Q: What is the best way to install joist hangers?
A: Mike Guertin, a custom-home builder in East Greenwich, R.I., and a regular presenter at Deck Expo, responds: Most decks require dozens of joist hangers, so the faster and more accurately I can install them, the more time and money I can save. I’ve found that preinstalling the hangers on the ledger and rim joist allows me to simply drop each joist in place without having to struggle to hold it in position while attempting to nail it off. Another advantage of this approach is that the joists can be seated hard in their hangers; otherwise, if the hangers are installed after the joists are tacked in place, often there is a gap at the bottom, or the hanger ends up cocked to one side or the other.
But one problem with my technique is that the actual size of framing lumber often varies quite a bit. For example, 2x8s that are nominally 7 1/4 inches deep can range from 7 1/16 inches or less to 7 3/8 inches or more. To account for this, I usually run through my stack of joists and measure the joist depths before installing the hangers. If they vary less than 1/4 inch, I go with the average; any that fall outside the 1/4-inch tolerance on the fat side get a haircut with a chisel.
I use jigs when installing the metal hardware. There are several commercially available joist-hanger jigs, but most of them have predrilled holes that presume some standard joist height, and can’t be adjusted to account for variations from nominal lumber dimensions.
Instead, I take a few minutes to screw together T’s from lengths of scrap lumber, which are sized according to the actual dimensions of the framing lumber being used for each particular job (see illustration, below). Shortening the vertical leg of the T by 1/2 inch places the joists 1/2 inch higher than the ledger, which allows the ledger flashing to slope down and away from the house. To hold the hanger snug to the T while I fasten it in place, I use a FastCap joist clip, which is a wire frame that snaps around the hanger (fastcap.com).