Q: I’m building a small deck in the backyard and for cosmetic reasons am painting it rather than finishing the wood. So, being cost-conscious, I am wondering whether using a Douglas fir 2-by-6 versus a con-heart redwood makes sense. The lumber cost is less than half.
A friend said that the redwood really ought to cure 90 days and then be washed with oxalic acid to leach out the tannins so the paint doesn’t peel and crack.
Whichever wood I choose, I was figuring I could buy it, prime it and screw it down prior to applying the top coat. I didn’t factor in any period for curing, and 90 days is a long time (just because I was in the mood to see my creation finished). But it sounds important to let it cure for some time before doing any of that.
A: Cool your jets. Your friend’s right about allowing redwood to cure prior to painting. The same thing applies to fir if you go that route. Moisture levels in lumber must stabilize prior to painting for the paint to successfully adhere to the wood.
Construction-grade lumber has a relatively high moisture level. The wood must acclimatize before you seal the surface with paint. Excess moisture must evaporate to give the paint its best chance to stay on the wood.
Buy the boards, and stack them with sticks between each board to allow air to circulate. We can’t overemphasize the importance of this step, as it allows air to get to all sides of each board. Let the boards cure for two to three months to allow the moisture content to stabilize. If you can stack the boards out of the weather (under a patio or in the garage), that would be best. If that’s not possible, and they get rained on, the curing time will be extended.
When the curing is complete, plan on priming all six sides of each board. Pay special attention to the ends because the end grain is the most susceptible to moisture penetration and the resultant paint peeling. If you don’t precut the decking, you’ll have to prime them once you’ve screwed them to the joists. Speaking of joists, we strongly recommend using pressure-treated material for the framing to inhibit the possibility of rot.
Consider applying two coats of primer to the decking for extra protection. It’s more work, but it will make the job last longer. This is especially important if you choose to go with fir, as it doesn’t take paint quite as well as redwood.
As to the choice between Douglas fir and con-heart redwood, we’d save a buck and go with fir. The extra work involved is offset by the cost savings. We know this is heresy to lumber dealers, but if you select vertical grain fir, cure it properly and prime and paint it thoroughly, it will perform. An added bonus is that fir is harder than redwood and will resist heavy foot traffic and dings a bit better.
Lowe’s and Home Depot will allow you to go through the “stacks” to select boards without charging a premium. Lumberyards allow it also but generally charge a premium for the “select” grade. Look for vertical grain as opposed to the flat grain. It holds paint better. Use good quality primer and deck paint and you’ll get many years of use from your new deck.
An alternative we’d consider for a painted deck is a composite product we saw a couple of years ago at the Pacific Coast Builder’s Conference. Generally, we’re not big fans of composite decking, but a product called CorrectDeck CX caught our eye. It’s a manufactured plastic/wood product and has a paint-like surface that is impervious to staining. Check it out at www.correctdeck.com/products/decking/cx/default.htm.