Dimensional Stability Test reports from
Certified Kiln Dried                             the USDA Forest Products Laborato...
Specifying Redwood Siding
Specifying                                                                                   App...
Preventing Moisture Problems
Measuring and Cutting                                                                        ...
Plain Bevel                                      Rabbeted Bevel
Bevel & Rabbeted                             Horizontal Si...
Tongue & Groove                               Tongue and Groove                                 Tongue and Groove
Shiplap &                                     Channel Shiplap                                 V Shiplap
Board & Batten                              Board and Batten
                                            Vertical Siding (...
Redwood Finishes
Apply finishes to clean, dry surfaces only.
The optimum temperature range is
between 50 and 70 d...
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  1. 1. 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 assurance of quality. Redwood is synonymous with quality nail popping. With tighter joints, redwood Redwood grades are established by the architecture. No other siding material provides better siding performance Redwood Inspection Service in the adds value to a home or commercial than other woods. Standard Specifications for Grades of building like redwood. The value of California Redwood Lumber. Properly redwood’s beauty is immediately appar- Finish Retention grademarked lumber will bear the RIS ent and the value of its long-lasting Redwood has an open cellular structure mark. The RIS is the exclusive rules- performance is appreciated for decades. and contains relatively little pitch or writing agency for redwood lumber. resins. This enables redwood to absorb Architects and builders specify redwood and retain all types of finishes better than Quality redwood siding is available in with confidence, knowing that exceptional most other woods. As a result, projects the architectural grades: Clear All Heart, performance is grown into every board look better over a longer period of time. Clear, Heart B and B Grade. and that redwood will add value and Protective finishes last longer and work sales appeal to their projects. Clear All Heart is a superior grade for better. Refinishing is required less often. fine sidings and architectural uses. It is Redwood’s Total Performance Resistance to Decay and Insects all heartwood and the graded face of Redwood’s performance characteristics Redwood heartwood has grown-in each piece is free of knots. are unique among American softwoods. 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.
  2. 2. Specifying Redwood Siding Specifying Application To ensure delivery of the proper siding 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. is necessary to prevent moisture pene- Grain tration into the siding and the wall cavity. Redwood lumber has either flat or vertical For Example Flashing over window and door headers grain. Siding Is considered vertical grain Redwood lumber for 1exterior siding shall and at other horizontal siding breaks when the annual growth rings form an be CRA-RIS grademarked redwood, should be sufficiently sized, well placed, angle of 45 degrees or more with the Heart B grade, 3mixed grain. 4Certified 2 tightly anchored and sealed with caulk- surface of the siding. If the angle is less Kiln Dried, 51x8 channel V shiplap, ing. Thorough caulking of all joints with a than 45 degrees, the siding is known pattern 785R, 7saw-textured face to 6 non-hardening compound is important, as flat grain. Vertical grain siding pos- be exposed. particularly at the butt joints of short sesses enhanced dimensional stability Use Pattern 1 5 length siding laid vertically. High per- and will hold paints and finishes better Grade Pattern Number 2 6 formance caulks such as polyurethane, than flat grain. Grain Texture 3 7 polysulfide or acrylic latex are recom- Seasoning 4 Vertical Grain Flat Grain 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- of vertical siding be coated with water Annual rings Bark side Pith side propriate, and field priming of cut edges. repellent. The use of a drip cap at the Seasoning lower edge of the siding is recommended. Storage and Handling Clear All Heart, Clear, Heart B and B Redwood siding and trim are quality A water repellent building paper, with a Grade sidings are available Certified Kiln finish products and should be handled permeability rating of at least 5 perms, Dried for applications requiring minimal with care. At the job site, redwood siding should be applied over sheathing. This will shrinkage and top performance. should be kept completely under cover help reduce water and wind penetration. Redwood kiln dried to accepted stan- and off the ground. Water-proof cover- dards will include the words “Certified Note: There have been reports of prob- ings should allow air to circulate between Kiln Dried” or the initials “CKD” in the lems arising from the combination of the covering and the siding. Keeping the grademark on each piece or package of wood siding and rigid plastic foam siding clean and dry will help to eliminate siding or be so specified on the invoice. sheathings. CRA advises caution. the possibility of finish problems. For Request Redwood Technical Data Sheet Patterns protection, redwood siding is now avail- Using Redwood Siding Over Rigid Standard redwood siding patterns able wrapped in moisture-proof paper at Foam Sheathing. include: bevel, rabbeted bevel, tongue the sawmill and it should not be un- and groove, shiplap, channel shiplap and wrapped until installation begins. V shiplap. Board and batten siding is Priming laid up using standard size boards. 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.
  3. 3. Preventing Moisture Problems Measuring and Cutting 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. cold exterior. Vapor travels through Stop Moisture Mitered corners, sometimes used with plaster, insulation and wood and may Vapor From Stop Moisture thicker patterns, should be cut in a miter condense into water as it approaches the Inside From Outside box. Plain bevel siding requires a com- colder exterior surfaces of the sidewall. Wallboard Siding pound miter. Predrill nail holes for all This can sometimes result in structural Finished ends, especially mitered ends. damage as well as siding cupping and On All Vapor Barrier Surfaces nail popping. Water entering the siding Using bevel cuts at a 45° angle (see can also cause finishes to blister, peel illustration) can minimize the appearance Insulation and discolor. of gaps if end shrinkage does occur. Vapor barriers are necessary to prevent Sheathing Bevel Cut Siding migration of moisture vapor. They must be applied to the warm side of the stud Building Paper wall, directly under the finish material. There are several types; the most fre- quently used are either plastic or alu- Sheathing Stud minum sheet material with a rating of one perm or less. Those sheets should overlap at least 2 inches at their edges. Ordinary building felt is not a vapor barrier. Do not reduce CRA lap recommenda- Proper interior and exterior wall construction When residing an existing house without tions as this can result in damage from prevents moisture problems. Building paper a vapor barrier, an effective solution can wind-driven water. Carefully observe should have a permeability rating of 5 perms, be to paint the inner side of the exterior expansion clearance requirements for the vapor barrier, a maximum of 1 perm. walls with a vapor barrier paint. the siding pattern selected. Attic areas should be adequately vented Nailing Moisture is the largest cause of siding to prevent vapor from condensing on Nailing recommendations refer to nailing and finish problems. Most problems can cold surfaces or penetrating through the siding to every stud or (for vertical cours- be avoided if precautions are taken ceiling. Critical sources of humidity, such ing) each 2x4 blocking line, at not more during construction. Understanding the as kitchens, baths and laundries, are than 24 inches on center. 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 New energy-efficient construction tech- must be either stainless steel, aluminum floor space. Keep vents free of obstruc- niques increase the amount of humidity or top-quality, domestic, hot-dipped gal- tions. Movement of vapor into stud within homes and commercial buildings. vanized. Electroplated galvanized nails spaces from crawl spaces may take Efficient insulation, storm windows, are not recommended. Poor quality place as water evaporates from the weatherstripping, as well as heating nails will react with redwood’s natural ground under the house, and can be equipment and appliances that retain decay-resisting extractives, and will cause retarded by laying polyethylene film warmth add to the build-up of interior unsightly stains. over the ground. Basements may be a moisture vapor. source of considerable dampness and Nails can be countersunk (not more than This invisible moisture is one of the least require effective ventilation. 1/16 inch) or driven flush with wood sur- understood and most troublesome faces. Unfilled nail holes may not be par- 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.
  4. 4. Plain Bevel Rabbeted Bevel Bevel & Rabbeted Horizontal Siding (Side View) Horizontal Siding (Side View) Bevel Patterns Overlap 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 Stud provides the deepest horizontal shadow Beware of line of all siding patterns. driving nail Sheathing home with Bevel siding is produced in both plain too heavy Nail must a final blow. and rabbeted patterns. Each is available penetrate Wood may in two different butt thicknesses for solid wood split due to 1-1⁄2'' variation in depth of shadow line and non-support in cavity. insulation value. 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. Face nail with one nail only per bearing. Face nail with one nail only per bearing. Rabbeted patterns provide a weather- Drive nail so shank just clears the tip of the Position material to allow expansion tight lap and lay up with greater coverage 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. course should not exceed 1/8 inch. Availability Bevel and rabbeted bevel sidings are edge of the pattern. Nail bevel siding at Surface Feet of Bevel Siding to Cover available in all architectural grades. every stud, which should not exceed 24 1 Square (100 sq. ft.) Plain bevel siding has a smooth surface inches on center. Nominal on one face and a saw-textured surface Width Plain Rabbeted For plain bevel siding, a lap of one inch is on the other face. Either face may be required to ensure weather-tightness. exposed. Rabbeted bevel siding is 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 6 inch 134 117 required in the rabbet. they hold finishes better. 8 inch 124 117 Sample Specification 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 • • •
  5. 5. Tongue & Groove Tongue and Groove Tongue and 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 Sheathing commercial architecture. Tongue and groove siding can be laid up vertically, Stud horizontally or diagonally and is ideal for Sheathing matched interior-exterior combinations. 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 solid wood of the courses. Various design effects penetrate 1-1/2'' solid wood are achievable by alternating patterns 1-1/2'' and board widths. 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 is possible using one 8-penny finishing nail nails per bearing. on both faces. Reversible patterns are per bearing. saw-textured on one face and surfaced smooth on the other. All tongue and groove siding patterns can be special installed between the studs at not more Surface Feet of Tongue & Groove ordered saw-textured. Saw-textured than 24 inches on center. As an alterna- Siding to Cover 1 Square (100 sq. ft.) faces are more even in color and tive, vertical siding may be nailed to 1x3 appearance and they hold finishes better. Nominal Width Coverage Factor furring strips and solid wood sheathing at Tongue and groove redwood is also 4 inch 128 24 inches on center. available in thinner patterns commonly 6 inch 118 used for interior paneling. Sample Specification 8 inch 117 Exterior siding shall be CRA-RIS grade- Installation marked redwood Clear grade, vertical 10 inch 113 Tongue and groove siding is properly grain, Certified Kiln Dried, 1x8 Tongue applied with the groove edge down; this and Groove, pattern 712R, saw-textured assures a weathertight wall. face to be exposed. Horizontally-applied tongue and groove Size Availability siding should be nailed at every stud, Tongue & Groove not exceeding 24 inches on center. Eased Edge S2S-CM Siding applied vertically should be nailed 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 • • • •
  6. 6. Shiplap & Channel Shiplap V Shiplap Vertical Siding (Overhead View) Horizontal Siding (Side View) Channel Shiplap Stud Stud Sheathing Redwood shiplap patterns are widely 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 clearance patterns form strong, deliberate 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 solid wood 1-1/2'' 1-1/2'' only be applied vertically. Availability Shiplap sidings are available in all archi- tectural grades. Standard shiplap siding has a smooth finish on both sides, except those pat- For 6-inch V Shiplap patterns, use one nail Use one nail an inch from the lap for 6-inch terns designated with the suffix R, which per bearing with the nailing point one inch Channel Shiplap. Face nail with two nails per are reversible. Those have a saw-textured from the overlapping edge. For patterns 8 bearing for 8-inch and wider patterns. Space channel pattern on one side and a smooth inches and wider, face nail with two siding nails 1-1/2 inches from edge of overlap and finish V pattern on the other. Shiplap nails per bearing. Position nails one quarter two inches from edge of underlap for 8-inch siding patterns can be special ordered the width of the material in from each edge. boards. Nail wider patterns proportionately. 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 • • •
  7. 7. Board & Batten Board and 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
  8. 8. 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