disaster standardized data on roof systems in areas from Brownsville TX to Dover DE. This program can successfully contribute valuable, real world roof performance data and be instrumental in the reduction of roof-related losses as a result of windstorm. Roof Evaluation Forms were sent out recently to those RCI members who expressed a desire to participate. To find out more about this volunteer program, please contact Allan Kidd, Canon Consulting & Engineering, P.O. Box 17007, Spartanburg, SC 29301 (803-574-6500) or RCI Headquarters. A PRESS RELEASE ON RCI’S DISASTER RESPONSE PRO¬ GRAM IS BEING DEVELOPED. PLEASE CALL OR WRITE RCI HEADQUARTERS TO GIVE THE NAME, ADDRESS, AND EDITOR FOR YOUR LOCAL NEWSPAPER(S). The following procedures and guidelines apply to those RCI Profes¬ sional and/or Industry members in good standing who desire to take the RCI Certified Roof Consultant Examination. The CRC Exam is offered twice a year: (1) “Spring Exam” in conjunction with RCI National Con¬ vention and (2) “Autumn Exam.” Those Taking CRC Exam for First Time: Must submit FULLY completed CRC “Education and Experience” ap¬ plication form to RCI Headquarters 150 days in advance of examination date. Those Who Took and Failed the CRC Exam for the First Time in March 1990: Must FULLY complete requirements of CRC “Education and Ex¬ perience” application and submit to RCI Headquarters 150 days in ad¬ vance of examination date. Those Who Failed the Exam Prior to March 1990: Must submit to RCI Headquarters letter requesting permission to retake the exam 120 days prior to examination date. Applicants will receive written authorization to take the exam ap¬ proximately 6 weeks prior to the exam date. The RCI Executive Committee met at RCI Headquarters in Raleigh, North Carolina, on Saturday, October 6, 1990. The eight-hour meeting with RCI staff afforded committee members the opportunity to better un¬ derstand headquarter operations and the opportunity to discuss and coor¬ dinate the undertaking of new member programs. Newsletter of The Roof Consultants Institute 11 NEWS FLASH DATELINE: RALEIGH NC NOVEMBER 1, 1990 RCI is pleased to announce that Past President, George F. Kanz, PE, CRC has just finished negotiating with NRCA for booth space at NRCA’s national trade show in Orlando, Florida, February 5-8, 1991. NRCA will also have a booth at the RCI Sixth National Convention in Colorado Springs, April 28 – May 1, 1991. This is a great opportunity to expose the attributes of the Roof Con¬ sultants Institute and its membership to the professional attendees at the NRCA show. The RCI Convention Committee will be coordinating booth activities, contents, etc. We welcome any and all suggestions and will desperately need volunteers to help man our booth at the NRCA convention. Please contact Barry S. Krum, at 1-800-258-6500, with any words of wisdom or commitment for time. Barry S. Krum Industry Member RCI Convention Committee 1990/1991 RCI CALENDAR OF EVENTS SPRTTECH90 December 6, 1990 Dallas, TX Call RCI Headquarters to purchase tickets at a savings! RCI CONVENTION April 28 – May 1, 1991 Colorado Springs, CO RIEI/RCI SEMINAR May 13-16, 1991 Raleigh, NC REGION n January 15, 1991 Orlando, FL REGION BI January 25, 1991 NRCA Headquarters REGION VI February 11, 1991 Las Vegas, NV June 10, 1991 San Francisco August 12, 1991 Phoenix, AZ November 11, 1991 Los Angeles, CA Olympic Manufacturing Group, Inc. offers a full line of roof fastening systems and accessories for both built up and single ply roofing ap¬ plications. In addition, Olympic is the national marketing agent for the Roofcap Paver, an insulating ballast and roof paver system. Our products, as well as our field technical service, are available worldwide. Olympic is the number one fastener manufacturer in the United States and the renown expert on the total securement of roofing applications. Olympic Manufacturing Group Sponsors Interface Issue Newsletter of The Roof Consultants Institute 12 continued from page 9 Roofing Practices to Avoid The specifications and drawn details should describe special features important to the roof. Swept valleys, combed ridges, or wedged dormer cheek run-offs should each be detailed not only with the patterning of the shingles, but also with the placement of flashing or other unseen rein¬ forcements. There are some modem products that appear to be useful. For example, paper-coated and reinforced metal-laminated flashing is easy to use and, in combination with other flashing, gives added protec¬ tion over eaves and other vulnerable areas; adhesives give a stronger at¬ tachment at projecting roofing combs that could blow away in heavy wind storms. Clear or light-colored sealants may be less obvious than dark mastic often used in conjunction with flashing or repairs. These modem treatments should not be overlooked if they can prolong the life of the roof without changing its appearance. Certain common roofing practices for modem installations should be avoided in re-roofing a historic building unless specifically approved in advance by the architect. These practices interfere with the proper drying of the shingles or result in a sloppy installation that will accelerate deterioration (see illus. 15). They include improper coverage and spac¬ ing of shingles, use of staples to hold shingles, inadequate ventilation, particularly for heavily insulated attics, use of heavy building felts as an underlayment, improper application of surface coatings, causing stress in the wood surfaces, and use of inferior flashing that will fail while the shingles are still in good condition. Avoid skimpy shingle coverage and heavy building papers. It has become a common modem practice to lay impregnated roofing felts under new wooden shingle roofs. The practice is especially prevalent in roofs that do not achieve a full triple layering of shingles. Historically, approximately one third of each shingle was exposed, thus making a three-ply or three-layered roof. This assured adequate coverage. Due to the expense of wooden shingles today, some roofer expose more of the shingle if the pitch of the roof allows, and compensate for less than three layers of shingles by using building felts interwoven at the top of each row of shingles. This absorptive material can hold moisture on the under¬ side of the shingles and accelerate deterioration. If a shingle roof has proper coverage and proper flashing, such felts are unnecessary as a general rule. However, the selective use of such felts or other reinforce¬ ments at ridges, hips and valleys does appear to be beneficial. Beware of heavily insulated attic rafters. Historically, the longest lasting shingle roofs were generally the ones with the best roof ventila¬ tion. Roofs with shingling set directly on sold sheathing and where there is insulation packed tightly between the wooden rafters without ade- Newsletter of The Roof Consultants Institute 13 quate ventilation run the risk of condensation-related moisture damage to wooden roofing components. This is particularly true for air-condi¬ tioned structures. For that reason, if insulation must be used, it is best to provide ventilation channels between the rafters and the roof decking, to avoid heavy felt building papers, to consider the use of vapor barriers, and perhaps to raise the shingles slightly by using “sleepers” over the roof deck. This practice was popular in the 1920s in what the industry called a “Hollywood” installation, and examples of roofs lasting 60 years are partly due to this under-shingle ventilation. 15. These commercially available roofing products with rustic-split faces are not appropriate for his¬ toric preservation projects. In addition to the inaccurate appearance, the irregular surfaces and often wide spaces between shingles will allow wind-driven moisture to penetrate up and under them. The excessively wide boards will tend to cup, curl, and crack. Moss, lichens and debris will have a tenden¬ cy to collect on these irregular surfaces, further deteriorating the roofing. Photo: Sharon C. Park. Avoid staples and inferior flashing. The common practice of using pneumatic staple guns to affix shingles can result in shooting staples through the shingles, in crushing the wood fibers, or in cracking the shingle. Instead, corrosion-resistant nails, generally with barked or deformed shanks long enough to extend about 3/4″ into the roof deckng, should be specified. Many good roofers have found that the pneumatic nail guns, fitted with the proper nails and set at the correct pressure with the nails just at the shingle surface, have worked well and reduced the stress on shingles from missed hammer blows. If red cedar is used, cop¬ er nails should not be specified because a chemical reaction between the wood and the copper will reduce the life of the roof. Hot-dipped, zinccoated, aluminum, or stainless steel nails should be used. In addition, copper flashing and gutters generally should not be used with red cedar shingles as staining will occur, although there are some historic exmples Newsletter of The Roof Consultants Institute 14 where very heavy gauge copper was used which outlasted the roof shingles. Heavier weight flashing (20 oz.) holds up better than lighter flashing, which may deteriorate faster than the shingles. Some metals may react with salts or chemicals used to treat the shingles. This should be kept in mind when writing specifications. Terne-coated stainless steel and lead-coated copper are generally the top of the line if copper is not appropriate. Avoid patching deteriorated roof lath or sheathing with plywood or composite materials. Full size lumber may have to be custom-or¬ dered to match the size and configuration of the original sheathing in order to provide an even surface for the new shingles. It is best to avoid plywood or other modem composition boards that may deteriorate or delaminate in the future if there is undetected moisture or leakage. If large quantities of shingle lath or sheathing must be removed and replaced, the work should be done in sections to avoid possible shifting or collapse of the roof structure. Maintenance Avoid spray painting raw shingles on a roof after installation. Rapidly drying solvent in the paint will tend to warp the exposed surface of the shingles. Instead, it is best to dip new shingles prior to installation to keep all of the wood fibers in the same tension. Once the entire shingle has been treated, however, later coats can be limited to the ex¬ posed surface. The purpose of regular or routine maintenance is to extend the life of the roof. The roof must be kept clean and inspected for damage both to the shingles and to the flashing, sheathing, and gutters. If the roof is to be walked on, rnbber soled shoes should be worn. If there is a simple ridge, a ladder can be hooked over the roof ridge to support and dis¬ tribute the weight of the inspector. Keeping the roof free of debris is important. This may involve only sweeping off pine needles, leaves and branches as needed. It may in¬ volve trimming overhanging branches. Other aspects of maintenance, such as removal of moss and lichen build-up, are more difficult. While they may impart a certain charm to roofs, these moisture-trapping or¬ ganisms will rot the shingles and shorten the life of the roof. Buildups may need scraping and the residue removed with diluted bleaching solu¬ tions (chlorine), although caution should be used for surrounding materials and plants. Some roofers recommend power washing the roofs periodically to remove the dead wood cells and accumulated debris. While this makes the roof look relatively new, it can put a lot of water under shingles, and the high pressure may crack or otherwise damage them. The added water may also leach out applied coatings. Newsletter of The Roof Consultants Institute 15 If the roof has been treated with a fungicide, stain, or revitalizing oil, it will need to be re-coated every few years (usually every 4-5). The manufacturer should be consulted as to the effective life of the coating. With the expense associated with installation of wood shingles, it is best to extend the life of the roof as long as possible. One practical method is to order enough shingles in the beginning to use for periodic repairs. Periodic maintenance inspections of the roof may reveal loose or damaged shingles that can be selectively replaced before serious mois¬ ture damage occurs (see illus. 16). Keeping the wooden shingles in good condition and repairing the roof, flashing and guttering, as needed, can add years of life to the roof. A combination of careful research to determine the historic ap¬ pearance of the roof, good specifications, and installation details designed to match the historic roof, and long-term maintenance, will make it possible to have not only a historically authentic roof, but a costeffective one. It is important that professionals be part of the team from the beginning. A preservation architect should specify materials and con¬ struction techniques that will best preserve the roofs’s historic ap¬ pearance. The shingle supplier must ensure that the best product is delivered and must stand behind the guarantee if the shipment is not cor¬ rect. The roofer must be knowledgeable about traditional craft practices. Once the new shingle roof is in place, it must be properly maintained to give years of service. 16. Routine maintenance is necessary to extend the life of the roof. On this roof, the shingles have not seriously eroded, but the presence of lichens and moss is becoming evident and there is a few cracked and missing shingles. The moss spores should be removed, missing shingles replaced, and small pieces of metal flashing slipped under cracked shingles to keep moisture from penetrating. Photo: Williamsport Preservation Training Center. Conclusion Newsletter of The Roof Consultants Institute 16 Acknowledgements The author gratefully acknowledges the invaluable assistance of co¬ worker Michael Auer in preparing this brief for publication. In addition, the following individuals are to be thanked for this contribution to this manuscript: Reed Engle, Historical Architect, NPS; John Ingle, Histori¬ cal Architect, NPS; Martin Obando, Eastern District Manager, Red Cedar Shingle & Handsplit Shake Bureau; and Peter Sandbeck, North Carolina Division of Archives and History. Appreciation is extended to: the staff of Technical Preservation Services Branch and NPS regional of¬ fices; Michael Lynch of the Office of Parks, Recreation and Historic Preservation in Albany, New York; and to Penelope H. Batcheler and William Brookover, Historical Architects, Independence National His¬ toric Park, for their review of this manuscript and constructive com¬ ments. Special thanks are given to Kaye Ellen Simonson for the illustrations in the charts. TO ORDER PRESERVATION BRIEF #19, Repair and Replacement of Historic Wooden Shingle Roofs (Stock # 024-005-01053-0) and/or PRESERVATION BRIEF #4, Roofing for Historic Buildings, (Stock # 024-005-00880-2) send $1.00/copy to: Superintendent of Documents, Government Printing Office, Washington, DC 20402-9325. Further Reading Bucher, Robert C. “The Long Shingle.” Pennsylvania Folklife. Vol. XVI11, No. 4, Summer 1969. Cox, Richard E. “Wooden Shingles from the Fortress of Louisbourg.” Bulletin of the Association for Preservation Technology. Vol. II, Nos. 1-2 1970 p.p. 65. Engle, Reed. “Restoring a Roofing.” CRM Bulletin, a publication of the National Park Service, Vol. 8, No. 6 Dec. 1985. Kidder, F.E. Building Construction and Superintendence, part II. New York: Wil¬ liam T. Comstock, 1902. LeVan, Susan. “Fire-Retardant Treatments for Wood Shingles.” Techline. Madison, Wisconsin: U.S.D.A. Forest Service, 1988. RC1 OFFICERS James E. Magowan CRC, President Donald E. Bush Sr CRC, First Vice-President Richard M. Horowitz, AIA, FRCl, Second Vice-President Joe F. Hale, Secretary Sam W Huff, CRC, Treasurer CHAIRMAN, RCI PUBLICATIONS COMMITTEE George A. Beck RCI STAFF Paula J. Baker, Executive Manager Sheila S. Shears, Administrative Assistant The “Interface Newsletter” is published by the Roof Consultants Institute. Copyright © 1988 Roof Consultants Institute. All rights reserved. Please address all submittals, subscription requests, advertising, etc. to the Roof Consultants Institute, 7424 Chapel Hill Road, Raleigh, NC 27607. Telephone 919/859-0742. The RCI logo, the name “Interface Newsletter” and the title “RCI Certified Roof Consultant” abbreviated “CRC” are the property of the Roof Consultants Institute and must not be used without permission. Disclaimer: The articles contained in this publication have been prepared for, and are intended to provide information that may be useful to members of the Roof Consultants Institute. RCI does not necessarily warrant this information. The reader must evaluate this information in light of the unique circumstances of any particular situation and must determine independently the applicability of this information thereto. Advertising in RCI publications does not constitute endorsement of any product or system by RCI or any of its roof consultant members. Newsletter of The Roof Consultants Institute
