Dimensional Stability Test reports from Certified Kiln Dried the USDA Forest Products Laboratory show that redwood has less volumetric Siding Patterns and and tangential shrinkage than any other domestic softwood. This means that The CRA trademark is on products of Applications redwood siding will lay flat and straight member mills of the California Redwood throughout the life of the structure with Association only and is an additional minimal warping, cupping, checking and Redwood is synonymous with quality assurance of quality. nail popping. With tighter joints, redwood architecture. No other siding material Redwood grades are established by the provides better siding performance adds value to a home or commercial Redwood Inspection Service in the than other woods. building like redwood. The value of Standard Specifications for Grades of redwood’s beauty is immediately appar- Finish Retention California Redwood Lumber. Properly ent and the value of its long-lasting Redwood has an open cellular structure grademarked lumber will bear the RIS performance is appreciated for decades. and contains relatively little pitch or mark. The RIS is the exclusive rules- Architects and builders specify redwood resins. This enables redwood to absorb writing agency for redwood lumber. with confidence, knowing that exceptional and retain all types of finishes better than Quality redwood siding is available in performance is grown into every board most other woods. As a result, projects the architectural grades: Clear All Heart, and that redwood will add value and look better over a longer period of time. Clear, Heart B and B Grade. sales appeal to their projects. Protective finishes last longer and work better. Refinishing is required less often. Clear All Heart is a superior grade for Redwood’s Total Performance fine sidings and architectural uses. It is Redwood’s performance characteristics Resistance to Decay and Insects all heartwood and the graded face of are unique among American softwoods. Redwood heartwood has grown-in each piece is free of knots. resistance to decay and insects that is Its superior stability is especially suited to Clear is similar in quality to Clear All present throughout the lumber, not just the demands of siding applications. Its Heart, except that it includes sapwood on the surface. Wood exposed through finish retention, weatherability, flame in varying amounts. Some boards may sawing, boring or nailing is as decay- resistance and insulation properties have one or two small, tight knots on resistant as the surface. make it ideal for virtually any project and the graded face. even the most extreme climate. Heart B is an economical all-heartwood grade containing a limited number of tight knots and characteristics not permitted in Clear or Clear All Heart. It is graded on one face and one edge. B Grade is an economical grade con- taining a limited number of tight knots with sapwood accenting the heartwood. Specifying Redwood Siding Specifying To ensure delivery of the proper siding Application product, the specifications should Storage & Handling include: use, grade, grain, seasoning, General Application Information pattern description and number, and Careful attention to construction detailing surface texture. Grain is necessary to prevent moisture pene- Redwood lumber has either flat or vertical For Example tration into the siding and the wall cavity. grain. Siding Is considered vertical grain Redwood lumber for 1exterior siding shall Flashing over window and door headers when the annual growth rings form an be CRA-RIS grademarked redwood, and at other horizontal siding breaks angle of 45 degrees or more with the 2Heart B grade, 3mixed grain. 4Certified should be sufficiently sized, well placed, surface of the siding. If the angle is less Kiln Dried, 51x8 channel V shiplap, tightly anchored and sealed with caulk- than 45 degrees, the siding is known 6pattern 785R, 7saw-textured face to ing. Thorough caulking of all joints with a as flat grain. Vertical grain siding pos- be exposed. non-hardening compound is important, particularly at the butt joints of short sesses enhanced dimensional stability 1Use 5Pattern and will hold paints and finishes better 2 6 length siding laid vertically. High per- Grade Pattern Number formance caulks such as polyurethane, than flat grain. 3Grain 7Texture 4 polysulfide or acrylic latex are recom- Vertical Grain Flat Grain Seasoning mended for best results. In addition, the Installation section of the The lowest edge of siding should be at specification should specify: non-corro- least 6 inches off the ground to prevent sive fastener materials, type and size; moisture problems. It is particularly bearing and fastener spacing require- important that end grain at the bottom ments; water repellent application as ap- Annual rings Bark side Pith side of vertical siding be coated with water propriate, and field priming of cut edges. repellent. The use of a drip cap at the Seasoning lower edge of the siding is recommended. Clear All Heart, Clear, Heart B and B Storage and Handling Grade sidings are available Certified Kiln Redwood siding and trim are quality A water repellent building paper, with a Dried for applications requiring minimal finish products and should be handled permeability rating of at least 5 perms, shrinkage and top performance. with care. At the job site, redwood siding should be applied over sheathing. This will Redwood kiln dried to accepted stan- should be kept completely under cover help reduce water and wind penetration. and off the ground. Water-proof cover- dards will include the words “Certified Note: There have been reports of prob- Kiln Dried” or the initials “CKD” in the ings should allow air to circulate between the covering and the siding. Keeping the lems arising from the combination of grademark on each piece or package of wood siding and rigid plastic foam siding or be so specified on the invoice. siding clean and dry will help to eliminate the possibility of finish problems. For sheathings. CRA advises caution. Patterns protection, redwood siding is now avail- Request Redwood Technical Data Sheet Standard redwood siding patterns able wrapped in moisture-proof paper at Using Redwood Siding Over Rigid include: bevel, rabbeted bevel, tongue the sawmill and it should not be un- Foam Sheathing. and groove, shiplap, channel shiplap and wrapped until installation begins. V shiplap. Board and batten siding is laid up using standard size boards. Priming It is recommended that a water repellent Pattern Numbers containing mildewcide be applied to all Each siding pattern has a pattern num- surfaces of redwood siding before ber. To ensure delivery of the proper construction begins. This will inhibit the product, the pattern number should be movement of moisture as well as mildew included on specifications and invoices. growth, two conditions which can Pattern details are given in CRA’s severely damage a finish coating. When Architectural Guide and Redwood a clear, bleached or semitransparent Pattern Book. finish is to be applied later, a preliminary coat of water repellent will protect Textures against weathering and construction Surfaced sidings have a smooth, planed staining prior to final finishing. For best face, emphasizing the wood’s grain performance, special care should be and color. given to end grain; cut ends should be Saw-textured sidings have resawn faces coated before installation. Redwood providing a rough textured appearance siding should always be back-primed. that holds finishes extremely well. Factory priming or pre-finishing is highly recommended. Measuring and Cutting Preventing Moisture Problems causes of structural and finish failures. It All butt joints must occur over a stud or moves as invisible moisture vapor from solid blocking. Be sure that siding fits the warm interior of the house toward the snugly against corner strips and trim. Stop cold exterior. Vapor travels through Mitered corners, sometimes used with Moisture plaster, insulation and wood and may Stop Moisture Vapor From thicker patterns, should be cut in a miter From Outside Inside condense into water as it approaches the box. Plain bevel siding requires a com- colder exterior surfaces of the sidewall. Siding Wallboard pound miter. Predrill nail holes for all Finished This can sometimes result in structural ends, especially mitered ends. On All damage as well as siding cupping and Surfaces Vapor Barrier nail popping. Water entering the siding Using bevel cuts at a 45¡ angle (see illustration) can minimize the appearance can also cause finishes to blister, peel Insulation and discolor. of gaps if end shrinkage does occur. Vapor barriers are necessary to prevent Bevel Cut Siding Sheathing migration of moisture vapor. They must Building be applied to the warm side of the stud Paper wall, directly under the finish material. There are several types; the most fre- Sheathing quently used are either plastic or alu- Stud minum sheet material with a rating of one perm or less. Those sheets should overlap at least 2 inches at their edges. Do not reduce CRA lap recommenda- Ordinary building felt is not a vapor barrier. tions as this can result in damage from Proper interior and exterior wall construction When residing an existing house without wind-driven water. Carefully observe prevents moisture problems. Building paper a vapor barrier, an effective solution can should have a permeability rating of 5 perms, expansion clearance requirements for the vapor barrier, a maximum of 1 perm. be to paint the inner side of the exterior the siding pattern selected. walls with a vapor barrier paint. Nailing Attic areas should be adequately vented Nailing recommendations refer to nailing Moisture is the largest cause of siding to prevent vapor from condensing on siding to every stud or (for vertical cours- and finish problems. Most problems can cold surfaces or penetrating through the ing) each 2x4 blocking line, at not more be avoided if precautions are taken ceiling. Critical sources of humidity, such than 24 inches on center. during construction. Understanding the as kitchens, baths and laundries, are dynamics of wood’s reaction with mois- best ventilated by fans that exhaust out- Selection of proper nails is important. ture will be the builder’s best protection doors. Crawl spaces should be well Siding nails with annular-ringed shanks against callbacks. ventilated all around the house; the vent provide the best holding power. All nails area should equal about 1/50th of total must be either stainless steel, aluminum New energy-efficient construction tech- niques increase the amount of humidity floor space. Keep vents free of obstruc- or top-quality, domestic, hot-dipped gal- tions. Movement of vapor into stud vanized. Electroplated galvanized nails within homes and commercial buildings. Efficient insulation, storm windows, spaces from crawl spaces may take are not recommended. Poor quality place as water evaporates from the nails will react with redwood’s natural weatherstripping, as well as heating equipment and appliances that retain ground under the house, and can be decay-resisting extractives, and will cause retarded by laying polyethylene film unsightly stains. warmth add to the build-up of interior moisture vapor. over the ground. Basements may be a Nails can be countersunk (not more than source of considerable dampness and 1/16 inch) or driven flush with wood sur- This invisible moisture is one of the least require effective ventilation. faces. Unfilled nail holes may not be par- understood and most troublesome ticularly noticeable where natural finishes are used as long as proper quality nails have been used. At mitered corners, or near the edge or end of a piece, pre-drill the nail hole to avoid splitting the wood. Nails must be long enough to penetrate into studs (or stud and wood sheathing combined) at least 1-1/2 inches. Do not fasten siding to only composition or pressed fiber sheathing as those materi- als provide no nail-holding power. Do not use staples for redwood siding. Staples do not provide adequate holding power and most are not corrosion-resistant. Plain Bevel Rabbeted Bevel Bevel & Rabbeted Horizontal Siding (Side View) Horizontal Siding (Side View) Overlap Bevel Patterns undercourse by 1'' Redwood bevel siding, also known as lap 1⁄8'' Stud expansion or clapboard siding, has the timeless clearance appeal of a strong traditional style and Sheathing provides the deepest horizontal shadow Stud Beware of line of all siding patterns. driving nail Sheathing home with Bevel siding is produced in both plain too heavy and rabbeted patterns. Each is available a final blow. Nail must Wood may penetrate in two different butt thicknesses for split due to solid wood variation in depth of shadow line and non-support 1-1⁄2'' insulation value. in cavity. Plain bevel patterns produce a bolder shadow line than rabbeted bevel pat- Nail clears tip terns of the same thickness. Rabbeted of undercourse bevel, with its 1/2-inch rabbet milled Nail must to fit over the thin edge of the preced- penetrate ing course, allows the siding to lay solid wood 1-1⁄2'' flat against the studs or sheathing. Rabbeted patterns provide a weather- Face nail with one nail only per bearing. Face nail with one nail only per bearing. tight lap and lay up with greater coverage Drive nail so shank just clears the tip of the Position material to allow expansion preceding undercourse. The space between clearance of 1/8 inch. Drive nail about one than plain patterns. the nail shank and the tip of the preceding inch above lower edge of course. Availability course should not exceed 1/8 inch. Bevel and rabbeted bevel sidings are available in all architectural grades. edge of the pattern. Nail bevel siding at Surface Feet of Bevel Siding to Cover Plain bevel siding has a smooth surface every stud, which should not exceed 24 1 Square (100 sq. ft.) on one face and a saw-textured surface inches on center. Nominal on the other face. Either face may be For plain bevel siding, a lap of one inch is Width Plain Rabbeted exposed. Rabbeted bevel siding is required to ensure weather-tightness. 4 inch 160 128 available with either a smooth or saw- Note: With CKD rabbeted bevel patterns, 5 inch 143 textured face. Saw-textured faces are an expansion clearance of 1/8 inch is more even in color and appearance and required in the rabbet. 6 inch 134 117 they hold finishes better. Sample Specification 8 inch 124 117 Installation Exterior siding shall be CRA-RIS grade- 10 inch 122 113 With plain bevel patterns, use a furring marked redwood Clear grade, mixed strip to support the lower edge of the grain, Certified Kiln Dried, 3/4x8 starting course. With rabbeted patterns, Rabbeted Bevel, pattern 372, with a Size Availability the bottom course should be supported saw-textured face. Bevel & Rabbeted Bevel by a nailing strip sawn from the thin Bevel 4'' 5'' 6'' 8'' 10'' 1/2 inch ¥¥¥¥ 3/4 inch ¥¥¥

Rabbeted Bevel S1S-2E smooth 4'' 5'' 6'' 8'' 10'' 1/2 inch ¥¥¥ 3/4 inch ¥¥¥

Rabbeted Bevel S1S-2E saw-textured 4'' 5'' 6'' 8'' 10'' 3/4 inch ¥¥¥ Tongue and Groove Tongue and Groove Tongue & Groove Horizontal Siding (Side View) Horizontal Siding (Side View)

Redwood tongue and groove siding is versatile and weathertight. Its variety Stud of refined patterns has established a permanent place in residential and commercial architecture. Tongue and Sheathing groove siding can be laid up vertically, Stud horizontally or diagonally and is ideal for matched interior-exterior combinations. Sheathing Tongue and groove patterns are pro- Blind nailed duced in square edge, eased (slightly rounded) edge and various widths of V groove edges. The latter create a Nail must shadow line emphasizing the direction penetrate Nail must of the courses. Various design effects solid wood penetrate 1-1/2'' are achievable by alternating patterns solid wood and board widths. 1-1/2'' Availability Tongue and groove sidings are available in all architectural grades. Standard tongue and groove patterns For 4-and 6-inch widths of tongue and groove Tongue and groove siding 8 inches or wider come from the mill with a smooth surface siding over solid wood sheathing, blind nailing should be face-nailed, using two 8-penny on both faces. Reversible patterns are is possible using one 8-penny finishing nail nails per bearing. saw-textured on one face and surfaced per bearing. smooth on the other. All tongue and groove siding patterns can be special ordered saw-textured. Saw-textured installed between the studs at not more Surface Feet of Tongue & Groove faces are more even in color and than 24 inches on center. As an alterna- Siding to Cover 1 Square (100 sq. ft.) appearance and they hold finishes better. tive, vertical siding may be nailed to 1x3 Nominal Width Coverage Factor furring strips and solid wood sheathing at Tongue and groove redwood is also 4 inch 128 available in thinner patterns commonly 24 inches on center. 6 inch 118 used for interior paneling. Sample Specification Installation Exterior siding shall be CRA-RIS grade- 8 inch 117 Tongue and groove siding is properly marked redwood Clear grade, vertical 10 inch 113 applied with the groove edge down; this grain, Certified Kiln Dried, 1x8 Tongue assures a weathertight wall. and Groove, pattern 712R, saw-textured face to be exposed. Horizontally-applied tongue and groove siding should be nailed at every stud, Size Availability not exceeding 24 inches on center. Tongue & Groove Siding applied vertically should be nailed Eased Edge S2S-CM to 2x4 horizontal blocking that is 4'' 6'' 8'' 10'' 1 inch ¥¥¥

V1S S2S 4'' 6'' 8'' 10'' 1 inch ¥¥¥¥

V2S-S1S Saw Textured 1S 4'' 6'' 8'' 10'' 1 inch ¥¥¥¥ Channel Shiplap V Shiplap Shiplap & Vertical Siding (Overhead View) Horizontal Siding (Side View)

Channel Shiplap Stud Stud Redwood shiplap patterns are widely Sheathing Sheathing used for siding and paneling because of the varied visual effects that can be achieved. The boards are self-aligning, 1⁄8'' which makes installation easy. Shiplap expansion patterns form strong, deliberate clearance shadow lines. Shiplap siding in V channel, Cove and Boston shiplap patterns can be applied Nail must either horizontally or vertically. Square- Nail must penetrate edged channel shiplap patterns should penetrate solid wood only be applied vertically. solid wood 1-1/2'' 1-1/2'' Availability Shiplap sidings are available in all archi- tectural grades. Standard shiplap siding has a smooth finish on both sides, except those pat- terns designated with the suffix R, which Use one nail an inch from the lap for 6-inch For 6-inch V Shiplap patterns, use one nail are reversible. Those have a saw-textured Channel Shiplap. Face nail with two nails per per bearing with the nailing point one inch channel pattern on one side and a smooth bearing for 8-inch and wider patterns. Space from the overlapping edge. For patterns 8 finish V pattern on the other. Shiplap nails 1-1/2 inches from edge of overlap and inches and wider, face nail with two siding two inches from edge of underlap for 8-inch nails per bearing. Position nails one quarter siding patterns can be special ordered boards. Nail wider patterns proportionately. the width of the material in from each edge. with a saw-textured face. Saw-textured faces are more even in color and appearance and they hold finishes better. Installation Shiplap sidings applied horizontally start with the bottom course and are nailed at each stud, which should not exceed 24 inches on center. Channel shiplap pat- tern sidings require a 1/8-inch expansion clearance in each joint. Shiplap siding applied in vertical courses should be nailed to 2x4 horizontal blocking that is installed between the studs at not more than 24 inches on center. As an alternative, vertical siding may be nailed to horizontal 1x3 furring strips and solid wood sheathing at 24 inches on center. Sample Specification Exterior siding shall be CRA-RIS grade- marked redwood Clear All Heart grade, mixed grain, Certified Kiln Dried, 1x8 V Shiplap, pattern 794, smooth face. Surface Feet of Shiplap Siding to Cover 1 Square (100 sq.ft.) Nominal Width Coverage Factor 6 inch 124 8 inch 121 10 inch 116

Size Availability Shiplap Patterns 6'' 8'' 10'' 1 inch ¥¥¥ Board and Batten Board & Batten Vertical Siding (Overhead View)

The popular board and batten siding Stud styles are not, strictly speaking, siding patterns but are created using standard Sheathing size lumber. Any number of interesting treatments can be created, including various width battens over wide board, even spaced board and batten, and reverse board and batten. Availability Any clear or tight-knot grade of redwood lumber may be used, either with smooth or saw-textured face. Clear All Heart, Clear, Heart B and B Grade lumber is Nail must available Certified Kiln Dried. penetrate solid wood Installation 1-1/2'' Board and batten patterns should only be applied vertically. Boards should be nailed to horizontal blocking placed not more than 24 inches on center. As an Space underboards at least 1/2 inch apart Board and batten siding can have a variety alternative, 1x3 or greater horizontal and nail with one nail per bearing through the of appearances depending on the width of furring strips may be applied over solid center of the material. For boards wider than boards and battens. A reverse board and wood sheathing. 8'', use two face nails evenly spaced. Wider batten pattern is achieved by placing wide spacing may be used with wider battens. boards over the narrow battens. Sample Specification Nail batten strips through the center so the Exterior siding shall be CRA-RIS grade- nail shank passes through the space. Make marked redwood, B grade, mixed grain, certain the batten laps the underboard at Certified Kiln Dried, 1x10 saw-textured least 1/2 inch on both sides. and 1x2 saw-textured battens.

Board and Batten Siding Thickness Width Nominal Surfaced Nominal Surfaced 2 1-1/2 1 11/16 3 2-1/2 1-1/4 1 4 3-1/2 2 1-1/2 6 5-1/2 8 7-1/4 10 9-1/4 12 11-1/4 Finishes

Redwood Finishes Apply finishes to clean, dry surfaces only. The optimum temperature range is between 50 and 70 degrees Fahrenheit. Saw-textured redwood holds finishes up to twice as long as smooth-surfaced wood.

Siding Finishes for Redwood Description Application Maintenance

Clear Water Repellents with Apply with brush or roller. Two coats Reapplication required after old finish Mildewcide recommended for new wood. Coat sawn has lost its effectiveness. Reapplication Stabilize color at a buckskin tan and let ends, backs and edges before nailing may be required every 18-24 months. the grain and texture show through. siding in place. Minimize the effect of weathering and redwood’s natural darkening.

Bleaching or Weathering Stains Apply with brush or roller. Use one or Bleaching stains provide low mainte- Provide a gray, natural weathered two coats according to directions. nance. Periodic reapplication of clear appearance. Bleaches accelerate the Bleaching action may be aided by water repellent with mildewcide is natural color changes of wood. periodically spraying surfaces with water. recommended.

Semitransparent Stains Apply with brush for best results, roller Color may wear away after weathering. Variety of colors are available in these next best applicator. Two coats usually Refinishing may be necessary every finishes that let the wood grain show required for new wood; follow manu- 2-4 years. Remove loose dirt and old through. Oil-based stains are recom- facturer’s directions. finish with bristle brush before refinishing. mended for best performance.

Solid Body Stains For best results apply with brush. Avoid Color may wear away with age. Available in a variety of opaque colors. drips and lapmarks. Two coats usually Refinishing may be necessary every These finishes obscure the grain and required for new wood; follow manu- 3-5 years. Remove loose dirt and old have an appearance similar to paint. facturer’s directions. finish with bristle brush before refinishing. Latex stains should be applied over a compatible stain-blocking primer.

Paints Apply with brush for best results. Roller Repaint one coat after most of old coat Durable attractive finishes for traditional is next best applicator. One prime coat and has weathered. Avoid creating an ex- exteriors. Paints obscure the grain and two finish coats are recommended. Back- cessively thick paint film. Sand or scrub the texture of the wood. priming required. Use oil- or alkyd-resin with bristle brush to remove old finish base primer and acrylic latex top coat. and dirt. Countersink nails if sanding.

Caution: Varnishes, lacquers and clear film-forming finishes deteriorate rapidly in moisture and sunlight, so they should not be used.

California Redwood Association 405 Enfrente Drive, Suite 200 Redwood—our renewable resource Novato, California 94949 Additional Literature Telephone 415 382-0662 Architectural Guide Toll Free 888 CAL-REDWOOD Redwood Pattern Book Fax 415 382-8531 Grades and Uses www.calredwood.org Exterior Finishes 10/97