Should I Dry Treated Lumber before Painting? And for How Long?

**AndyD** · 07-07-2012, 05:13 PM

I was poking around the treated lumber aisle at my local big-box store, and noticed some of the treated deck boards almost felt wet to the touch. These were some of the most damp (and heavy) pieces of lumber I've ever seen.

If I were to drag these boards home for an outdoor project (that I want to paint), I'm assuming I'd want to let the boards dry out some. Big questions is, how long?

**FrankC** · 07-07-2012, 11:33 PM

Andy the answer is probably in the affiliate link you are spamming us with.

**eggcrate** · 07-08-2012, 10:34 AM

It all is relative ... If you chart the relative humidity for about 30 days along with the temperatures measured every hour or so and plot that against the barometric pressure, the 3 axis chart will give you the best time to sit back and enjoy your favorite beverage. When you are finished with the beverage, either get another one or go kick the pile of wet lumber and see if any water squirts out. After about 3 months of this, the wood will be so warped from laying in the sun that you'll need more beverage to get you over the feeling of wasting money on my stupid answer ... it's all relative.

Frank, did I cover everything?

**AndyD** · 07-08-2012, 03:31 PM

Originally Posted by FrankC

Andy the answer is probably in the affiliate link you are spamming us with.

Hmm....I'm confused.
What affiliate link are you talking about? My signature is just like yours...a simple link going back to a website that I own. I'm pretty sure this forum allows that, no?

**FrankC** · 07-08-2012, 03:32 PM

Pretty well Doug, got to give the guy credit he is creative in his spamming.

**Jerry M** · 07-08-2012, 10:54 PM

OK---

I'm going to answer the question as if it were legitimate. I'm not that good at recognizing spammers, and am willing to give AndyD the benefit of the doubt.

You should let the lumber get dry on the surface as a minimum (The drier the better. Give it more time if you can). Then, you can get away with an all-latex painting scheme---the additional moisture will evavorate out through the latex. But do NOT paint with oil, or the additional moisture will blister the paint.

**AndyD** · 07-09-2012, 07:48 AM

Originally Posted by Jerry M

the additional moisture will evavorate out through the latex. But do NOT paint with oil, or the additional moisture will blister the paint.

Thanks, Jerry!
I'm working on a porch (replacing a few rotting boards) that gets a lot of direct sun, so hopefully that will dry out the boards a little quicker -- before I paint them. Or should I let them dry BEFORE I install? I know that other types of wood can shrink during the drying process. Just thought it would be more convenient to put the boards in place and then wait it out.

**GenerationW.W** · 07-09-2012, 05:51 PM

It's typical to install them wet like that, just remember the boards are going to shrink and gap on their own.

**AndyD** · 07-09-2012, 08:23 PM

Originally Posted by GenerationW.W

It's typical to install them wet like that, just remember the boards are going to shrink and gap on their own.

Thanks for the tip!
I was just on another forum, though, and someone mentioned that treated lumber can take forever to dry -- two weeks for kiln-dry boards and up to a couple months for the "green-tag" boards ("dry" meaning the moisture content of the board has somewhat adjusted to the natural climate of a particular region).

So I guess the trick is to build something that doesn't need to be finished right away? I can't imagine people buying and storing lumber in the garage for two months before they use it.

**tkeithharris** · 07-10-2012, 02:38 PM

You can buy your treated lumber 'dried after treatment'. It is called KDAT. The process takes the finished boards and decking back to the moisture content orginally delivered from the milled, after they kiln dried it.

Pressure treating uses water to carry the perservatives into the wood, adding a lot of moisture to the boards.

'Wet' deck boards should be allowed to dry before painting or staining and depending upon the weather and sun exposure this could take weeks. The best test of when it is ready is the tape measure. The finished deck board should be 5.5 inches wide. Wider than that it is swollen with moisture. KDAT decking can be stained or painted right away.

KDAT decking should be spaced as the wood will not shrink over time. Wet decking should be butted tight during installation to allow for the wood to shrink. You also gain an extra level of quality control with KDAT lumber; it is manually handled after Kiln drying and bad pieces are culled. KDAT is more stable, holds nails and screws better and as stated earlier it is ready to be sealed upon installation.

The process was pioneered many decades ago by a company called Cox Industries.