EC 1271 750 Revised September 1993 Care and maintenance "^ of wood shingle and shake roofs S. S. Niemiec and T. D. Brown

A wooden shingle or shake roof or shake roof can provide an effective product used, the desired pattern or once represented one of the few types cover for your home or business appearance, the slope of the roof, and available. Today it is a premium establishment. the applicationDATE. procedures. These product that costs the home owner Most wood shingle and shake roofs variables also establish the quality of more to purchase and install than the are made from western redcedar the roof. more common asphalt shingle or (Thuja plicata) because of its excep- OFRoof quality, the site and the type rolled roofing product. Architects and tional properties, including defect-free of exposure to the weathering ele- building contractors choose wood straight grain, dimensional stability, ments, and the maintenance proce- roofs for their beauty and natural low weight (low density), impenetra- dures all serve to determine the appearance that blends well with the bility to fluids, and—probably most longevity of the roof. Simply stated, surrounding environment and en- important—decay resistance,OUT derived thicker, better roofs that are properly hances the structure's landscaping. from natural substances found within maintained under moderate exposure Additionally, wood shingles and the wood. conditions will last longer than shakes can provide superior perfor- Other wood species,IS notably thinner, lower-grade roofs exposed to mance in areas that experience high redwood (Sequoia sempervirens) and harsh conditions, without any care. winds or damage from hail. Although cypress (Taxodium distichum), have It's difficult, therefore, to predict they do have certain limitations similar properties and are sometimes how long any given roof will last. (susceptibility to rotting, splitting, and used; but decreasing supplies signifi- According to the U.S. Forest Products warping), proper maintenance and cantly restrict production and distribu- Laboratory, "...a good wood shingle care can minimize these limitations. tion. In addition, there's limited roof will last up to thirty years under A standard asphalt three-tab roof distribution of information:other woods that have favorable conditions" (see USDA generally requires little maintenance been impregnated with preservative Handbook 481). Care and mainte- during the time it's on the roof except chemicals either by pressure-treating nance are the keys: The better care for moss control. Asphalt-based roof (best) or by dipping. you take of your shakes and shingles, coverings gradually degrade from the For the purposes of this discussion, the longer you can expect your roof to effects of sunlight and from the when we mention shingles and shakes, last. erosion of winds, rain, and snow. redcedar is the species we mean. Assuming that moss is controlled, current asphalt roofs tend PUBLICATIONto have a fixed term of usefulness that rarely can be Weathering extended. Shingles or shakes? When wood is exposed to the But care and maintenance can There's a difference between effects of sunlight and precipitation, extend the life of woodmost shingles or shingles and shakes. Shingles in all its surface begins to change. This shakes.THIS With an extended life, it may instances are sawn; shakes can be be possible to obtain a real saving in split, split and sawn, or simply sawn, dollars andFor cents and make your depending on the type and grade you Stanley S. Niemiec, research assistant. wooden roof more cost-effective. chose. Department of Forest Products, and This publication will discuss the Initial coverage (bundles of Terence D. Brown, Extension forest specific methods http://extension.oregonstate.edu/catalogfor extending the material per 100 square foot of roof products specialist, Oregon State number of years that a wood shingle area) of a roof depends on the type of University.

OREGON STATE UNIVERSITY EXTENSION SERVICE change is partly physical and partly chemical, and it's cumulatively referred to as weathering. The first noticeable change is the color. The initial red-brown color tends to fade, and a graying process begins. This change to silvery gray is the result of ultraviolet (UV) radiation from the sun which strips the surface layer (less than 0.01 inch deep) of certain cell-wall materials. This first change in color is rather rapid, occurring within the first year of exposure (under more severe condi- tions, within several months). Gradu- DATE. ally, the silver gray will change to a darker, more graphite gray, indicating the surface is being colonized by OF microfungi, a step that completes the initial phase of the weathering process. By nature, wood rapidly attracts water to its surface. When this OUT happens, the wood swells. As it dries and the moisture content decreases, it shrinks. This repeated wet-dry cycling IS causes the development of compres- sion and tension stresses; these, in turn, cause microscopic cracks to develop. Over time, these cracks grow larger and larger, caused by additional information: wettings or by freezing and thawing. The cracks also trap water and allow wood-rotting organisms to penetrate deeper into the wood. As the water penetrates more deeply, the wood becomes harder to dry. With increased moisture, the wood-rotting organismscurrent prolong their destructivePUBLICATION activity and damage more wood material than Figure 1.—Moss growing on shingles and shakes does double damage: (1) during would occur during normal weather- a rain. It retards the shedding of water, which in turn promotes leaks; and (2) after ing. the rain stops, moss prevents the surface from drying, which promotes the growth As the roof continues to age, the of wood-rotting organisms. surface and sharp edgesmost from manu- THISfacturing are eroded by abrasive particles carried in wind and water and by the action of sunlight. Wood- destroyingFor organisms also continue to slowly degrade the surface and the thicker butt edge.http://extension.oregonstate.edu/catalog The roof loses its new appearance. Debris from trees accumulates in the valleys and between the shingles. lichens and mosses (Figure 1). More cupping and curling begin to become After each rain, there are areas that debris collects, and the roof appears to more apparent. Then the leaks begin. stay wetter longer. Soon, other plants be natural and rustic. There are splits Sometimes, this takes 30 years— are beginning to grow, primarily developing, and in certain areas sometimes, much less. Care and maintenance Good housekeeping for a wood roof requires removing all leaf litter, pine needles, and debris that accumu- late over time between the shingles and shakes and in the valleys of the actual roof structure. It's best to do this before the wet season begins. In the Pacific Northwest, this is before the autumn rains begin. Along the Gulf Coast or in areas that are conducive to the growth of molds, mildews, and fungi, this housekeeping may be required several times each year. DATE. The debris that accumulates has two deteriorating effects on the roof. First and foremost, debris tends to OF retard the shedding of water. Sec- ondly—and more destructively— debris retains moisture that allows wood-destroying fungi to grow. Wood-rotting fungi require water OUT as part of the life cycle. If you can Figure 2.—High-pressure washers are effective in cleaning roof surfaces of debris reduce the amount of water so that the and moss. Be careful when you use them in order to prevent unnecessary erosion minimum level is never reached, the of the shingle or shakeIS surfaces. organisms can't grow. To promote drying, it's very important to remove overhanging branches that excessively shade around chimneys and in valleys, but sections and retard the drying of the you'll also need to clean all the roof surface. Never allow tree keyways (those areas between the Roof safety precautions branches to touchinformation: and rub against the individual shingles and shakes). The • Use footwear that will provide good surface of the roof. The mechanical wet sweeping of the surface in a traction and grip the roof surface action of this rubbing can literally careful manner will additionally (avoid leather-soled shoes). wear sweeping grooves into the remove the initial growths of moss • Use a ladder that meets all safety surface of the shingles or can loosen and lichens. requirements. Check the ladder to the fasteners that hold them. Professional services sometimes ensure that it is in good condition Finally, in excessively woody use high-pressure washers (available and good working order, that it is currentareas, branches may retard the flow of through rental firms, Figure 2). These set on stable, levelPUBLICATION ground, and that air so that surface drying may occur are effective, but you must use ex- it is set at the proper slope. very slowly. In all cases, you'll need treme care because cedar is a soft, • Your ladder should extend at least 3 to make sound judgments about low-density wood. Excessive or im- feet above the roof line. Tie it off at pruning, trimming, or removing prudent use of high-pressure systems the top. problem-causing trees. Excessive can detach shingles or erode many • Use a bucket and ropemost to transport growth of lichens and mosses is a sure years of wear in moments—even THIStools, etc., to the roof. Don't carry indicator that your roof is not drying though the roof will "look like new." them up the ladder. properly—and that enough moisture is If you don't choose to climb on • As muchFor as possible, walk across available to support wood-rotting your roof, you can hire a professional. the roof surface rather than up and organisms. Look in your phone book under either down. Removing the debris accumulation "Moss control" or "Roofing contac- • On slopes withhttp://extension.oregonstate.edu/catalog a 5-12 pitch (about is relatively simple. In most cases, tors." As you would with any contract 23°) or greater, use safety lines and anyone who's willing to climb on the for service, choose a reputable firm belts. On roofs more than 16 feet roof can wash off most of the material that can provide proof of insurance, from eave to ground, use safety with a garden hose. And a stiff broom references if you ask for them, a lines and harnesses when you work is handy for removing all the leaf and written description of the work to be within 6 feet of the edge. pine needle litter. done, and an estimate of the amount It's easiest to remove litter from you'll be charged. Some further tips: It's best to use Chemical treatments these solutions out of direct sunlight. There are several types: Use pesticides safely! Apply the chemical only to the stain. 1. You can easily prepare cleaning • Wear protective clothing and safety Avoid drips, runs, and splashes of solutions to help remove dirt, mild devices as recommended on the bleach or excessive bleaching on the stains, and light growths of molds and label. Bathe or shower after each roof surface—these can mar the roofs mildew. use. appearance. It's not necessary to scrub 2. For more persistent stains, • Read the pesticide label—even if bleached areas, but rinse the wood bleaching formulations will be you've used the pesticide before. thoroughly. recommended. Follow closely the instructions on 3. In some cases of excessive moss the label (and any other directions Chemical solutions growth, you can apply chemical you have). for moss control solutions to kill the mosses and any • Be cautious when you apply fungi that may be present. Note: It's extremely important to 4. You may sometimes apply pesticides. Know your legal be carefulDATE. when you apply the preservative chemical solutions that responsibility as a pesticide applica- chemicals listed in the following tor. You may be liable for injury or will retard the growth of molds, fungi, pages; otherwise, you can seriously damage resulting from pesticide use. and mosses. OFharm surrounding vegetation and— 5. Finally, additives such as more important— people or pets. pigments and ultraviolet absorbers These chemicals often carry promi- can slow deterioration caused by nent warnings about exposure or ingestion. sunlight. Apply this mixture and scrub the Remember: The chemicals you Considered as a whole, the chemi- surface with a soft brush or lightly OUT apply to roofs to remove existing cals in steps 3 and 4 are chosen for with a broom. Then rinse the surface growth or prevent its recurrence are their fungicidal or herbicidal effects. with water to eliminate any residue. If toxic— handle them with care! If you It's important to note that the chemi- you accidentally ISsplash any plants, have any doubts about safe handling, cals listed in the following sections rinse them thoroughly. will perform differently under various write the manufacturer, see your environmental conditions. As a result, county Extension agent, or phone the the frequency of application required Bleaching formulations closest poison control center (see the for long-term protection depends on list on page 8). the chemical you use, the amount of For more persistent stains, you can When there's so much moss that precipitation, average temperatures, increase the information:sodium hypochlorite patches or mats are present, abrasive and the roof exposure conditions. The (chlorine bleach) concentration, even removal by sweeping may not remove chemicals we recommend are avail- to the point of using it full strength it all. Scraping may not be possible able in products sold in hardware from the bottle for spot applications. because of the contours of the shakes, stores, building supply centers, or Formulate stronger solutions by and it may damage the roof surface. lumber yards. using granular chlorine (calcium In these cases, applying moss- hypochlorite), mixed at a rate of 2 killing chemicals or using high- Cleaning solutions currentounces per gallon of water. This pressure washers (or both) may be a PUBLICATIONchemical is used for algae control in more effective method for removing You've removed the debris from swimming pools and is available the residual growth. Remember that your roof, and you can see light through pool supply houses. the wood surface may not dry under a staining or irregular discoloration. For safety, wear eye protection, covering growth of moss. And this wet Cleaning the roof withmost a mild deter- rubber gloves, and aprons. condition promotes the growth of gent solution may provide an improve- It's best to apply these bleaches wood-decaying fungi. THISment. The recommended solution is: with brushes for small spots; spray Moss-killing chemicals are • 3 ounces trisodium phosphate large areas (use plastic or stainless recommended in the following order (alsoFor known as TSP, available in steel sprayers). Don't let bleaching of effectiveness (most effective first): paint or hardware stores) solutions remain on the wood for more than half an hour before rinsing. Zinc sulfate (monohydrate). • 1 ounce detergent (for example, http://extension.oregonstate.edu/catalogExperience shows these solutions Mix 3 pounds powder in 5 to 10 Tide or All) provide more uniform results when gallons of water and apply to 600 • 1 quart 5% sodium hypochlorite you use them in lower concentrations; square feet of moss growth. Apply (liquid bleach—Clorox, for repeat the application, rather than use higher concentrations to exceptionally example) a single high concentration when you heavy growths or where conditions • 3 quarts warm water start. favor moss growth. Use a watering can or pump sprayer. Don't use this runoff and to increase effectiveness, especially in enhancing the natural solution if you have copper gutters, apply when rain is not likely, for it decay-resistant extractives within the downspouts, or flashings, because zinc may be several days before the growth wood and because of the potential sulfate corrodes copper. is killed and you can effectively UV-radiation protection imparted remove it by sweeping it from the from pigments or other additives. Copper sulfate (also called blue surface of the shingles or shakes. When you apply preservative stone). Mix 0.25 to 0.5 ounce per 10 Remember to use care when chemicals to shakes and shingles, you gallons of water. This chemical is also handling and disposing of moss and need to remember several important corrosive to metals—although safer litter treated with chemicals to avoid considerations. than zinc sulfate for copper flashings accidental exposure. First, the coating should be as — so be cautious where you apply it. Some of the chemicals listed earlier uniform as possible. Avoid drips and Wash all exposed gutters, flashings, will provide minimal protection runs, if possible. It's better to apply and application equipment thoroughly. against future growth, depending on several light coats and obtain good Apply the same way you would apply the concentration applied and the ex- absorption than to try and force it in zinc sulfate. posure conditions. As a whole, all at once.DATE. The important point is that however, their long-term effectiveness you're trying to reach a certain level Zinc chloride. Mix 1 pint in 3 is limited, and you should consider of preservative retention. If the gallons of water. Apply at rate of 3 them only to kill existing growth. OFretention level is too low, your gallons per 100 feet of moss area by The corrosive nature of these treatment will be ineffective. thoroughly soaking the moss but chemicals means that you must pre- Second, since much of the decay avoiding runoff. Because zinc chloride vent unnecessary damage by thor- occurs in the butt region of the shingle is corrosive to metals and harmful to oughly rinsing metal tools, gutters, or shake, it's a good idea to be plants, dilute all spills or accidental and flashings that have comeOUT in conscientious when you apply the applications to plants by spraying with contact with the solutions. solutions, making sure to cover the water. Apply it the same way as zinc exposed butts as well as the exposed sulfate. IS shingle surface. Preservative treatments The three methods available to Potassium salts of fatty acids. Chemical solutions may also be provide proper application are These soap-based, biodegradable applied to redcedar shingles and brushing, using a thick-napped roller, products kill the moss by penetrating shakes that will retard the growth of or spraying. Because of the irregular the cell walls and changing the molds, mosses, and (more impor- surface, you'll probably get a more membrane characteristics, causing the tantly) wood-rottinginformation: fungi. These uniform coating with a multigailon, loss of cell contents. These chemicals chemicals are most commonly pump-type sprayer set to produce a are noncorrosive and offer minimal referred to as wood preservatives, and coarse spray. hazard to people and animals. Even they're an effective means of extend- Spraying also requires a calm day so, overspray on plants and foliage ing the life of your roof. (wind less than 4 mph) to prevent still requires thorough rinsing. When you apply preservative spray from drifting over plants or into chemicals to your roof, the roof your neighbor's yard. Brushes are also Other weed-killing (proprietary)current condition at the time of treatment will effective because they allow for the compounds. SomePUBLICATION compounds used determine the actual amount of thorough treatment of the key ways as weed killers are effective for moss increased longevity. If a roof has aged and ends. control and are available at garden for many years, the treatment won't be The chemicals listed on pages 6 supply centers. Follow manufacturer's as effective— simply because the and 7 will most likely be part of directions and precautions for use. years of exposure will have taken their formulations in over-the-counter Any of these chemicalsmost are more toll. In all instances, except when the products or part of the formulations effectiveTHIS if applied when the moss is roof is badly deteriorated, you can applied by roof servicing contractors. actively growing than when it's in the expect preservative chemicals to These chemicals are also available in dormant phase.For Moss grows vigor- extend the life of your roof. concentrated form but only through ously during the rainy seasons—in It's best to apply preservative specially licensed supply companies. Oregon, this is during the late fall, treating solutions to wood shingle and This is because of the toxicity, winter, and spring.http://extension.oregonstate.edu/catalog There's very little shake roofs as soon as possible after possible problems in preparation, and growth during the summer. the wood has gone through an initial the limited demand from home If you plan to apply the chemicals weathering process. Treatment should owners. during dry periods, it's often recom- be within 3 to 12 months of the roof's In every case, regardless of the mended that you wet the moss first to installation because of the general concentration you use, be extremely promote chemical uptake. To control effectiveness of the treating solutions careful when you apply, handle. DATE. OF

OUT IS

Figure 3.—Below this zinc chimney flashing, moss growth was strips across the roof surface (as an alternative to toxic inhibited, as indicated by the lighter colored roof surface. This chemicals) to retard moss growth. leads some wood scientists to recommend using copperinformation: or zinc

expose, and store the chemical. When Literature indicates that using this metal content — for example, 2% to you purchase over-the-counter concentration will provide up to 5 3% solutions for 3 years of protection products for long-term moss control,current years of protection in the Pacific (or 4% for 5 years) per 100 to 150 be sure one of thePUBLICATION wood-preserving Northwest. Note that copper naph- square feet, as specified in the preced- chemicals listed below appears on the thenate has a greenish color that may ing section on copper naphthenate. label. prove unsightly. To overcome this, Currently, the preservatives in the choose a solution that's pigmented to MTC (methyl bis [thiocyanate]) following sections mostare available as simulate the red-brown cedar tones, or and TCMTB (2-[thio cyanomethyl THISeither aqueous solutions or oil-based use another type of preservative. thio) benzo-thiazole). These generally products. are used in combination as an effec- Zinc naphthenate. While copper tive roof treatment. They can be used CopperFor naphthenate. This is an is a much more effective chemical in clear coatings or in pigmented effective preservative well suited for than zinc in retarding the growth of solutions, and either as waterborne applying to roofs.http://extension.oregonstate.edu/catalog Solutions should biological organisms, zinc solutions solutions or with solvent/oil mixtures. consist of at least 1% copper (2% is are used by people who wish to retain better); apply them at a rate of 1 the more silver or gray appearance on Copper 8 quinolinolate While gallon per 100 square feet for shakes the roof surface. It's best either to this chemical is a safer alternative to and 1 gallon per 150 square feet for make more frequent applications or to those listed above, some tests indicate shingles. use higher concentrations of active its effectiveness is short-lived. It's not very effective in controlling moss or zinc strip will remain effective or how but they also obscure the natural color mildew on roofs for much more than much metal is required. Its effect of the roof. However, pigments can be 12 to 18 months. below chimney flashings can be seen mixed to imitate natural hues ranging for at least 15 feet and appears to last from a weathered silver-grey to the 3-iodo 2-propynyl butyl carbam- for the life of the flashings. roofs original red-brown color. ate (Polyphase). In solutions where If your roof is so large that the Clear, organic-based additives concentration levels are greater than material at the ridge doesn't retard impart no color to the roof but are 0.58% to 2.0% activeingredient, you moss growth at the bottom, place short lived—generally, less than 2 might get 2 years of protection. The additional strips across the surface. years. In the longer term, pigments durability and long-term performance After a year, you should be able to give better results and therefore are the of this product is still unknown, but judge how well the strips are control- recommended additive for roof it's limited because of light and water ling the growth of moss. Add more treatment solutions. sensitivity. strips if they're needed. The greater effectiveness of copper Tri-butyltin oxide (TBTO). over zinc has been noted with copper DATE. Some literature indicates its use is and zinc naphthenate. So copper strips Oil treatments questionable in treating existing roofs are also likely to control moss, and Oils are sometimes advertised to because of mold and mildew resis- possibly retard wood-decaying OFreplenish "the natural oils in the tance and chemical degradation. It's organisms, because of the greater wood." In redcedar, these oils account often used together with trichloro- effectiveness of the copper. This fact for less than 3% of the total mass. methyl thio phthalimide (Folpet), has been observed below copper While they do contribute to dimen- which has weak fungicidal properties. flashings. sional stability and decay resistance, In one case, a roof was observedOUT applying "replenishing oils" to Pentachlorophenol. Though that would be considered a favorable weathered shingles may be of ques- widely available in the past, this site for moss growth. Two strands of tionable value especially if they product is no longer available over the 10-12 gauge copperIS wire had been contain no preservative or water- counter because it presents health and placed, one near the ridge and one repellent chemicals. environmental risks. some 15 feet below (at the halfway You might get some temporary If you have solutions con- point on the slope). No moss was benefit, however, with regard to taining this chemical, do observed growing. As with the zinc controlling cupping and warping. But not apply them. Contact strips, we couldn't find any supporting some information indicates that the Oregon Department scientific studiesinformation: to confirm these applying oils may have some limiting of Environmental Quality methods, but those willing to try may factors. The main limitation is that about proper disposal. obtain favorable results. unless you include an effective mildicide or preservative, an oil like Zinc and copper strips For those Chemicals under evaluation. A linseed may provide an additional who prefer not to use toxic chemicals, number of compounds collectively food source for mold, mildew, and there appear to be safe and relatively termed quaternary ammonium fungi. inexpensive treatments to control currentcompounds have shown promise and Furthermore, petroleum-based moss growth. GalvanizedPUBLICATION metals have may be available shortly. products are likely to be oxidized a surface coating of zinc. For example, (broken down) by sunlight, to have if you fasten a 2-inch-wide strip to only a short-lived effect, and to either side of the ridges and run it the UV protection increase the flammability of your roof. entire length of the roof,most rain will Ultraviolet (UV) radiation from the leach zinc from the metal's surface sun degrades exposed wood surfaces andTHIS wash it down the roof. by breaking down cell wall materials. As we noted earlier ("Zinc This part of roof deterioration can be Roof leaks sulfate," pageFor 4), zinc can effectively reduced with additive compounds that A word of warning: At the time of kill or retard the growth of mosses and block or absorb UV rays. this writing, there's nothing available fungi. Its effect has long been noted in Two types of material provide that you can apply to a shingle or personal correspondencehttp://extension.oregonstate.edu/catalog between some level of protection: pigments, shake roof that will stop it from wood scientists; this effect is promi- and clear, organic formulations. leaking. Leaks generally indicate nent below chimney flashings and Pigments generally are powdered either damage or deterioration of the vents (Figure 3). substances added to the treating roof. In these cases, it's advisable to However, we couldn't find any solutions to impart color. Pigments are seek the advice and services of a scientific study to verify how long a inexpensive, durable, and effective. reputable roofing contractor. New products may become The Red Cedar Shingle and Handsplit Washington available in the future, but be sure of Shake Bureau, 515 116th Ave. HE, Spokane Poison Control the effectiveness of the product before Bellevue, WA 98004. St. Luke's Hospital Emergency Room you spend your money. If you have Buchanan,Brian. \9%\.Evaluating South 711 Cowley doubts about a company, check with Various Preservative Treatments and Spokane, Washington 99202 your local Better Business Bureau. Treating Methods for Western Redcedar phone toll-free from all locations Shingles. Publication 128, Texas Forest 1 (800) 572-5842 Conclusion Service, Texas A&M University. No Central Washington Poison Center Wooden roofs are an asset to the charge for a single copy; order from Yakima Valley Memorial Hospital homes or buildings to which they're Texas Forest Products Laboratory, P.O. 2811 Tieton Drive applied. Their natural appearance and Box 310, Lufkin, TX 75902. Yakima, Washington 98902 inherent properties make them well phone (509)248-4400 suited to provide durable and attrac- Washington toll-free tive roofs. By using simple, inexpen- DATE. Poison Control 1 (800)572-9176 sive housekeeping techniques on a Centers regular basis, it's possible to extend Seattle Poison Center the Jife of the roof. Applying moss- Oregon OFChildren's Hospital and decay-retarding chemicals helps 4800 Sandpoint Way NE Oregon Poison Control obtain even longer service from the P.O.BoxC-5371 Oregon Health Sciences University roof system, makes it more cost Seattle, Washington 98105-0371 Room 2519, effective, prevents costly repairs, and phone (206)526-2121 University Hospital North preserves the resource. Washington toll-free But if you climb on your roof to 3181 SW Sam Jackson ParkOUT Road 1 (800) 732-6985 apply these treatments, be careful— Portland, Oregon 97201 phone (503) 494-8968 use good judgment and follow safe IS Mary Bridge Poison Center Oregon toll-free procedures. When you handle Mary Bridge Children's Hospital 1(800)452-7165 chemicals, be careful to follow all and Health Center directions on the manufacturers' 317 South K Street labels. Idaho Tacoma, Washington 98405-0987 Poison Control Center Washington toll-free St. Alphonsusinformation: Hospital 1 (800)542-6319 For further 1055 North Curtis Road information Boise, Idaho 83706 phone (208) 378-2707 For design criteria, contact an archi- Idaho toll-free tect, building or roofing contractor, or 1 (800) 632-8000 PUBLICATIONcurrent most THIS This publication replaces Extension publication FS 10. Trade-name products are used as illustrations only. Their mention does not mean that Oregon State University Extension Service endorses these products or intends to discrimi- For nate against products that are not mentioned. Extension Service, Oregon State University, Corvallis, O.E. Smith, director. This publication was produced and http://extension.oregonstate.edu/catalogdistributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties.

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