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miamicuse 01-27-2013 12:25 AM

How to stop PT lumber from warping?
 
I am working on some framing and other stuff and I bought 40 pieces of 2x4x8' PT lumber from a local home center. When I bought them I selected each one and they were all straight and nice.

I then moved them into my garage stack them on the floor.

But since I am working by myself and I have to also do electrical and plumbing as I go, I work a little slow.

Three days gone by I looked at the lumber and a good percentage of them have curved/warped to the point I can't use most of them.

Is there a trick to keep them from doing this?

joecaption 01-27-2013 12:29 AM

Nope, nature of the beast, buy more then you need, let them sit in the sun a few days or at least a dry area and return the ones that twist.

Gary in WA 01-27-2013 12:52 AM

Stack them on sleepers or they will absorb moisture from the earth through the slab without a plastic vapor barrier; http://www.greenbuildingadvisor.com/...-building-code

http://www.anthonyforest.com/pdfs/AW...mendations.pdf

Keep them in a conditioned space so they will not absorb moisture from the outside air. As they are stacked tight in the store, the outside facing ones will dry sooner than the inside of pile, you may have mixed them to dry sooner/more with edges/top faces now exposed to outside air. While framing houses, I would cover plate lumber to protect from the sun/weather/wind with black plastic sheeting, never a problem. The moisture content ends very wet (19%) from the p.t. process and dries before/during/after use. If you can use it quickly to lock it in place with fasteners, it helps somewhat. The wider the board, the more it shrinks as it dries, chart on pp 51; http://books.google.com/books?id=iwS...joists&f=false As it shrinks, due to knots, etc., it warps/twists/cups/wains. Check under the stack for wetness from the moisture coming up from the earth/moisture on slab from the wood.

Gary
PS. the sun will dry them at an enhanced rate to change even more, keep them covered as the second link said.

ddawg16 01-27-2013 12:54 AM

Nice to know I'm not the only one who has dealt with that problem......

I guess PT and concrete have two things in common....there are two types....Concrete/PT that has cracked/warped and concrete/PT that will crack/warp.

Hardway 01-27-2013 01:43 AM

I have PT dog ear fence boards. They bend like a banna and pop deck screw. Also PT lumber srinks too!

hand drive 01-27-2013 09:48 AM

pressure treated dry has less warp because it is somewhat dried after pressure treatment. more costly though and not used much for framing etc, but more for rails, decking and facade type building and it is paintable.

miamicuse 01-27-2013 10:37 AM

I guess part of it is I don't have a truck so getting 8', 10' lumber is a pain.

I got a neighbor to help me buy those 40 pieces so I can use them at my own pace.

Now I need to get 6-8 pieces at a time, use them quickly then go get it again when I move to the next part of it.

I kept it inside the garage, no sun, no air conditioning. They just warp like crazy after a day or two.

handyman_20772 01-27-2013 11:56 AM

Use some sleepers (cut off 2x4's) stack your new wood tightly together on top and use some ratcheting tie downs and make a tight bundle. They will still dry out but not as fast and since there is a air space below they won't wick moisture from the concrete.

hand drive 01-27-2013 12:58 PM

Quote:

Originally Posted by miamicuse (Post 1103035)
I guess part of it is I don't have a truck so getting 8', 10' lumber is a pain.

I got a neighbor to help me buy those 40 pieces so I can use them at my own pace.

Now I need to get 6-8 pieces at a time, use them quickly then go get it again when I move to the next part of it.

I kept it inside the garage, no sun, no air conditioning. They just warp like crazy after a day or two.


if the lumber is installed in a freestanding situation then the pt lumber warp will happen regardless if it is while on the pile or on the house. certain conditions will slow the warp or help it have a guided warp but it is the way treated lumber responds to the elements

spaceman spif 01-27-2013 01:04 PM

When I rebuilt my deck I had the same problem. Bought the wood, worked on a few other parts of the deck, grabbed the lumber and wondered where the wooden double helixes came from.

So I tried to make sure I bought the wood either the same day or same weekend I was going to put it up, but as everyone knows, the best laid plans...

Funny thing was I took some boards that severely curled up back to the big box store (rhymes with Schmowes) where I purchased them, and they let me pick replacement boards, no problem!

I ended up putting heavy duty brackets on my wall and stacked the boards on those to keep them off the ground. I also made sure to put the largest, heaviest boards on top to keep pressure on the smaller ones on the bottom.

Good luck!

Daniel Holzman 01-27-2013 01:27 PM

The issue with low cost (read big box store) PT lumber is that the moisture content is typically very high, sometimes 40%, due to the process of treating the lumber, and the fact that the lumber is milled first, treated second. So as the moisture leaves the PT lumber, of course it twists, bends etc., until it reaches ambient moisture content, which varies by region. In New England, ambient MC is about 16-20% in the summer, and somewhat lower in winter.

I do not know of any way to effectively prevent twisting under these conditions. As has been noted, stacking the lumber and letting it air dry before using helps, but does not eliminate the problem. If you purchase relatively dry PT lumber at a lumberyard (typically NOT available at a big box store), you can pick straight pieces, and they will stay relatively straight. You will pay a premium for straight, dry PT lumber, but if you need it, certainly it is worth it.

And if you figure out how to prevent low grade PT lumber from twisting or warping, patent the idea, you will be the next billionaire.

Maintenance 6 01-28-2013 08:11 AM

Most pressure treated lumber is Southern Yellow Pine, which is not particularly stable on a good day. Try buying #1 grade from a real lumber yard instead of the #2 and worse that they sell in the box stores. It's not fool proof, but will help. For fun, I had a 5' piece of PT 2x12 that I left in the sun. After a few days it curled a good inch. Rolled it over and it curled an inch the opposite direction. That's 2 inches of travel and it never did stabilize and it never split.

jlmran 01-28-2013 10:32 PM

Quote:

Originally Posted by Maintenance 6
Most pressure treated lumber is Southern Yellow Pine, which is not particularly stable on a good day.

Most? I've never seen anything PT but pine. Are there other species which are PT? Always believed it had to do with the sapwood/heartwood ratio. Heartwood is more difficult to treat, so pine's high sapwood ratio facilitated PT.

Are there other species which are PT?

Maintenance 6 01-29-2013 02:25 PM

I actually had some pressure treated oak 6x6s here. They didn't twist all up like SYP. I've been told that on the west coast, there are other species that are treated.


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