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| Why should I use Redwood for my project? top |
Use redwood for its long-lasting beauty. No other softwood has the rich beauty or long-lasting performance of redwood. Use redwood for its dimensional stability.
Wood acts like a sponge; when it absorbs moisture it swells and when it loses moisture it shrinks. Redwood (shown below on the left) has thinner cell walls which shrink and swell less than other woods, so redwood is less likely to warp, split, cup or check.
Use redwood for its natural durability. Redwood heartwood is naturally resistant to decay and insects. Use redwood simply because it is a pleasure to use.
Redwood is a favorite with builders because it is lightweight but strong. It is easy to saw, nail and drill. Redwood has little or no messy pitch or resins. Use redwood because it is easy to paint, stain and glue. No other softwood holds paints, stains and other coatings better than redwood. Redwood also bonds exceptionally well.
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| What redwood grade should be used for my deck or fence posts? top |
Use all heartwood grades, such as Construction Heart, for applications on or near the ground. These grades should also be used for deck beams and joists which are within six to twelve inches of the ground.
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| What decking and joist spans should be used when designing my redwood deck? top |
Construction Heart or Construction Common 2x6 decking should be nailed to joists which are spaced no more than 24 inches on center. Joist spans vary according to the dimension used and the joist spacing. For example, typical 2x8 Construction Heart joists spaced 24 inches on center can span 8 feet 9 inches between support beams.
Suggested Joist Spans
Joist Size |
Joist Spacing |
Joist Span |
2x6 |
16 inches on center
24 inches on center
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7 feet 3 inches
6 feet 0 inches |
2x8 |
16 inches on center
24 inches on center
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10 feet 9 inches
8 feet 9 inches |
2x10 |
16 inches on center
24 inches on center
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13 feet 6 inches
11 feet 0 inches |
Extra weight on the deck surface, such as large planters, hot tubs or spas, will require additional support.
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| What can I do to build a deck surface which will look good for a long time? top |
Install decking with the bark side up to minimize grain-raising. Use only one nail per bearing to minimize splitting. Staggered nailing pattern permits slight movement during the wood's natural seasoning process.
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| Can I use redwood and still build an economical deck? top |
There are a whole range of redwood grades that can be used on decks. By carefully choosing the right grade you can save money and build a beautiful project.
The most economical grade for decking is Construction Common. With the strength to do the job, it contains a combination of heartwood and sapwood and will provide years of service.
For posts, beams and joists an all-heartwood grade of redwood is recommended. Construction Heart is the most economical grade for these applications.
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| What redwood grades should I use for a top-of-the-line luxury deck or fence? top |
For a luxury redwood deck or fence, you may want to choose grades that have fewer knots for the visible surfaces. Clear grade or B grade are excellent choices for high-quality decking, posts, rails, trellis work, privacy screens and other highly visible areas.
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| If I specify Clear All Heart redwood, will it always be kiln dried? top |
Not necessarily. The proper specification for any wood product should include more than just the size and grade. The desired moisture content, type of grain (flat or vertical), surface texture (smooth or saw-textured) pattern description and pattern number where applicable, should all be included in the specification
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| Grade rules sometimes refer to "occasional pieces"—what do they mean by that? top |
Occasional pieces means not more than 10% of the pieces in a parcel or shipment. This provision is used primarily to provide for acceptance of minor defects not normally permitted in a grade. These defects, while accidentally overlooked, are not serious enough to justify throwing out the piece when shipping or reinspecting the lumber.
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| Can Clear grade redwood contain knots? top |
Two ¾" or equivalent, sound, tight knots are allowed in occasional pieces of Clear grade redwood. As an example, three one-half inch knots are equivalent to two ¾ inch knots. A single larger knot cannot be substituted for the two ¾ inch knots.
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| Grade descriptions are based upon what dimension of lumber? top |
Unless otherwise specified, grade descriptions are based upon a piece of lumber eight inches wide and twelve feet long. This means that the number of characteristics in larger or smaller pieces may vary in proportion to the size of the piece.
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| What grades of redwood lumber must be grade stamped? top |
Foundation grade and Deck grades are special purpose grades which must be grade stamped.
Foundation grade is selected from two-inch or thicker Construction Heart or better for durability and ability to resist insect and fungus attacks. This grade is typically used for mud sills as an alternative to pressure-treated wood.
Deck Heart and Deck Common are two grades of redwood especially suited for residential or non-residential exterior patio deck uses where specific design values are required in combination with an attractive appearance. These grades are manufactured in 2-inch thickness, in 4- and 6-inch widths. The characteristics and limiting provisions for these grades are essentially the same as those for General Purpose Grades of Construction Heart and Construction Common. The primary difference is the inclusion of slope of grain requirements and knot measurement based upon equivalent displacement rather than average diameter.
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| What makes B grade different from other architectural grades? top |
B Grade is intended for use where only one face and one edge are exposed. Unless otherwise specified, characteristics which do not interfere with the intended use are permitted on the reverse side and other edge. This grade also permits a cutout of not more than one lineal foot in pieces ten feet and longer for removal of defects not otherwise permitted in the grade.
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| What type of nail or fastener should I use to attach decking to joists? top |
Use top quality, corrosion-resistant 16-penny ringed-shank or spiral-shank nails to attach redwood decking. Smooth-shanked nails are likely to result in nail popping if green lumber and/or wet pressure-treated joists are used. Deck screws are also quite popular. Use corrosion-resistant, self-tapping deck screws with bugle heads. They should be manufactured from hardened steel. Electro galvanizing and other methods of zinc coating rarely show the same degree of corrosion resistance as hot-dip galvanizing.
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| Can I use deck clips or other fasteners that hide the nails on my deck? top |
Deck clips are available that work well with redwood decking. With these products you can build a deck without nails showing on the decking surface.
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| What type of nails should I use for redwood siding? top |
Specialty siding nails perform best with redwood or other wood sidings. These nails have smaller sinkerheads with waffling to hold finishes. Siding nails also have thin ringed shanks for extra holding power and blunt tips to reduce splitting. These nails are available in either double, hot-dipped galvanized or stainless steel versions, and they can be ordered to match the color of the siding.
Nails should be long enough to penetrate into combined wood sheathing and framing a minimum of 1-1/2 inches. Siding ¾ inches thick will, therefore, require a 2-1/4 inch (7d) nail. When using non-wood sheathing products, such as foam insulation, longer nails are required.
Extensive studies performed at Virginia Tech University concluded that annularly threaded, stainless steel siding nails with a 3/16-inch diameter checkered, flat, slightly countersunk head, and 1/16-inch blunt diamond point performed most satisfactorily under all conditions commonly encountered.
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| Does a ringed-shank nail really provide more holding power? top |
A ringed-shank nail provides 50 to 100 percent greater holding power than a smooth-shank nail.
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| How long do siding nails have to be? top |
The CRA recommends and the Uniform Building Code now requires that the siding nails be of sufficient length to penetrate 1-1/2 inches into combined solid wood sheathing and framing. So, for example 1/2x6 plain bevel siding over 1/2-inch plywood sheathing and 2x4 framing would require a 2-inch long or 6d nail.
Remember that rigid foam sheathing has no nail-holding power, so these installations require a longer nail. For example, 1x8 T&G siding over 1-inch rigid foam sheathing, 1/2-inch plywood and 2x6 framing would require a 3-1/4-inch or 12d nail.
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| Should I allow for an expansion gap when installing plain bevel siding? top |
Be sure to install kiln-dried rabbeted bevel siding with the required 1/8-inch expansion gap between courses. This will give it room to expand and contract with the humidity.
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| Should I allow for an expansion gap when installing plain bevel siding? top |
Be sure to install kiln-dried rabbeted bevel siding with the required 1/8-inch expansion gap between courses. This will give it room to expand and contract with the humidity.
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| What nails should I use on my redwood interior paneling? top |
Tongue and groove boards up to 8 inches wide should be blind-nailed through the tongue. Nails should penetrate studs or furring strips 3/4 of an inch. Pre-drill nail holes to avoid splitting. Construction mastic may also be used to apply paneling to walls which are in good condition.
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| Do I need to finish exterior redwood? top |
Though redwood will perform better than most other woods if left without a finish, it will look better and last longer if a protective finish is applied and maintained.
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| How do I keep my new redwood siding looking new and natural? top |
Clear water repellent finishes containing mildewcides help preserve the natural appearance of redwood siding. They may not, however, prevent the natural color changes associated with the weathering process. Clear water repellents or water repellent preservatives are the most natural types of finishes, but they are also the least durable. They require reapplication every one to two years. These finishes can be used on decks, fences, siding or other exterior projects.
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| What finish is more durable than clear water repellent but keeps a natural look? top |
Transparent and semitransparent stains may last from three to four years. These finishes contain pigments which protect the wood from the degrading effects of solar radiation.
The best products contain water repellents, mildewcides and ultraviolet light blockers or absorbers. When selecting a pigmented stain, CRA recommends testing finishes on a small area to be sure the desired color effect is achieved. Transparent stains contain less pigment than semitransparent stains and provide a more natural look. These finishes can be used on decks, fences, siding or other exterior projects.
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| How can I get an immediate weathered appearance with a low maintenance finish? top |
Bleaching or weathering stains are available from several manufacturers. These provide a uniform driftwood gray appearance in six to twelve months. Periodic applications of a clear water repellent with mildewcide are recommended after the weathered look is achieved. These finishes can be used on decks, fences, siding or other exterior projects.
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| What finish should I use on my redwood interior? top |
A wide variety of finishes can be used on interior redwood, including the option of using no coating at all. Areas, such as kitchens and baths, which are subject to moisture need the most protective finishes. Alkyd resin or polyurethane sealers and varnishes are appropriate for these areas. Elsewhere, wax finishes, penetrating oils, stains and paints may be used.
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| Are there any special precautions I should take when painting redwood siding? top |
Redwood takes and holds paint better than most woods. It is important, however, to select and correctly apply the right primer.
Use oil- or alkyd-based primers or water-bourne stain-blocking primers on redwood. These primers are available from many paint manufacturers and are formulated especially for redwood, cedar and other wood with a high extractive content.
Follow the manufacturer’s recommendations for application closely. The best finishes will not perform if they are applied incorrectly. High quality acrylic latex top coats provide the best durability.
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| What is back-priming and why is it important that I back-prime my siding? top |
Most manufacturers of solid wood siding and exterior wood finishes recommend back-priming. Back-priming refers to applying a finish to the back of the siding before installation. All edges and ends should be treated as well. Back-priming provides additional insurance against extractive bleeding and dimensional instability or cupping.
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| How can I prepare an existing deck and bring back its color before refinishing? top |
For years the CRA has recommended the tried-and-true method of a preliminary scrub with TSP and household bleach to clean the deck and remove mildew.
To remove stains and restore the natural color, oxalic acid is then applied. Recently, however, many excellent commercially formulated deck cleaners and restorers have become available. These are based upon non-chlorine bleaches, detergents and/or oxalic acid. The manufacturers of these commercial products supply comprehensive directions.
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