Answers to questions most often asked about redwood

By Charles J. Jourdain Vice President of Technical Services California Redwood Association

F ACH year the California Redwood Association's E technical services department gets thousands of phone calls and letters asking for information about redwood. In order of flrequency, siding and deck finishes, color restoration, nailing, specifications and grade description information is most sought.

Redwood sales and counter people are often asked m-any of the same questions. The following is a summary of frequently asked questions and answers.

Q: How do I keep my new redwood siding looking new and natural?

A: Clear water repellent finishes containing mildewcides help preserve the natural appearance ofredwood 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 ro rwo years.

Q: Whar rype of finish water repellent but pearance?

is more durable than clear still retains a natural ap-

A: 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.

Q: How can I achieve an immediate weathered appearance with a low maintenance finish?

A: Bleaching or weathering stains are available from several manufacturers. These provide a silvery 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.

Q: I want to paint my redwood siding. Are there any special precautions I should take?

A: Redwood takes and holds paint better than most woods. It is important, however, to select and correctly apply the right primer. Onty oil or alkydbased stainblocking primers should be used on redwood. These primers are available from many paint manufacturers and are formulated especially for redwood, cedar and other woods 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 have the best durability.

Q: What is back-priming, and is it important that I A: back-prime my siding?

A: Most manufacturers of solid wood siding and exterior wood finishes recommend back-priming. Backpriming 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.

Redwood Special lssue

Specialty siding nails perform best with redwood or other wood sidings. These nails have smaller sinkerheads with waflling 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 l-1/2". Siding 3/4" thick will, therefore, require a2-1/4" (7d) nail. When using non-wood sheathing products, such as foam insulation, longer nails are required.

Q: My redwood deck has remained unfinished for several years. How should I prepare the deck and bring back its color before refinishing?

A: 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.

Story at a Glance

Redwood expert preps sales and counter people on answers to frequent questions proper finishes, nails and grades for projects simplified... current educational materials available.

Q:

What type of nail or fastener should I use for attaching decking to joists?

A: Top quality, corrosion resistant l6-penny ringed shank or spiral shank nails should be used. Smooth shanked nails usually result in nail popping if green lumber and/or wet pressure treated joists are used. Deck screws have also become quite popular. These should have bugle heads, be self-tapping, corrosion resistant and be manufacturered from hardened steel. Electro galvanizing and other methods of zinc coating rarely show the same degree of corrosion resistance as hotdip galvanizing'

Q: Are special nails recommended for applying red- wood siding? How long must the nails be?

Q: lf I specify Clear All Heart redwood, will it be kiln dried?

A: The proper specification of 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.

Q: What decking and joist spans should be used when designing my redwood deck?

A: Construction heart or construction common 2x6 decking should be nailed to joists which are spaced no more than 24" on center. Extra weight on the deck surface such as large planters, hot tubs or spas will require additional support. Typical 2x8 construction heartjoists spaced 24" on center can span 8'9" between support beams. For comprehensive joist and beam span tables, refer to the CRA publication Redwood Deck Construction.

Q: What redwood grade should be u-sed for fence posts or deck structures close to the ground?

A: Only all heartwood grades, such as Construction Heart, should be used for ground contact applications. These grades should also be used for deck beams and joists which are within six to twelve inches of the ground.

CRA's Technical Services Department is available to help answer your customers' questions. CRA also has a selection of booklets on the subjects covered above. which can be used as giveaways or reference pieces'