Question on wood warping...Deck boards

Re: Question on wood warping...Deck boards

I was taught the end grain should be in the "frowning" orientation. When the wood gains moisture the tangential swelling is greater than the radial swelling, so the board cups on the underside and rain runs off the top.

"Bark Side UP"

Re: Question on wood warping...Deck boards

Flat sawn wood cups away from the heart when it shrinks. This said, there are a ton of variables going on in a deck, like wood species, climate conditions, ambient MC, grain orientation, method of application, etc.. Short story is, I wouldn't worry too much about it. We have a lot of decking around our house, probably a thousand sq. ft. of 1 1/2" yellow cedar, of varying grain orientations, and all the boards have stayed pretty flat for the most part since they were laid in 2016. We used Camo toe-screws, which hold both sides of the board down, relatively invisibly. That outfit also sells some pretty cool cam jacks and clips for grooved decking that you might look into.

Ellis

Re: Question on wood warping...Deck boards

To confuse matters even more, some decking have both smiles and frowns in the same board. Just depends which end you're looking at.

Re: Question on wood warping...Deck boards

Ellis - doesn't your response contradict the "frowning" and "bark side up" responses above?

I've seen decks from both sides Now...

You are right, the last time I put decking on my deck many of the boards were one way one one end and the other way on the other.  My effort here is to take your best shot.  My friend bought deck boards that are KDAT (Kiln Dried After Treatment) and it will be interesting to see if that has much effect.  Sure does make them lighter and easier to handle and eliminates the shrinking of the boards changing the spacing.

Re: Question on wood warping...Deck boards

Yes, Pat. I've also heard the bark-side-up advice and I take it with a grain of salt because of the other variables. In my experience, deck boards are more likely to shrink over time, and shrinkage on frowny flat-sawn lumber is going to cup the board upwards. My point is that securing both edges goes a long way to keeping things flat, not to mention that there is going to be variability in the ring patterns in any given pile of wood. You aren't going to find a perfect strategy. For me, it's not worth the effort to try to decipher each board.

Ellis

Re: I've seen decks from both sides Now...

I can see how some sort of drying would be a benefit, if for no other reason than keeping the shrinkage down. Remember, though, that the wood is going to eventually settle out at whatever average outdoor MC is in your area. If it's too dry, it will expand, and you need to be sure you take that into account.

Ellis

Re: Question on wood warping...Deck boards

The ideal decking is not out there anymore. You can attempt to retain what you have as long as possible (25 years) but most decks will start failing around 20. [I expect the forum woodwork to explode with contrarian testimonies, but....] Undercarriages need to be the best pressure treated joists you can obtain and spaced at the conservative side of the framing tables. I would add tape to the top surfaces of the joists.

The best decking in my local Western Red Cedar is vertical grain. It survives the longest and resists splitting. I won't use flooring wider than 4" nominal due to sap wood condition. We find treated softwood (SYP, Pines, Firs)  to split and shake too soon. The alternative, plastics, are cosmetically better, if more expensive. Orientation (smiley vs frown) is more dependant on surface appearance. Heartwood is more durable in exposure.  Also, a 4" exposure is least problematic.

An attachment system such as Camo, using unexposed side entry, leaves only wood to catch an observer's eye. It's sympathetic to aligning bent boards during installation. The depressed hardware allows annual aggressive chemical and powerwash stripping to continue for the life of the wood. The Camo screws are fond of sliding through the tool, especially when decking diagonally to the joists. I gave up on using finishes.

In my professional experience inorganic paving on rock subbase is the the most durable and economical.

Re: Question on wood warping...Deck boards

Good advice, Bruce. Some flatsawn woods can be downright dangerous when laid heart-side up, notably cypress. Central wafers of raggedy flat grain will separate and leave knifelike slivers that can really ruin your day. This is one reason to install bark-side up (and not to use flat-sawn cypress for outside furniture and decking).

Ellis