Question: We live in a bungalow condo and are responsible for maintaining our front and back wooden decks, which are pressure-treated, 2x6 boards with rounded corners. What I have done over a period of 12 years is apply two coats, every two years, of oil-based stain on both decks with no problems. Four years ago, I decided to change this and applied two coats of a water-based product, which I was told by a retailer you could apply over the oil-based product and it would work just as well, and of course, was easier to use.
It worked beautifully on the front deck facing west, which is continually kept clean during the winter by the condo contractor using a leaf blower after each snowfall. However, the back deck is the owner’s responsibility, and because it is not used during the winter, it is difficult to access from either inside the unit, or from outside due to the snow.
After the first two years of using the water-based product, the back deck was fine and didn’t need restaining. However, the last two years, we’ve had mid-winter melting, creating ice that sits on the surface of the deck until the spring. After the first year, I noticed the finish on the deck was starting to come off; after the last winter, about half of the finish was off on the deck. Now the surface is a mess, and I’m unsure about the proper way to refinish it. One person suggested taking the boards off and replacing them. I don’t want to do that unless I have to, because the builder used nails instead of screws.
As another option, I’m wondering if I could use something like a belt sander to remove the finish, well enough to re-stain the flooring with the oil-based product. I’m thinking that the water-based product doesn’t tolerate the ice sitting on it. In my opinion, I don’t think a floor sander would work, as some boards are bevelled and you’d have to grind the boards on the edges, which probably wouldn’t give the same results as a belt sander.
I would really appreciate any information or suggestions you may have to refinish the deck surface.
— Thank you very much, Jim M.
Answer: Refinishing an older deck is always a challenge, as most products will wear off with regular foot traffic, sun and precipitation. Minimal effort should be put toward this because it is purely cosmetic and will require refinishing on a regular basis, no matter what.
Before addressing your concern, the first question I have to ask is: why did you bother staining it in the first place? Pressure-treated wood is manufactured with a process that does not require additional treatment to prevent moisture and insect damage. That is the beauty of this excellent wood product. Most types that are an imitation-cedar colour, like your deck, will have the preservative injected into the wood under pressure, with a brown stain added to cover up the greenish colour of the treatment. This forces the chemicals deeper into the wood fibres than most stains, which typically penetrate just below the surface. Because of this, the treated wood lasts up to five times longer than a typical wood stain, especially on horizontal decking.
I will offer an educated guess for the answer to my question, on your behalf. You wanted to improve the cosmetic appearance of the decking due to fading of the brown colour, over time. This is a typical phenomenon, and unfortunate reality, because the tinted portion of the product is similar to any exterior wood stain in its longevity. After a few years, the brown fades and the resulting light greenish-grey wood remains. Many homeowners don’t like this look and do exactly what you have done: paint a surface coat of stain overtop. As you have stated, this will last one to two years before reapplication is required.
Unfortunately, this will not change no matter what type of finish is used. Whether it is alkyd (oil-based), latex (water-based), or a hybrid product, it will deteriorate primarily due to human traffic. Quite simply, the coloured portion of the stain rubs off on your shoes and boots. The only reason that the oil-based stains last a little longer is that they may penetrate the surface of the wood deeper than latex finishes.
To answer your question more directly, I would not do anything to the surface of the deck prior to refinishing, because you are wasting your time. Also, sanding or excessive scraping of the top of the decking may allow moisture to more easily penetrate the wood, limiting the effectiveness of the pressure-treating preservative. The one piece of advice I can offer is to use a single coat only of alkyd, semi-transparent stain if you are dead set on doing this purely cosmetic task. Using a solid-colour, latex stain, or even a second coat of semi-transparent finish will only minimize the time it takes for it to wear off on your footwear.
Refinishing pressure-treated wood, especially on a horizontal deck surface, may be an exercise in futility. Sanding, or other modifications to the treated wood, may only make the problem worse in the future, and may affect the longevity of this durable product.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.