Q. In the article "Building Safer Decks" (6/11), Glenn Mathewson notes that the IRC's prescriptive bolting schedule is limited to uniformly distributed loads and that you may be able to use a tighter fastener schedule to account for a doubled joist that carries a headered opening for steps. Some code inspectors treat the double joist as a girder carrying a point load and don't permit attachment to the ledger board at all, based on IRC section R502.2.2.2, "Alternate Deck Ledger Connections," which says, "Girders supporting deck joists shall not be supported on deck ledgers or band joists." I'm wondering how Glenn applies R502.2.2.2?
A. Former deck-builder Glenn Mathewson, now a building inspector in Westminster, Colo., responds: While the new ledger bolting table in the 2009 code is useful, I'm less impressed with some of the other new deck-related provisions. As for the prohibition you ask about, I've researched its intent and how it came to be in the code, and I haven't found a good reason to outright prohibit a "girder" connection to the ledger. It's a matter of degree, and I try to be flexible. For minimal loads, such as might be carried by a joist doubled to catch a stair header, a tighter bolting pattern at the ledger connection works for me - without an engineer's seal. For larger loads, I like to see the ledger split and the beam hung directly on the band joist. I'm sure some engineers may worry about the rotational effects of loading the band joist from one side only, and while I understand the issue, it would take a really big load to convince me that the band is going to roll out of the house from one beam connection. Each situation is different, of course, and in some cases I may require engineering.
For girders carrying large loads, I prefer to see the beam run into the floor framing, where it can be directly supported on the sill or studwalls. Another option is to support the beam on a post placed near the house, but this requires a solid footing on undisturbed soil - which is tricky next to a backfilled foundation wall.
Ask the inspectors what the intent of the prohibition is, so that you can propose an alternative. Perhaps they will find - as I did - that it's not clear-cut and they'd be willing to accept one of the methods I've described here.
