Pressure Treated Decking Lumber

[Ken Krawford]

I'm going to be replacing the decking on my daughter's deck. It currently has pressure treated 5/4" decking and will be replacing with the same. When picking out boards at the "Big Box" retailers, is there a way to examine a given board to determine its likelihood of warping, twisting, cupping etc. as it dries out? Does the end grain pattern provide any clues?
The deck is 16 ft long with 12 ft joists. I'd like to buy 16 ft boards but transporting will be a bit of a problem. I'm concerned about the joints using two 8 ft boards per row. Am I overthinking it?
BTW, I called a couple of places to price kiln dried PT boards and they were quadruple what HD charges for the "wet" stuff !

[Lee Schierer]

There really isn't a way to prevent deck boards from doing any or all of the things you listed, except to use one of the non-food decking products. the problem stems from the fact that wood will absorb water and when the sun comes out, the top surfaces get baked and dried out while the under side stays damp. You can reduce the cupping by placing the bark side up.

[roger wiegand]

Get KDAT lumber (kiln dried after treatment) from a real lumberyard. If it's going to warp, to a considerable extent, it will already have done it. They will deliver it to you. Much lighter and easier to work with as well, more predictable gaps between boards after it equilibrates.

[Ken Krawford]

I could only find KDAT at 2 yards and they wanted $45 / 16' stick vs $11 at HD. Add $100 delivery charge and I think I'd be better off tossing the ones that are ugly after drying.


Get KDAT lumber (kiln dried after treatment) from a real lumberyard. If it's going to warp, to a considerable extent, it will already have done it. They will deliver it to you. Much lighter and easier to work with as well, more predictable gaps between boards after it equilibrates.

[jack duren]

Just double up joints were needed and split the 16’. Criss cross

I ran into the same problem buying too long of boards needed. When done I ran a belt sander across the seams and slick as ———

[Dave Sabo]

Shorter boards stand a better chance of staying straighter.

KDAT is not a magic bullet for lumber staying straight , flat ect... It GREATLY increases the odds , but it's not a guarantee.

Butt joints (w/8ft.) is an aesthetic issue more than an engineering one. Be sure to re-treat any / ALL cut ends before installing and use joist tape to protect the framing.

[Zachary Hoyt]

Last year I rebuilt the south porch and added a north porch here to replace one that had been torn off more than 50 years ago. The house is 16 feet wide so the porches are too, and I bought 16' lumber from a local lumberyard chain. They delivered for $50 from about 35 miles away, and I was buying a lot more than I could get in one trip on my little trailer. I like the full length pieces, and I find that if I put two screws in each joist, and the joists are 16" on center the boards stay quite flat enough to feel flat when walking across them.

[Bill Howatt]

When I did my deck, where a joint in the deck boards was needed I doubled the joists such that they were not tight together and the deck boards slightly over-hanged the joists with a gap between them. Idea was to avoid the major cause of rot which is moisture collection and not being able to dry out; the end grain is more of a problem. Modern PT is not as anti-rot effective as the old PT.

[Maurice Mcmurry]

If the budget allows think about using Trex or one of the composites. Trex stays looking good for many years and never needs to be stained. Another thing that prolongs the life of a deck is to cover the top of the joists with joist tape. Flashing along the rim at the house is also important.
I remove the old decking by cutting it all up in place rather than trying to take up whole boards.

516119

[Bruce Wrenn]

Doesn't your HD rent trucks? Buy longer boards and haul them in rented truck. As far as cupping, generally longer boards are cut from lower section of tree, which have less knots and less prone to cupping.

[Bill Dufour]

Climate? For something like this I try to buy the wood in summer about one month before the project starts. Stack and sticker it to dry a bit. Buy 10% more then needed. Return badly warped and twisted lumber to the store.
Bill D

[George Yetka]

Im all for trex but it will increase the budget. Make sure you crown your boards so that if it does anything it will have to warp past dead flat before warping. This also will allow water to run off. And as always avoid big box wood.

[Tom M King]

Just look at the grain and leave the ones where the grain runs back and forth across the top. I do the same when picking any lumber for framing or anything else. If the grain looks like a dogs hind leg on top of the board, that one is going to move.

I've built decks and docks using that 5/4 treated lumber. With joists on 16" centers, I alternate the screws from one side to the other on alternate joists. If any of the ends start to twist up after a month or two, those get another screw before it completely dries.

I like the Deckmate screws with T25 heads.

When I was building new houses, I used to order a whole bundle of No.1 grade decking boards. No one ever kept that in stock, but it was available if you bought a whole bundle.

[Bill Howatt]

I'll second Maurice's recommendation of joist tape - I wish I'd used it when I built my deck about 20 years ago but so far so good anyway. I also used Trex decking which like the rest has been down the 20 years; it's faded but otherwise still in great physical condition. Both the cedar and PT previous decking was shorter lived and the Trex is still going.
I've heard of people using roofing ice-guard type product cut into strips for covering joist tops.

[Edward Weber]

Climate is the most impostant IMO
Where are you and the deck located.

[Ken Krawford]

The longest flatbed truck my HD has is 10'. That would leave a 6' overhang which makes me uncomfortable. The longest box truck is 12' but I don't know if it can be driven with the doors open.


Doesn't your HD rent trucks? Buy longer boards and haul them in rented truck. As far as cupping, generally longer boards are cut from lower section of tree, which have less knots and less prone to cupping.

[Ken Krawford]

If it were my deck I'd consider composite but it's for my daughter's house. FWIW, composite is about 4 times the cost of pressure treated at Lowes & Home Depot.


Im all for trex but it will increase the budget. Make sure you crown your boards so that if it does anything it will have to warp past dead flat before warping. This also will allow water to run off. And as always avoid big box wood.

[Ken Krawford]

RE: doubling the joists at joints, could a 2x4 just be sistered to the existing joist since all you're looking for is a sure to screw the deck board into?
Not sure about joist tape. This deck is 22 yrs old. I'll see what kind of shape the joists are in when the decking is torn off.

[Ron Citerone]

I am redoing my 15’ deck top this spring. I am replacing them with 16 boards as I don’t want seams. If I was going the seam route I would alternate 6’ and 8’ so the seam is staggered.

I would double the joist at the seam. My 2 cents.

[Jim Becker]

A utility trailer might be a good way to get the longer material home...one that's an open flat bed so you can have overhang both front and back. That's how I carry long lumber on my 5x8 utility trailer, keeping it toward the centerline where I have more length available. That said, with a deck that long, I'd likely pay for delivery so that the "purveyor of fine pressure treated material" can place it near the work area with a Moffett forklift to cut down on the handling. That's a lesson I've learned over time...where the "line" is between doing the grunt work myself and paying a little to have someone else do it. Deliveries of larger quantities of stuff come under the latter.

[Bill Dufour]

FWIW, composite is about 4 times the cost of pressure treated at Lowes & Home Depot.


And if you use composites you will have to about double the number of joists as well.
Bill D

[Lee Schierer]

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And if you use composites you will have to about double the number of joists as well.
Bill D

Unless your joists are spaced farther apart than 16" centers no additional joists should be required. However, if you decide to put the the decking on a diagonal, then the spacing would need to be a maximum of 12" centers.

[Tom M King]

I built this dock in 1991 with one of my spec houses. The squares are 16' for the 32' square main part. I think it was in 2012 when the boards were turned over because the tops were getting splits in them, but the underside was still good. I think only about 8 boards needed to be replaced. This was a 16" centers frame with screws alternating sides of the boards from one joist to the next. This came out of a bundle of no.1 decking boards.

A few years ago they put that thick rubber like coating on it, and it's still in use.

[Ken Krawford]

I'm in the Atlanta, GA area.


Climate is the most impostant IMO
Where are you and the deck located.

[Earl McLain]

Redid my deck last spring, used Menard's thick decking--pretty consistent 1 1/8" thick. For a 30' wide deck, i ordered all 16' lumber and happily had them deliver-delivery cost was around $110, and i'm about 15 miles from the store. Didn't have a single board that wasn't usable--some warp but at 16' it's easier to "convince" to a good gap than 8',or 10' would be. Cupping was minimal, an i laid all with cup up (end grain "frowning"). I don't know if Menard's has stores in your area, if not i'd sure look around for the thick decking. Price for me was even with Lowe's standard 5/4 decking. Local lumber yard was 2x the money--i'd have liked to support them, but not at the spread we had!!

Used Camo edge screws, and they recommend no screws within 1" of the end, so i doubled joists where the joints fell--probably could have used sistered 2 x 4's next to the 2 x8's, instead i just doubled up the joists, and used double hangers. Hardest part was remembering to put the edge of the doubled joist on the 16" mark--instead of centering that joist (really--remembering to put the double hangers in the right places!! the joists drop into the hanger pockets)

Now that we're seeing spring and some wild temp swings (54 degrees in 12 hours a few days ago--i'm pleased with how flat the whole thing is. Used Kreg blind screws on a smaller (12' x 8') deck about 8 years ago and those are still flat as well. Kreg's were a bit more expensive than Camo for the big deck, plus really need to be pre-drilled where the Camo's were jig & drive with no drilling. HUGE time difference with no drilling and purchased direct from Camo (through Amazon), they shipped quick.

[Ken Krawford]

The Camo screws are an interesting option. I had considered Trex type fasteners and cutting a slot on the edge of the board but the Camo option is considerable cheaper.

[Thomas L Carpenter]

Joist tape is new to me. Haven't built a deck in nearly 30 years. What's it's purpose?

[Bill Howatt]

Joist tape is new to me. Haven't built a deck in nearly 30 years. What's it's purpose?

For decks it goes over the top of the joist and the decking board is fastened on top of it. It is exposed in the gap between boards but is usually an unnoticeable dark color. It keeps the rain water from collecting between the boards and thus reduces rotting. It can also be used for other areas such as wood/flashing interfaces. As I said in an earlier post, I've heard of cutting strips of roof ice-guard material and using it. Probably a very similar product.