Home & Garden

Installing Joist Hangers With Inconsistent Lumber

When framing a deck floor, the top surface of the joists should be aligned at all bearing points. This can be a challenge when the depths vary, and they usually do. Photo by Charles Bickford.

How can I install joist hangers efficiently when the lumber I’m buying varies in depth by as much as ½ in.?

—Andrea Owens, Framingham, Mass.

John Spier, a builder in Block Island, R.I., replies: Yes, a lot of lumber these days has those differences in milling. First, check to see if the pile is a mix of green and kiln-dried, or even just wet and very wet. If it is, it’ll probably equalize if you leave it stacked with stickers between the layers for a few months. Or, if there are only a few outliers, replace them. If they’re all relatively similar in weight and moisture content, and they still vary in width, you need to address it.

First, decide whether having a flat plane at the top or bottom of the framing is more critical. If you’re building a deck, you only need the tops to be flat. In this case, all of the joists on the ledger and rim joist will have to be installed with their bottoms at different heights. I find it easiest to tack the joists onto the ledger first with a couple of toenails, and then install the hangers from the bottom. (Just make sure that nobody walks out on them before you do that!)

If you’re building an attic or porch ceiling, you only need the bottoms lined up. In this case, just pre-install the hangers to the bottom of the ledger or to a straight line, and drop the joists into them. Where the same joists serve as both floor and ceiling, you have a problem. If you rip or plane down the fat ones, and then they shrink, you’ll end up with squeaks and dips in the floor. If you install them, and they don’t shrink, you’ll end up with humps and bumps. The best thing to do is get better lumber; this is why engineered materials have most of the market for floor systems today. If I do have to use questionable lumber, I generally frame for a flat floor, because the ceiling is easier to fur flat later, and it’s more forgiving. But I’ll still reject the worst pieces—using them is a false economy.

Photo by Justin Fink


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