Decks, Patios, Porches and Docks - Painting Treated Lumber - Front Porch

I've read several posts about painting pressure-treated lumber.

When you say the lumber needs to "weather", do you mean kept indoors or actually left out in the weather?

Seems to me it needs to be kept dry, so I'm thinking keep it out of the rain.

I can leave my plywood slabs on the porch up against the house, where it wouldn't get rained on.

I purchased the lumber a couple weeks ago, and I have some "prep" work to do before nailing down the plywood...

How does this sound? Leave the plywood up against the house out of the rain for another couple weeks - then use Kilz outdoor primer followed by latex?

Thanks!

The main thing is for the PT wood to be dry. Once it is dry use a good exterior oil base primer which can then be top coated with latex.

I'm still not sure how I know it's dry. It seems dry to me. Moisture meters are too expensive (if I were a construction guy I'd want to have one).

So I plan to call the lumber company tomorrow. I guess the question is: How long since the lumber was treated?

Thanks again.

[QUOTE=pilk00] I guess the question is: How long since the lumber was treated?QUOTE]

Yes, I'm sure you have noticed at the lumber yard even when the lumber is kept indoors/under roof sometimes the PT is wetter than others. Dried lumber is also lighter than freshly treated lumber. Unfortunately a moisture meter is the only sure fire way to determine the moisture content. Usually 3-6 months is sufficent drying time.

I think the reason behind the advice you received on letting the treated lumber weather before painting comes from the idea that some of the chemicals the lumber was treated with stayed on the surface, and will come off after a couple of months out in the weather (sun/rain), and if painted, take your paint with it. The advice you got here is more accurate - the real concern is that the lumber be dry. Most of the treated lumber at the big box stores is not dried after treatment, so you have to let it dry.

As far as I know, all PT lumber is treated green. Not only do you have to deal with the lumber's inherent moisture, but you also have the additional moisture added in the treating process.
Dimensional lumber should be installed immediately. If you leave it hanging around waiting for it to dry, you'll end up with a pile of warped and twisted wood.
Install the lumber now and allow it to dry in place for a few months before painting.

Wayne,

Most PT lumber is kiln-dried, then treated. Some is available designated KDAT, that was kiln-dried, pressure treated, then re-dried in the kiln. Most lumber at the big box stores is the first kind, and your advice to install it now or expect it to turn in to a pile of twisted junk was right on target.

I had suspected maybe I hadn't gotten treated lumber - I forgot how green treated lumber looks. I had ordered by phone from a lumber company. I'm sure I told him I wanted treated lumber. I think when I told him I was going to paint the porch, he figured I needed non-treated. I remember him saying to put a lot of paint on it - both sides.

Anyway, today I used a oil-based primer, and tomorrow I'm planning to use a latex finish. Is this a problem? Or can I proceed as planned?

Thanks for the suggestions - I learned some things!

A good oil base wood primer followed by 2 coats of quality latex should give good protection. Depending on how much weather the lumber sees you may need to keep on top of maintinence painting to insure it stays protected.

Thanks, Marksr!

Would you advise 1, 2 or no coats of latex on the underside of the porch surface? I did coat both sides with primer.

pilk00

If this lumber is to be used as a deck/floor I would recomend you use an oil base enamel instead of latex for a top coat. It wouldn't hurt to apply 1 coat of finish to the bottom side and edges.

Had to keep moving - due back at work tomorrow.

I put a coat of premium latex on both sides & around the edges. Too late for oil-based enamel, but I do plan to do the maintenance/repainting you mentioned as needed in the coming months.

For now, will apply a second coat of latex after the lumber's installed.

Thanks for all the help!

Since you started with latex, I would continue with latex. Oil base enamel dries harder = wear longer, but latex has benifits too.