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Home , Clapboard, Reveal (carpentry), Siding (construction), Wood grain

Wood – Installing, Finishing, Maintaining

United States PREPARED BY Home and Garden Department of Forest Service Bulletin 203 Agriculture Contents

Page Introduction ...... 3 Types of Siding...... 4 ...... 4 ...... 6 Reconstituted Wood Products 7 Selecting Wood Siding...... 8 Installing Wood Siding...... 8 Horizontal Siding...... 8 Plywood and Other Sheet Siding...... 10 Shingles and Shakes...... 11 The and Moisture...... 12 Types of Wood Finishes...... 14 ...... 14 Solid-Color Stains...... I5 Semitransparent Penetrating Stains ...... 15 Water-Repellent Preservatives. 15 ...... 17 Preservatives...... 17 Applying Wood Finishes...... 18 Paint...... 18 Additional Tips on Painting. . 19 Solid-Color Stains...... 20 Semitransparent Penetrating Stains ...... 20 Water-Repellent Preservatives. 21 Refinishing...... 22 Paint ...... 22 Solid-Color Stains...... 22 Semitransparent Penetrating Stains ...... 22 Water-Repellent Preservatives. 22 Warnings...... 23

Revised December 1983 Wood Siding—Installing, Finishing, Maintaining by W. C. Feist and A. E. Oviatt1

Introduction

Wood siding is put on for and nailed into place. Other many good reasons. reasons are its fuel-saving value, One reason is that it will keep the because of the millions of tiny bright new “face” of any home at- hollow fibers that make it a good tractive for many years to come. In insulator, and its natural resistance fact, given reasonable care, wood to the ravages of weather. siding will retain its beauty for cen- Other reasons to use wood siding turies, as has been amply proved by include its ability to hold a wide its performance on houses that date variety of finishes-clear ones that back to early colonial times. It also reveal and accentuate its natural has great versatility; and the large beauty, stains that impart a rustic variety of patterns, sizes, and colors appearance, and of every allows for effects ranging from the conceivable color. Within limits, simple charm of colonial the color scheme can be changed to the rustic beauty of board-and- periodically to give a home a fresh and rough-textured plywood new appearance in keeping with or lumber siding. In between are changing times. It is little wonder many other varieties and combina- that wood siding has come to stand tions that produce distinctive and for warmth, comfort, security, attractive effects. beauty-all the things that spell Then there is the ease and speed “home.” with which it can be sawed, fitted,

1Chemist and Forest Products Technol- ogist (Retired), USDA Forest Service, Forest Products Laboratory, Madison, Wis. The laboratory is maintained in cooperation with the University of Wisconsin.

3 Types of Wood Siding

Many kinds of wood siding are heavy compared to the lighter on the market today. All will give weight ones such as redwood and good service, provided each is used cedar. The weight of wood is im- properly. portant because heavy shrink There are three general categories and swell more than light ones. of wood siding commonly used in This dimensional change in lumber construction. These are lumber, occurs as the wood gains or loses plywood, and reconstituted wood moisture. Wood in heated homes products such as and tends to dry and shrink in the particleboard. Each product has winter and gains moisture and unique characteristics that will affect swells in the warm summer months. the durability of any finish applied Excessive dimensional change in to it. wood consistently stresses a paint film and may result in early failure. lumber Some species have wide bands of Lumber is being used less and dark, dense wood alternating with ‘less as exterior siding, but was once bands of light, softer wood. The the most common wood material light bands are formed in the spring used in construction. Many older of the year and are called homes have wood siding. The abil- earlywood. The dark bands are ity of lumber to retain and hold a formed in the summer and are call- finish is affected by species, by ed latewood (fig. 1). Bands of grain direction or how the piece latewood are characteristic of was sawn, and by smoothness. southern yellow and some The weight of wood varies greatly boards of Douglas-. Paint will not between species. Some common hold well on these species, and construction woods such as penetrating stains are preferred. On southern yellow pine are dense and the other hand, wide latewood

Figure 1–Earlywood and latewood bands in southern yellow pine. These distinct bands often lead to early paint failure. Therefore, penetrating stains are preferred. M830023

4 bands are not characteristic of red- Paint will last longer on smooth, wood and cedar; therefore, these edge-grained surfaces. Penetrating species are recommended when stains or preservative treatments are paint will be used. preferred for rough-sawn lumber. Grain direction also affects paint- These treatments often accentuate holding characteristics and is deter- the natural or rustic look of rough- mined at the time lumber is cut sawn lumber and allow the wood from a log. Lumber is referred to as grain and surface texture to show flat-grained, edge-grained (quarter- through the finish. sawed), or a combination of the For houses, siding is two (fig. 2). Most standard lumber perhaps the most widely used. (See contains a high percentage of flat fig. 7.) Drop siding and pat- grain. terns are also used, especially on Lumber used for board-and-batten buildings without sheathing. These siding, drop siding, or shiplap is fre- patterns of siding are applied quently flat-grained. Bevel siding of horizontally and tend to make a redwood or cedar is often, but not house appear lower and longer. always, manufactured so that it is Vertical siding is increasingly edge-grained. Edge-grained bevel popular. It consists of tongued-and- siding will hold paint well. Flat- grooved boards or squareedged grained lumber will not hold paint boards applied vertically, often with as well since it shrinks and swells narrow strips called nailed more than edge-grained lumber and over the joints. Vertical patterns because wide, dark bands of with smooth and rough-sawn sur- latewood are frequently present faces are available in plywood of (fig. 3). Douglas-fir, redwood, and western

Figure 2–Edge-grained (or quarter- sawed) board (left) and flat-grained (or plainsawed) board (right) cut from a log. M147253 5 Figure 3–Paint applied over edge grained boards (top and bottom) per- forms better than that applied to flat- grained boards (middle). M147211-7

redcedar. Vertical siding tends to The flat-grained pattern present in make a house appear taller. nearly all plywood can also con- tribute to early paint failure. Plywood Therefore, if smooth or rough-sawn plywood is to be painted, special Exterior plywood with a rough- precautions should be taken. sawn surface is commonly used for Penetrating stains are often more siding. Smooth-sanded plywood is appropriate for smooth-sanded and not recommended for siding, but it especially rough-sawn exterior may be used in soffits. Both sanded plywood surfaces. and rough-sawn plywood can Plywood manufactured with a develop surface checks, especially mediumdensity overlay is fre- when exposed to moisture and quently called MDO. Compared to sunlight. These surface checks can standard rough-sawn or smooth lead to early paint failure with oil plywood, MDO holds paint well. or alkyd paint systems (fig. 4). MDO plywood is not always a Quality acrylic latex paint systems stock item in many lumber yards, generally perform better. but it can usually be ordered. Figure 4–Early paint failure on plywood because of penetration of moisture into surface checks of plywood. M830013-6

Reconstituted Wood Products eled drop siding, traditionally made from solid wood. Reconstituted wood products are Particleboards are manufactured those made by forming small pieces from whole wood in the form of of wood into large sheets, usually 4 splinters, chips, flakes, or shavings. by 8 feet, or as required for a and flakeboard are two specialized use such as beveled types of particleboard made from drop siding. These products may be relatively large flakes or shavings. classified as or par- Only some and par- ticleboard, depending upon the ticleboards are manufactured for ex- nature of the basic wood terior use. Film-forming finishes component. such as paints and solid-color stains Fiberboards are produced from will give the most protection to mechanical pulps. Hardboard is a these reconstituted wood products. relatively heavy type of fiberboard Some reconstituted wood products and is used for exterior siding. It is are factory primed with paint and often used as a substitute for bev- some even have a top coat.

7 Selecting Wood Siding Installing Wood Siding

The kind of siding chosen will de- Horizontal Siding pend on where the house is built, its price range, and the architectural Wood siding is simple to install. effect wanted. A range of quality in It is precision manufactured to lumber and wood-based panel pro- standard sizes and is easily cut, fit- ducts is available from clear, ted, and fixed in place with or- smooth edge-grained to rough, flat- dinary tools. grained with knots. These and other Courses of horizontal siding visual characteristics should be should be spaced so that a single given special finishing treatments in board runs continuously above and accord with the effects wanted. below windows and above Many species of wood can be without notching: Bevel siding that used for siding. In siding cut from is 6 inches wide should have at lumber, medium decay resistance, least 1 inch of overlap between freedom from warping, low courses. Siding that is 8 inches or shrinkage, easy working qualities, wider should overlap 1 to 1½ and good finishing characteristics inches, depending on spacing re- are desirable. quired between window heights Among the species with all or (fig. 5). most of these qualities are the cedars, redwood, the white , the , and yellow-poplar. Douglas-fir and the southern pines are also used in the better clear grades. The dense h very limited local use.

Figure S-Installation of bevel siding. ML835110

8 Siding should be butted snugly (fig. 6). Mitered corners should be and squarely against and win- precisely fitted for the same reason. dow casings, corner boards, and ad- To fasten siding in place, zinc- joining boards. (Corner boards coated, aluminum, or other noncor- should lie flat against the rosive nails are recommended. Plain sheathing.) If metal corner covers steel-wire nails, especially the large- are used, siding boards should be headed type that are designed for carefully cut to avoid leaving a flush driving, make unsightly rust hollow place under the corner spots on most paints. Even small- cover where water could collect headed plain steel nails, counter-

A

Figure 6–Recommended procedures for corners of siding: (A) Miter corners, (B) metal corners, (C) corner boards, and (D) interior corner. M134776

9 sunk and puttied, are likely to spot applied vertically. When used over the finish with rust. Naturally fin- sheathing, plywood should be at ished siding is installed best with least 1/4 inch thick, although 5/16 aluminum or stainless steel nails. and 3/8 inch will normally provide For best performance, nailing pat- a more even surface. Hardboard terns for the various kinds of siding should be l/4-inch thick and are very important and should com- materials such as mediumdensity ply with the recommendations of fiberboard should be l/2-inch thick. the manufacturers (fig. 7). All nailing should be over studs, and total effective penetration into Plywood and Other Sheet Siding wood should be at least l-1/2 inches. For example, 3/8-inch Exterior-grade plywood, paper- plywood siding over 3/4-inch wood overlaid plywood, and similar sheet sheathing would require about a materials used for siding are usually sevenpenny nail, which is 2-1/4

Figure 7–Patterns of wood siding and recommended nailing practices: (A) Horizontal application, and (B) vertical application. M139819

10 inches long. This would result in a colonial and styles as 1-1/8 inch penetration into the stud, well as more contemporary designs. but a total effective penetration of They may be applied in single- or 1-7/8 inches into wood. double-course patterns. It is per- Plywood should be nailed at missible for singlecourses to have a 6-inch intervals around the larger exposure on sidewalls than perimeter and at 12-inch intervals in on roofs, as the vertical per- the middle. Hardboard siding mits faster drainage and reduces should be nailed at 4- and 8-inch wind-blown penetration of water. intervals. All types of sheet material Headlap (the amount of lap over should have a joint caulked with the second course below) may be mastic unless the joints are of the as little as 1 inch (fig. 8). interlapping or matched type or bat- Doublecourse application results tens are installed. Putting a strip of in deeper shadow lines at the dou- 15-pound asphalt felt under un- ble butts. The first course may be of caulked joints is good practice. lower quality such as grade 3; but the top course should be grade 1, since much of the shingle or shake Shingles and Shakes is exposed (fig. 9). Some wood-based panel products Wood shingles and shakes have have simulated shingle appearances also been used as siding since col- or have premounted shingles on a onial times, and remain popular on backing panel.

Figure 8–Single-coursing of sidewalls Figure 9–Double-coursing of (wood shingles or shakes). M134610 sidewalls (wood shingles or shakes). Ml34609

11 The House and Moisture

Wood siding is a part of the water or frost in the siding during house; therefore, its performance is the winter. With the return of warm vitally affected by the rest of the weather in the spring, this moisture structure. The whole house must be can-and often does-cause the ex- properly built to insure long-lasting terior paint to blister. The problem service. has been further accentuated by air Insulation, weatherstripping, and conditioning and by humidifying. generally tight construction reduce A number of measures can be fuel bills and make for comfort, but taken to help keep moisture out of their misuse may create some paint . One of the most effective is problems. to put a good vapor barrier under Water vapor formed within a the plaster, drywall, or paneling. house moves through the inner sur- Asphaltcoated paper, aluminum faces of the outer walls because of foil, and polyethylene film are differences in temperature between satisfactory vapor barriers for homes the inside and outside. This water (fig. 10). vapor condenses and collects as

Figure 10–Vapor barrier (on warm side of ) has prevented moisture from getting into walls. ML835109

12 Rain and snow water must be and attic spaces ventilated so heat kept out, too. Roof gutters must be losses do not melt snow on roofs to sloped and have enough down- produce ice dams and clog gutters spouts or they may overflow during (fig. 11). rainstorms and let water seep into Wide roof overhangs help in walls through joints in the siding. keeping moisture out. So, too, does Attic floors should be well insulated metal flashing in roof valleys, along

Figure 11–Ice dams: (A) Insufficient insulation and ventilation can cause ice dams and water damage; and (B) Good ventilation, insulation, and roof flashing minimize problems. M134787

13 Types of Wood Finishes

dormers, and around chimneys Paint (fig. 12). Window and door frames also need adequate cap flashing. Paints are common coatings used A comparatively simple treatment on wood and provide the most pro- for siding helps keep water out of tection. They come in a wide range wood. Siding can be dipped in a of colors and may be either oil or water-repellent preservative before it latex based. Latex-base paints and is installed or the water-repellent stains are water borne, and oil or preservative can be brushed on after alkyd paints are solvent borne. the siding is installed, but before it Paints are used for decorative pur- is painted. These preservatives are poses, to protect the wood surface sold by lumber dealers and some from weathering, and to conceal paint stores. They contain certain defects. fungicides, resins, and waxes (water Paints are applied to the wood repellent) that cause water to run surface and do not penetrate it off instead of penetrating into the deeply. The wood grain is com- wood at end and lap joints. pletely obscured, and a surface film

Figure 12–Metal flashing along dormers helps keep moisture out of siding; the flashing extends back of siding and under shingles. ML835330

14 is formed. This surface film can Semitransparent Penetrating Stains blister or peel if the wood is wetted or if inside water vapor moves Semitransparent penetrating stains through the house wall and wood are popular for rustic finishes. They siding because of the absence of a are moderately pigmented and thus vapor barrier or one that is do not totally hide the wood grain. defective. These stains penetrate the wood Latex-base paints are generally surface, are porous, and do not easier to use since water is used in form a surface film like paint. As a cleanup. They are also porous and, result, they will not blister or peel thus, will allow some moisture even if moisture gets into the wood. movement. In comparison, oil-base Penetrating stains are alkyd or oil paints require organic solvents for based and usually contain a cleanup, and some are resistant to fungicide or water repellant. Latex- moisture movement. base (waterborne) stains are also Paints perform best on smooth, available, but they do not penetrate edge-grained lumber of lightweight the wood surface as do the oil-base species such as redwood and cedar stains. and on hardboard and overlaid Stains are most effective on rough plywood. Paints are the only way to lumber or plywood surfaces, but achieve a bright white finish. they also provide satisfactory perfor- However, they are subject to peel- mance on smooth surfaces. They ing where moisture is a problem. are available in a variety of colors Paint is best for smooth surfaces; and are especially popular in the stains and preservatives, for rough brown tones since they give a surfaces. natural or rustic wood appearance. They are not available in white. Solid-Color Stains They are also an excellent finish for weathered wood. They are not ef- Solidcolor stains, also called fective when applied over a solid- heavy-bodied stains, are opaque color stain or over old paint and are finishes, which come in a wide not recommended on hardboard or range of colors and are defined as similar reconstituted wood panel stains. Solidcolor stains are made products. with a much higher concentration of pigment than the semitransparent Water-Repellent Preservatives penetrating stains described below. As a result, they will obscure the A water-repellent preservative natural wood color and grain. Oil- may be used as a natural finish. It base solidcolor stains tend to form contains a fungicide (usually pen- a film much like paint, and as a tachlorophenol or copper result, can also peel loose from the naphthenate), a small amount of substrate. Latex-base solid-color wax as a water repellant, a resin or stains are also available and form a drying oil, and a solvent such as film as do the oil-base solid-color turpentine or mineral spirits. Water- stains. These stains are similar to repellent preservatives do not con- thinned paints. tain any coloring pigments.

15 Therefore, the resulting finish will fungicide inhibits surface decay or vary in color depending upon the mildew. kind of wood. Be sure to purchase the correct Water-repellent preservatives may type of water-repellent preservative. also be used as a treatment for bare Any type of water-repellent preser- wood before priming and painting vative can be used as a natural ex- or in areas where old paint has terior finish by itself, but only some peeled, exposing bare wood, par- are paintable. Manufacturers have ticularly around butt joints or in also developed water-repellent corners. This treatment keeps rain preservatives specifically for exterior or dew from penetrating into the finishes. wood, especially at joints and end Water repellants are also grain, and thus decreases the shrink- available. These are simply water- ing and swelling of wood. As a repellent preservatives with the result, less stress is placed on the preservative left out. Water paint film, and its service life is ex- repellants are not good natural tended (fig. 13). This stability is finishes, but can be used as a achieved by the small amount of stabilizing treatment before priming wax present in water-repellent and painting. preservatives. When dip treated, the Before purchasing and using a wax also decreases the capillary water-repellent preservative or water movement of water up the back repellant, read the label carefully and side of lap or drop siding. The follow the manufacturer’s directions.

A B Figure 13–(A) Window sash and frame treated with a water-repellent preservative and then painted and (B) window sash and frame not treated before painting. Both treatments were weathered for 5 years. Note the nor- mally weathered paint good condition of the wood, and glazing on the treated structure. M119770, M119771

16 Varnishes oil is not recommended for use around the home where people will Varnishes; synthetic resins; and come in contact with it. However, other clear, film-forming finishes wood treated with waterborne salts provide an attractive finish for wood is suggested for use in patio decks, since they allow the natural wood outside steps, privacy fences, and color and grain to show through. other home structures. This material Unfortunately, the durability of is generally light to bright green or these finishes on wood under the brown in color. It can be used out- action of sunlight and moisture is doors without finishing and will re- limited. Regardless of the number of main practically unchanged or coats applied, the film will begin to weather to a light gray. crack and peel, and the finish will have to be completely removed by sanding or with a remover before a new coat is added. In severe exposures, clear film finishes may last barely 1 year. Alternate finishes such as semitransparent stains and water-repellent preser- vatives will give a longer service life and are easier to refinish. Exterior marine or spar varnishes may be used with some success on exterior doors and other areas if adequate protection from the weather is provided.

Preservatives

Wood preservatives are not con- sidered to be finishes. However, wood properly treated with a wood preservative can withstand years of exposure to severe decay and insect attack without being affected. The common wood preservatives fall into three general categories. These are creosote, pentachlorophenol in oil, and the waterborne salt treatments such as chromated cop per arsenate (CCA). Creosote and pentachlorophenol in oil result in a dark and oily surface. Odor with creosote is a problem. Wood that has been pressure treated with creosote or pentachlorophenol in

17 Applying Wood Finishes

Paint swelling and shrinking. They can be applied by brushing or dipping. Lap Proper surface care and prepara- and butt joints and the end of panel tion before applying paint to wood products such as plywood, hard- is essential for good performance. board, and particleboard should be Wood and wood-based products especially well treated since paint should be protected from the normally fails in these areas first weather and wetting both on the (fig. 14). Allow at least 2 warm, job site and after they are installed. sunny days for adequate drying Surface contamination from dirt, oil, before painting the treated surface. and other foreign substances must If the wood has been dip treated, be eliminated. Weather permitting, allow at least 1 week of favorable it is best to paint wood surfaces as weather. soon as possible after installation. 2. After the water-repellent preser- To achieve maximum paint life, vative or water repellant has dried, follow these steps: the bare wood must be primed. 1. Wood siding and trim should Since the primer coat forms a base be treated with a paintable water- for all succeeding paint coats, it is repellent preservative or water very important. For woods with repellant. Water repellants protect water-soluble extractives, such as the wood against the entrance of redwood and cedar, the best rain and dew and thus prevent primers are goodquality oil-base

Figure 14–Paint normally fails first around the ends and edges of a board. Liberal application of a water-repellent preservative can prolong paint life in these areas. M8330013-5

18 and alkyd-base paints. Some latex- (primer and two top coats) is 4 to 6 base primer paints are also designed mils or about the thickness of a for use over these woods. The sheet of newspaper. The quality of primer seals in the extractives so paint is usually, but not always, that they will not bleed through the related to the price. Brush applica- top coat. A primer should be used tion is always superior to roller whether the top coat is an oil-base application. or latex-base paint. For species that are predominately sapwood and Additional Tips on Painting free of extractives, such as pine, a highquality acrylic latex-base paint To avoid future separation be- may be used as both a primer and tween paint coats, the first top coat top coat. Enough primer should be should be applied within 2 weeks applied to obscure the wood grain. after the primer and the second Do not spread the primer too thin. coat within 2 weeks of the first. As Follow the spreading rates recom- certain paints weather, they can mended by the manufacturer. A form a soaplike substance on their primer coat that is uniform and of surface, this may prevent proper the proper thickness will distribute adhesion of new paint coats. If the swelling stresses that develop in more than 2 weeks elapse before wood and thus prevent premature applying another paint coat, scrub paint failure. the old surface with water using a 3. Two coats of good quality bristle brush or sponge. If necessary acrylic latex-base house paint to remove all dirt and deteriorated should be applied over the primer. paint, use a mild detergent. Then If it is not practical to apply two top rinse well with water and allow the coats to the entire house, consider surface to dry before painting. two top coats for fully exposed To avoid temperature blistering, areas on the south and west sides. oil-base paints should not be ap- Areas fully exposed to sunshine and plied on a cool surface that will be rain are the first to deteriorate and heated by the sun within a few therefore should receive two coats. hours. Temperature blistering is On those wood surfaces best suited most common with thick paint for painting, one coat of a good coats of dark colors applied in cool house paint over a properly applied weather. The blisters usually show primer (a conventional two-coat up in the last coat of paint and oc- paint system) should last 4 to 5 cur within a few hours to 1 or 2 years, but two coats can last up to days after painting. They do not 10 years. Thus, three coats of paints contain water. last twice as long as two coats. Oil-base paint may be applied 4. One gallon of paint will cover when the temperature is 40°F. or about 400 feet of surface above. A minimum of 50°F. is area. However, coverage can vary desired for applying latex-base with different paints, application paints. For proper curing of the procedures, and surfaces. Research paint film, the temperature should has indicated that the optimum not drop below 50°F. for at least thickness for the total paint coat 24 hours after paint application.

19 Low temperatures will result in drying out before a logical stopping paint failure. place is reached. Working in the To avoid wrinkling, fading, or loss shade is desirable because the dry- of gloss of oil-base paints and ing rate is slower. One gallon will streaking of latex-base paints, the usually cover about 300 to 400 paint should not be applied in the square feet of smooth surface and evenings of cool spring and fall from 150 to 200 square feet of days when heavy dews form before rough surface. the surface of the paint has For long life with penetrating oil- thoroughly dried. base stain on rough-sawn or weathered lumber, use two coats Solid-Color Stains and apply the second coat before the first is dry. Apply the first coat Solidcolor stains may be applied to a panel or area as you would to to a smooth surface by brush or prevent lap marks. Then work on roller application, but brush applica- another area so that the first coat tion is best. These stains act much can soak into the wood for 20 to like paint. One coat of solid-color 60 minutes. Apply the second coat stain is adequate, but two coats will before the first coat has dried. (If provide better protection and longer the first coat dries completely, it service. will seal the wood surface so that Unlike paint, lap marks may form the second coat cannot penetrate with a solid-color stain. Latex-base into the wood.) About an hour after stains are fast drying and are more applying the second coat, use a likely to show lap marks than the cloth or sponge to wipe off the ex- oil-base ones. To prevent lap marks, cess stain that has not penetrated follow the procedures suggested into the wood. Stain that did not under application of semitransparent penetrate will form an unsightly sur- penetrating stains. Solid-color face film and glossy spots. Avoid in- acrylic latex stains are the most termixing different brands or durable of these finishes. batches of stain. Stir stain thoroughly during application. Semitransparent Penetrating Stains NOTE: Sponges or cloths that are wet with oil-base stain are par- Semitransparent penetrating stains ticularly susceptible to spontaneous may be brushed or rolled on. combustion. To prevent fires, bury Brushing will give better penetration them, immerse them in water, or and performance. These stains are seal them in an airtight container generally thin and runny, so ap- immediately after use. plication can be messy. Lap marks A two-coat wet system on rough will form if stains are improperly wood may last as long as 10 years applied. Lap marks can be in certain exposures. If only one prevented by staining only a small coat of penetrating stain is used on number of boards or a panel at one new wood, its expected life is 2 to time. This method prevents the 4 years, but succeeding coats will front edge of the stained area from last longer.

20 Water-Repellent Preservatives vulnerable to moisture, such as the bottoms of doors and window The most effective method of ap- frames, should not be overlooked. plying a water-repellent preservative One gallon will cover about 250 is to dip the entire board into the square feet of smooth surface or solution. However, brush treatment 150 square feet of rough surface is also effective. When wood is when used by itself. The life expec- treated in place, liberal amounts of tancy is only 1 to 2 years, depend- the solution should be applied to ing upon the wood and exposure. all lap and butt joints, edges and Treatments on rough surfaces are ends of boards, and panels (fig. 15). generally longer lived than those on It is important to apply liberal smooth surfaces. Repeated brush amounts of the solution to the end treatment to the point of refusal will grain of wood. Areas especially enhance durability and performance.

Figure 15–Water-repellent preser- vatives should be applied to all joints before painting. ML835331

21 Refinishing

Paint test for adhesion, firmly press one end of an adhesive bandage onto If you are refinishing an old paint the painted surface. Jerk it off with coat, proper surface preparation is a snapping action, If the tape is free essential if the new coat is to give of paint, it tells you that the latex- the expected performance. First, base paint is well bonded and that scrape away all loose paint. Use the old surface does not need prim- on any remaining paint ing or additional cleaning (fig. 8). If to “feather” the edges smooth with the new latex-base paint adheres to the bare wood. Then scrub any re- the tape, the old surface is too maining old paint with a brush or chalky and needs more cleaning or sponge and water. Rinse the the use of an oil-base primer. scrubbed surface with clean water. Wipe the surface with your hand. If Solid-Color Stains the surface is still dirty or chalky, scrub it again using a detergent. The same technique used to Mildew should be removed with a restore a paint coat can be used for dilute household bleach solution. solid-color stains. Rinse the cleaned surface thoroughly with fresh water and Semitransparent Penetrating Stains allow it to dry before repainting. Areas of exposed wood should be Semitransparent penetrating stains treated with a water-repellent are relatively easy to refinish. Ex- preservative or water repellant, cessive scraping and sanding are allowed to dry for at least 2 days, usually not required. Simply use a and then primed. Top coats can stiff bristle bush to remove all sur- then be applied. face dirt, dust, and loose wood It is particularly important to fibers and then apply a new coat of clean areas protected from sun and stain. The second coat of rain such as porches and side walls penetrating stain often lasts longer protected by overhangs. These areas since it penetrates into small surface tend to collect water soluble checks, which open up as wood materials that interfere with adhe- weathers. sion of the new paint. It is probably adequate to repaint these protected Water-Repellent Preservatives areas every other time the house is painted. Water-repellent preservatives can Latex-base paint can be applied be renewed by a simple cleaning of over freshly primed surfaces and on the old surface with a bristle brush some surfaces where an oil-base and an application of a new coat of paint has already been used and finish. To determine if a water- weathered. Where old surfaces are repellent preservative has lost its ef- to be repainted with latex-base fectiveness, splash a small quantity paint, a simple test should be con- of water against the wood surface. ducted first. After cleaning the sur- If the water beads up and runs off face, repaint a small, inconspicuous the surface, the treatment is still ef- area with latex-base paint and allow fective. If the water soaks in, the it to dry at least overnight. Then, to wood needs to be refinished.

22 Warnings

Refinishing is also required when Do not mix bleach with ammonia the wood surface shows signs of or with any detergents or cleaners graying. containing ammonia! Mixed NOTE: Steel wool and wire together the two are a lethal com- brushes should not be used to clean bination, releasing a gas similar to surfaces to be finished with mustard gas, as well as ammonia semitransparent stains or water- and chlorine gases. In several in- repellent preservatives since small stances people have died from iron deposits may be left behind. breathing the fumes from such a Pentachlorophenol may cause iron mixture. Many household cleaners remaining on the surface to cor- contain ammonia, so be extremely rode. The corrosion products may careful with what types of cleaners then react with certain wood extrac- you mix bleach. tives to form a dark-blue, unsightly Use caution with wood finishes discoloration, which becomes that contain pesticides or preser- sealed beneath the new finishing vatives. When used improperly, system. Pentachlorophenol is pre- they can be injurious to human sent in some semitransparent beings, animals, and plants. For safe penetrating stains and water- and effective usage, follow the repellent preservatives. directions and heed all precautions on the labels. It is advisable to wear unlined protective gloves and to cover nearby plant life when using wood preservatives. Do not use any wood finish containing pen- tachlorophenol indoors. Avoid drift from pesticides ap- plied as a spray. They may con- taminate the surrounding environment. Store finishes containing pesticides in original containers under lock and key-out of reach of children and pets-and away from foodstuffs. Follow recommended practices for the disposal of surplus finishing materials and containers. NOTE: Registrations of pesticides are under constant review by the U.S. Environmental Protection Agency. Use only pesticides that bear a Federal registration number and carry directions for home and garden use. Since the registration of pesticides is under constant review by State and Federal authorities, you should consult with a respons-

23 ible State agency as to the current status of the pesticides discussed in this report.

U.S. GOVERNMENT PRINTING OFFICE: 1983 - 412-523 - 814/280