How to prevent deck boards from cupping?

[Michael Zerance]

A while back I was working on a remodel project that required the removal and re-installation of a few deck boards. I noticed that there were several saw kerfs cut into the bottom of the deck boards along the entire length, I assume to reduce the possibility of cupping. The decking was 2x4, beautifully greyed, and looked great with no cupped or warped boards.

I will be installing 2x4 pressure treated deck boards tomorrow for a small deck I am building and I was wondering if it was worth the time and effort to kerf the bottom face.

Has anyone seen or heard of this before?

[Bradley Gray]

I wouldn't. The best approach to PT is to nail it down as soon as possible.

[Tom M King]

Good luck finding 2x4s fit for decking these days.

[Larry Edgerton]

Look for the heart and orient the heart down. Not always possible as the heart crosses center on some boards but do your best. This will make them prone to have the cup down rather than up.

Me, I refuse to do PT decks any more. Its all Junk!

Larry

[Kevin Bourque]

Me, I refuse to do PT decks any more. Its all Junk!

Larry

I agree, PT is going out of favor now that composites have gotten affordable.

[Brad Adams]

I agree, PT is going out of favor now that composites have gotten affordable.
Obviously you haven't priced composite decking lately. It is far from affodable.

[Rich Engelhardt]

Small deck = perfect place for composite.

[keith micinski]

I hate composite decking but at 2 and a half times the price for a reasonable size deck your talking a few hundred dollars difference. It has way less maintence and is way easier to shovel snow off of.

[Tom M King]

Here at the lake where I live, people are getting away from composite decking. I have some under a big overhang that has held up well on our "dog porch", but others that had it put in the first few years it was available have found that it hasn't held up to the promise of longevity.

I've had the best luck with clear grade 5/4 decking boards by putting single screws on alternating sides of each board on alternating joists. A dock I built like this in 1991 still looks fine with very little cracking, as does a deck in front of our house.

[John McClanahan]

I built a couple of steps using 2x12 PT lumber and made a couple rip cuts in the bottom side like you describe. I just made mine the width of my saw blade. The steps are less than 1 year old, so it's too early to tell if the cuts did any good. It sure didn't hurt anything, though!

I got the idea from some ready made deck steps I saw at Lowes. I figured if those steps had them, there must be a reason.


John

[David Helm]

Putting the heart down does not prevent cupping. The wood dries by the sun forcing the water through to the back side. Cupping will happen regardless of the board orientation. The saw kerfs actually do help.

[Steve Peterson]

Look for the heart and orient the heart down. Not always possible as the heart crosses center on some boards but do your best. This will make them prone to have the cup down rather than up.

Does "heart down" mean that the growth rings on the end will be in a frown position? It seems like this would make the edges curl up. Do the screws prevent this type of cupping, so you are only worried about the center of each board cupping upwards?

Steve

[Mel Fulks]

Agree heart down doesn't prevent cupping ,but it does prevent that razor blade type grain edge lifting up.

[Von Bickley]

Most normal PT lumber will twist, cup, curl and perform all types of movement. My local lumber yard carries Kiln Dried PT Lumber. Looks and works great, but VERY Expensive.....