FAQ's About Exterior Wood Stains

Proper application of exterior wood stains is important in protecting your wooden surfaces and making sure they withstand water and sunlight in all weather conditions. The following comprehensive Q&A’s will assist you in staining exterior floors, siding, and decks.

Q. I have a brand new deck, built of pressure treated wood. My contractor said to wait until next year before I put anything on it. Should I wait?

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A. No! Even pressure treated wood (PTW) will be adversely affected by sunlight and water. The surface wood fibers will degrade, resulting in graying and splintering. With time more serious damage will likely occur; for instance, cracking and warping. Use an exterior floor stain that's specially formulated to penetrate the hard surface of new PTW and protect it from the elements, while affording resistance to mildew.

Q. Recently I used a fairly well-known water sealant on my deck. Although the water beads up, I notice that the deck is turning gray and is splintering. What's wrong?

A. "Water beading" simply indicates the presence of a water repellent additive in your product. Unfortunately, it takes more than surface water repellency to protect your deck from the elements. To really do the job, you'll need to use a product that penetrates the wood cells and encapsulates the wood fibers with a protective resin. Choose a product which will provide your deck with deep-penetrating protection from the damaging effects of the sun's ultraviolet rays, as well as from rain and snow. Also, look for products which provide mildew resistance.

Q. Why do I have to spend time cleaning my siding before staining? Can't you make a product that will stick to anything?

A. Good surface preparation is the first step to any staining project. Even with new wood, the USDA Forest Products Laboratory has found that as little as two weeks' exposure to weather and sunlight will damage the surface fibers and measurably decrease coating adhesion. A previously coated surface generally has some weathered surface fibers as well as loose coating (chalkiness or peeling), dirt, pollen and mildew. Obviously, these are things you don't want to coat. So you have to remove them to get to a clean, stable surface.

Q. I had my house shingled a few years ago in the expectation that it would weather into that smooth gray color that you often see on beautiful homes at Cape Cod. Instead the results have been noticeably uneven. Why?

A. If you allow the siding to weather naturally, without any additional treatment, it is unlikely that you will ever achieve the uniform gray tone you admired. Chances are your siding is experiencing some uneven weathering due to a disproportionate exposure to moisture and sunlight. Fortunately you can buy products which accelerate the weathering process. Applied properly, you can get a uniformed weathered look in 6 - 12 months.

Q. I'm getting ready to stain the siding of my new house. I'm confused by the terms "Solid," "Semi-Transparent" and "Clear." Which product should I use?

A. There's no right answer to this question; it's a matter of personal preference. All stains differ from paint in that they provide color, yet at the same time, allow the wood's character to show. A "solid" product is the most opaque and allows texture, but little grain detail, to be seen. A "semi-transparent" product allows some grain to be seen; a "clear" will show the most grain. Keep in mind that the more transparent the product, the more its color will be affected by the underlying wood; so, variations in wood color will be more obvious with transparent products, as will any natural blemishes such as knots and tannin. Also, opaque products usually last longer because they block out a greater proportion of damaging, ultraviolet rays.
To make your selection, it's best to try some stain samples on the kind of wood you'll be coating.

Q. My new deck is made of redwood. What product should I use on it?

A. With respect to what "look" you want, it's a matter of personal taste as to how much color or opacity you wish to give any deck's wood. Most people with new redwood (or recently cleaned redwood, in good condition) want the wood to look as "natural" as possible, so they choose a "clear" product, with or without color enhancing pigments. In choosing a color read the label carefully; sometimes a product called "redwood" means it's been formulated for redwood; other times it means it's a redwood color.

Q. I want the floor inside my new sunroom to be the same color as the exterior wood siding. Can I use the same stain I used on the exterior?

A. Probably not. First of all, exterior products should never be used in interior or confined spaces, so unless your "sunroom" is no more than a screened-in porch, then you definitely should not use it. Secondly, unless the exterior stain specifically states that it can be used on horizontal, trafficked surfaces, it will not perform well on a floor.
Besides, as noted earlier, a stain's appearance is affected by the underlying wood, so it's doubtful that the stain will "look" the same on flooring as it does on siding. There are many suitable interior stains on the market which can be tinted to match the color you desire.

Q. How can I estimate how much stain I'll need for my exterior siding?

A. The gallons needed for one coat can be estimated as follows:
• Multiply the house perimeter, in feet, by 10
• Multiply this number by the number of stories
• Multiply this number by 0.85 (to deduct doors and windows)
• Divide this number by the stain's stated spread rate (in sq. ft./gal.)
In formula format:
Approximate gallons of stain for one-coat = {House Perimeter (ft.)} x {10 (ft.)} x {# Stories} x {.085} / {Spread Rate (sq. ft./gal.)}
• The actual stain you need will vary according to your structure's actual surface area as well as the texture and porosity of siding. For example, rough sawn wood will use more stain than smooth; bare wood will use more than previously coated; etc.

Q. I'm getting ready to re-do the stain on my house. How many coats will I need?

A. Usually two coats will be needed, but the answer may vary depending upon the condition of the surface and the "look" you're trying to achieve. For example, if the existing topcoat is in good condition, and you're going to restain to the same, or darker color, one coat may suffice. If it's been a few years since you last stained, or if you're going to a lighter (opaque) color, you'll definitely need two coats.

Q. In comparing exterior stains for a major project, I'm finding a wide variation in price between the least and most expensive brands. Does it really make a difference which brand I choose?

A. It certainly can. As with paint, a quality stain will more than pay for itself by its longevity. After all, the labor component of a job - whether you do it yourself or pay someone else - is a much more important "cost" than the materials. A quality stain can last as much as twice as long as a cheap product - that means many more years without a re-do. Also, be sure to compare the spread rates between the higher and lower priced products. You may discover that the "high priced" product has a greater covering capacity than the cheap one and, therefore, isn't really so much more expensive on a square foot basis.

Q. What are the ideal weather conditions for staining?

A. The air temperature should be between 50 degrees and 85 degrees F. The dew point temperature should be five or more degrees lower than the ambient air. Avoid painting in the sun, too (the sun-warmed surface can be 10 to 20 degrees higher than the ambient air). Also, don't stain if it's windy - the stain will dry too fast.
Try to plan your work so that you are always painting in the shade. Stop at least two hours before sunset (due to the danger of condensation).

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