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.