More Best Practices
Deck ledgers are usually the last of the challenges builders think of when tackling their first exterior insulation project. After all, ledger attachment is so easy—just drive a pouch full of screws, flash the top, and move along. That is unless there’s 2 in. of exterior insulation covering the walls. Then what? How do you fasten a deck ledger to a house with continuous exterior insulation? That’s what I will address here.
Just don’t do it
I have a few solutions to share, the simplest of which is: don’t do it. I don’t mean don’t install the insulation; I mean don’t install a deck. Instead, build a nice stone patio or better yet suggest to your clients they’ll be happy with a backyard meadow. This is the easiest way to avoid additional complexities in a build.
Unfortunately, it’s hard to dissuade clients from their dream deck. So, in keeping with the “don’t” idea—don’t attach the deck to the house. Build a free-standing deck. I’ll come back to the basics of building a free-standing deck, the advantages/disadvantages, and some building code information but first, let’s look at some fastening options.
Off the wall with specialized brackets
If I have to attach a deck to a house with exterior insulation, my preferred method is to stand the ledger off the face of the wall far enough so the exterior insulation—and in many cases the cladding too—can be installed continuously between the back of the ledger and the wall sheathing. There are four proprietary ledger-mounting brackets that will do the job. And there’s a site-made ledger standoff designed specifically for ultra-thick exterior insulation.
The Maine Deck Bracket (MDB) is well known in pockets of the…
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2 Comments
I've had success in getting a local code office to accept a freestanding deck more than 4' high. With good diagonal bracing. One caution: if the deck is tall and the gap between the deck and the house is small, the footings should probably to below the frost line to prevent frost heaving from pushing it into or away from the house.
Good comprehensive advice. I agree with the suggestion to avoid decks if possible - and I'd add if you are including one to use composites or raised pavers as the finished surface, with a low maintenance material for the railings. Over the years FHB has published countless beautiful wood decks, but the description never included the admission that to keep them anything like the photos will require you to give up a precious sunny weekend each summer when you could be doing something much more enjoyable.
One problem with both offset brackets and freestanding decks is they leave you with a section of the exterior cladding behind the ledger which isn't accessible for maintenance or replacement.
Being in the camp that doesn't have problems properly flashing a ledger, I favour using wood blocks for walls with exterior insulation. Once installed it leaves you with the same situation you have in the more typical construction: a continuous wall plane covered by a WRB. The blocks should extend from the bottom of the ledger to a point about 2" above the top to provide backing for the wall flashing.
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