Ice-Dam Protection: Over or Under Eave Drip Edge?
Code says "over," but best practice may be "under."
An ice-dam leak-protection membrane is essentially underlayment, and the IRC requires that underlaymemt be installed over the eave drip edge. But several manufacturers of film-capped membranes have instructions calling for their product to be installed before the drip edge and sealed over the fascia. The reasoning in this case is that the membrane will prevent ice-dam water from backing up under the drip edge and leaking into the soffit, where it can travel back to the wall of the house. This practice makes head-slapping sense to me — but it goes counter to the building code.
So how do you comply with the code and do the right thing? First, run a narrow strip of self-adhering membrane over the top of the fascia and onto the roof deck. We used a 6-in. roll of ProtectoWrap Universal Primer Free membrane. Then install the drip edge, and install the ice-dam leak-protection membrane over the drip edge.
Sure, it’s an extra step and requires a little more material, but it seems like a good solution and one we employed on the FHB House.
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After going to the ProtectoWrap website, I couln't locate the 6" Universal Primer Free membrane(18" std roll width). I did find a listing called BT20XL Butyl, which does come in 6" width, is white and could be what was referred to in the article. Please clarify....
I don't see the advantage of the 6" membrane over either of the other two methods. It's an extra layer, but a layer that depends solely on the integrity of the adhesive joint on the uphill side to repel water...water that should never be there if the ice and water shield is installed properly.
Response to Jon Seeley - The 6 in. membrane seals the joint between the fascia and roof sheathing. Ordinarilly the joint is only lapped by the fascia leg of the drip edge. In climates prone to ice dams where the dam starts in a gutter, the backed up water can enter the sheathing/fascia joint because the drip edge leg doesn't seal. The membrane makes the seal. There is of course the concern that the adhesive joint could have defects.
Response to PNK - Yeah, the ProtectoWrap website doesn't list all the products they have unfortunately. Find your local dealer who carries ProtectoWrap products and they will be able to get you 6 in. or 12 in. or 36 in. rolls. And you aren't just limited to what ProtectoWrap has, several other companies make narrow flashing rolls of sealing tapes.
Thanks for sharing this useful post. Keep it up!!
Great info
So, is the order of steps this?:
1. install the 6" wide strip of protectowrap over the fascia/sheathing joint.
2. Install drip edge over that.
3. Then install ice and water shield over top the drip edge.