Extra Footings In Lieu of a Ledger
Footings need to bear on undisturbed soil, dig down to where foundation footings will bear.
I’m considering adding a deck to my small cottage. After spending time and effort on a meticulously sealed and insulated building envelope and rain-screen system, I can’t fathom hanging my porch on a ledger. After reading about all the required fasteners (“Critical Deck Connections,” FHB #258) and considering the necessary flashing to avoid rot, not to mention the disaster that any movement of the porch could reap on the existing house, why do so many people use ledgers? Another row of footings to make a freestanding deck appears less expensive, less complicated, less risky to the existing structure, and less difficult to build. Am I missing something?
— Adam Dinsmore, Pawling, N.Y.
Justin Fink: Freestanding decks are certainly common. The only thing you’re missing is that footings need to bear on undisturbed soil. A foundation surrounded by fill from the construction process qualifies as disturbed soil, so you’ll need to dig down to where the foundation footings are bearing.
That’s not impossible, but it’s likely going to involve more labor than installing a ledger. You could use helical piles (see “It’s Time to Consider Helical-Pile Footings” in FHB #260) in place of traditional piers. You also may be able to talk to your inspector about digging to the usual frost-depth level but then providing some means of compaction and proof of bearing capacity. It’s worth a discussion, but it’s not something I’d try to cheat my way out of, because a sinking porch will be a hassle to fix.