Is there any special prep needed for painting PT wood? I have heard that installed PT needs to be left unpainted for a period of time, after which normal prep and painting can be done – with either oil-based or latex primer/paint. The “air-drying” does not make a lot of sense to me.
Thanks in advance.
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The general consensus that I hear is to wait about a year for the PT to fully dry out. As far as choosing an appropriate paint, I can't help you with that but I'm sure someone here will be able to.
"The general consensus that I hear is to wait about a year for the PT to fully dry out. "Not according to the US Forest Products Lab.They say as soon as soon as the lumber is dry to the touch. Depending on the weather 2 weeks to 2 months.Then use whatever exterior paint and primer that you like.
Like I said.... that's what I hear guys having success with around here. Take it for what it's worth.... never said it was gospel dude.View Image
What BillHartmann said--many web sites say let it dry a couple weeks. I just did a project with PT plywood and primed it with Benjamin Moore Super Spec. The primer is supposed to be more flexible and allow movement without cracking--we'll see. Several people told me tha main thing is if you protect the wood itself from UV and water, it won't be degraded under the finish and thus won't cause the finish to pop off. We'll see about that too! I did like the primer. I used a couple coats because the green of the PT was bleeding through.
As I told another poster though, the stuff I really liked was Cabot's "Clear Solution"--a waterbased finish that penetrated and really seemed to permeate the wood and hardened inside the wood. It comes in colors but is transparent. It does leave a coating on the wood, not like an oil-based stain. I used the Cabot on the deck part of the project.
I come across a lot of rotted wood around the base of exterior doors. I thought replacing the threshold apron, etc., with PT might be a solution. That's why I was wondering about its paintability. A friend of mine is using Azek on his own house to rebuild around a door. That's an expensive route.
I would think replacing the threshold with PT would be a good idea--especially if the old had rotted--I'd rather have paint peel than have the wood rot. For a threshold, I would seriously consider the Cabot. It comes in some nice colors and I think there is even a Cabot that it opaque, as well as one that is translucent. Cabot also comes in oil based. The guy at the paint store said he had poured one of the waterbased Cabots into a baking dish and let it cure and the result was a tough, flexible film that he could not tear, but was stretchy. He poured a lot and said the solidified product was about a quarter inch thick, but it gives you an idea about what it would be like.
Dry to the touch, maybe a little more so. Remove any loose dusting on the surface. Maybe a light sanding. Unless you have an especially long, dry spell the wood won't get dry enough to use an oil based primer. Trapped moisture from the interior of the wood will force the paint film to peel. Use a high quality acrylic primer instead.
Keep in mind that pressure treated lumber is generally fast growth pine. It will split and twist quite a bit which has nothing to do with the paint. But you won't get the appearance of fine woodwork with the coarse grain and movement.
I always use a solid stain made for pressure treated wood it fades instead of peeling and does not require primer.
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Read "Wood Decks" put out by Forrest Products Lab. They did some research and put to rest some previous practices. Don't wait long to finish. Also paint is not a good choice for treated lumber. The paint film will break off. They reccomend a non film forming finish like a stain. There are stains specially formulated for PT lumber.
Thanks guys. It looks like I'll have to rethink using PT for any kind of trim work that is to be painted. I will try the Cabots on the exterior oak thresholds on my house though.