Finishing Concepts

Western Red Cedar is a versatile and practical product for finishing, both indoors and out. A wide range of effects are possible with the various stains, bleaches and paints this wood accepts so well-largely due to its freedom from pitch, dimensional stability and fine grain-characteristics which help ensure a minimum of maintenance and long lasting results.

Built-in resistance to decay gives Western Red Cedar a durability that is extended even further by careful application of stains or paints. They enhance longer wood life and provide a maintainable surface in the color tone desired. The wood's dimensional stability helps to prevent paint cracking caused by shrinkage and swelling of the siding, thus extending the finish life.

Finishing Western Red Cedar is easy if one starts with the right materials. For best results, purchase the better grades of finishes and select the best tools. Quality finishes may cost more initially, but their longer service life makes them more economical in the long run.

A Guide to Exterior Finishing

While Western Red Cedar can be left unfinished to a soft silver grey (dependent on weather and exposure conditions), finishes are recommended to provide a uniform, cleanable surface, or perhaps to modify it to a preferred color tone for architectural purposes.

Western Red Cedar is a natural for all exterior finishes. Its built-in resistance to decay and dimensional stability ensure years of trouble-free service and lasting good looks.

When selecting and applying a finish for use on surfaces exposed to adverse moisture conditions, use a finish with a fungicidal additive which will eliminate or reduce discoloration caused by mildew growth.

Stains

Most people are attracted to exterior wood finishes that help retain as "natural" an appearance as possible. More and more semi-transparent finishes on the market have approached this ideal and most also include bonus ingredients of water-repellency additives and mildew inhibitors.

There are two types of natural wood finishes: film-forming and penetrating. Film-forming finishes such as varnishes and urethanes do not penetrate the wood and are to be avoided for exterior application. They lack the permanence needed to extend the life of the wood, and must be refinished again in a year or two. Because film-forming finishes do not penetrate the wood, they prevent the release of moisture within the wood, which results in cracks and blisters.

Latex Stains

Latex stains do not penetrate the wood surface and tend to perform like thin paints. They do however have some porosity which allows limited moisture movement with the wood underneath, providing more stability between the stain and the substrate. The shorter service life of these non-penetrating finishes can be improved with the use of a stain resistant primer.

Latex stains are available in a wide range of colors and allow easy cleanup with water.

Advantages of Penetrating Stains

Natural appearance and protection from moisture are advantages provided by penetrating stains. Since the stains penetrate the wood, there is no peeling or blistering as commonly seen in painted exteriors. Stains perform well on many types of wood with unusual characteristics, including knots, texture and siding that's exposed to severe weather conditions. Most stains contain water repellents and in many cases rot and mildew inhibitors. Penetrating stains come in three types: transparent, semi-transparent and opaque.

Transparent stains contain no pigments but have water-repellent features that protect the wood without hiding the natural coloration, and slow the natural color change process.

Semi-transparent stains, because of the added pigment, are less "natural", but equally beautiful. They modify the original wood color and to a lesser degree the characteristics of the wood, such as grain and knots-but not enough to take away from the overall impact of the wood's natural qualities. Semi-transparent stains are much more durable than transparent stains.

Opaque stains are high in pigment content and thoroughly hide the grain and color of the wood. The surface texture is retained, but these opaque stains tend to perform like paint, and do not penetrate the wood so deeply.

Application

All stains should be applied over clean, dry surfaces so, for best results, use a stiff bristle brush to remove any surface dirt, dust and loose fibers.

Stains are best applied by brush for maximum penetration (natural bristle brushes for oil-based stains, synthetic brushes for water-based stains). For a uniform covering, mix the stain thoroughly before and during applications. Brush stain continuously in patches of workable proportions, always leaving a wet edge to prevent lap marks. For vertical siding, begin at the top of several boards and continue all the way to the bottom. For horizontal applications start at one corner and work to an obvious stop.

For smooth surfaces that are not too absorptive, two coats of stain are not recommended because the second coat won't penetrate and may result in uneven glossy spots. On smoothly-planed wood surfaces a one coat application will last about three years. Rough-sawn and weathered surfaces are much more absorptive and are finished best with two coats of penetrating stain, which should last eight to ten years, providing the second coat is applied within one hour of the first so they both penetrate the surface. Stain that has not penetrated after an hour should be wiped off, for a uniform look.

Bleaches

A uniform weathered effect can be achieved in several months with special bleaching agents available from most leading manufacturers-but use this method on new wood only; it's particularly effective on rough-sawn or saw-textured cedar. Use a brush and apply one or two coats. A water-repellent or transparent penetrating stain can be applied in one or two seasons after the bleaching agent has achieved the desired greying. Note: A similar effect can be simulated with a grey pigmented stain.

Wood Preservatives

A water-repellent preservative can be the only treatment on the exterior if you wish to retain the natural look of Western Red Cedar. Two coats are recommended if this result is desired, however frequent renewal applications may be required depending on climate and exposure conditions.

Paints

If you plan to paint the exterior, then ideally, a water-repellent preservative is best applied to the bare wood before the siding is installed. Butt joints and wood laps should receive special attention as well as other potential spots where water might seep in. After the water-repellent has thoroughly dried, the bare wood is primed, again, preferably prior to siding application. Since the primer is the base for all subsequent painting, it must be applied carefully. For Western Red Cedar siding, either an oil-based or alkyd-based primer is best. Some latex based primers are also designed to go over cedar. Enough primer should be applied to obscure the wood grain.

Two topcoats are applied over the primer. If it is not practical to double-coat the entire house, then consider two coats on the south and west sides, because they weather more quickly.

There are three types of paints to choose from: oil, oil alkyd or all-acrylic latex. All-acrylic latex paints are easy to use and very easy to clean up with water afterwards, with no potential risk of fire hazard from oily rags, thinners, etc. Most professionals and do-it yourselfers prefer it. Oil adheres better, but preparation and cleanup discourages many. Oil alkyd is faster drying, but presents the same problems as oil.

Painting Exteriors

New Wood: Paint as soon as possible after the siding is installed. Use non-corrosive fasteners such as hot-dipped galvanized, aluminum or stainless steel to prevent streaking and ruining the finish. Use a dry brush to remove dust, particles of wood and other foreign matter before you paint. Seal all cracks around doors and windows, and wherever wood comes together, with caulking compound to prevent moisture problems.

To minimize moisture problems, we recommend that fans be installed in kitchens, bath and laundry rooms. Attics should be ventilated, crawl spaces covered with 3 or 4 mil polyethylene film and the area properly vented. During the building stage, it's wise to install vapor barriers behind the inside walls in those rooms that create the most moisture, to prevent paint blistering and peeling to the exterior walls.

The novice painter would be well-served to first paint the exterior wall on the most secluded side of the house. Start with the siding, and paint with the grain. Don't paint in the direct sunlight. Next paint the inner trim of the window and move outward. All other trim is done last.

Old Wood: If the exterior walls are severely blistered or peeling, you may have a serious moisture problem that must be solved. Exhaust fans, attic louvers or fans, vented holes or wedge vents and caulking may be necessary before repainting. Alligatoring will require power sanding down to the bare wood, then priming and painting. Chalking can be removed by washing. Mildew can be treated with a good wash-down, using household detergent then mixing bleach with water and letting it sit on the affected area for a few minutes before rinsing off.

WARNING: Never mix bleach with cleaning solutions containing ammonia. It's extremely dangerous to your health.

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Last modified: August 28, 2014