Flashing under deck ledger
I think I saw this briefly in a Perkins bros video but haven’t been able to find much information on it.
We have a deck that has a walkout below it. The deck ledger is attached to ice and water membrane on top of taped zip and has metal flashing on top of the ledger board. CZ6. Siding will be vertical cedar siding.
Is it best practice/necessary to also add a metal drip cap flashing below the ledger board that would sit on top of the lower course of siding? Or unnecessary?
Thinking that if the siding is on a rain screen, any water that does get behind there would just drain out. Any thoughts or detail drawings on this appreciated. Thanks all–
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Replies
Sean,
You want one of two conditions at the bottom of the ledger: A drip-flashing, or the bottom of the ledger notched out to accommodate the cladding.
Your cladding should always be detailed to exclude water intrusion, and not rely on the rain-screen gap for that. A rain-screen is a secondary layer of protection for when things go wrong, not a primary one.
If the ledger is mounted on the rain-screen furring, the flashing both above and below the ledger should also be mounted on the furring to maintain the continuity of the cavity from foundation to eaves.
I also like to drop the ledger 1” below the deck joists to provide a drainage path. The drip flashing gets sandwiched between the ledger and the end of the deck joists, as shown in the sketch.
Just out of curiosity, is there a reason you prefer the dropped ledger to flush with deck finish level?
The most vulnerable point on the deck is the flashing above the ledger, so raising the joists provides a path for any water or debris that would otherwise be trapped and accumulate on the flashing to drain or be removed.
I agree - another good option is the ledger being flush with the top of the decking, or a bit higher. The worse is the most common: flush with the joists, with the flashing run along the top of them.
Agreed, I was just curious if you had an install preference to the dropped vs flush with decking or higher, or a maintenance reason to one or the other.
Thanks Malcom. There isn't furring behind the ledger (using a 3D mesh rainscreen on this wall - above an below). In this case, I'll slip some drip flashing up underneath the ledger and over the siding. Appreciate the quick response -- hard to find info on this one for me.
Sean,
To be fair, the flashing or notch below is what I'd call best-practice. The most common detail you see everywhere is a bead of caulking between the ledger and cladding below.