Step flashing a roof to a wall with continuous exterior insulation requires a decision: Do you bring the step flashing back to the structural wall sheathing behind the continuous exterior insulation? Do you flash to the face of the continuous exterior insulation? Or do you install flashing at both layers?
There’s more than one approach that can work and a lot depends on where the water control layer, the water-resistive barrier (WRB) is—behind the continuous exterior insulation or on the face of the continuous exterior insulation. The sequence of the work plays a part too. Is the continuous exterior insulation applied before the roofing is installed or after the roofing is installed? Then there’s the question, “What about re-roofing in the future?”
Here are three approaches I’ve used:
Whichever route you choose to take, the first step is the same: protecting the roof-to-wall intersection with peel-and-stick flashing.
Before anything else is done, a kickout flashing with 5 inch to 6 inch wall and roof legs is installed. This flashing would go over the ice barrier membrane (click here for how to install a kickout flashing). Then an 18 inch-wide strip of self-adhering, self-sealing flashing tape is applied 6 inch on the wall and 12 inch out onto the surface of the roof:
A 2 inch strip of the release sheet is left along the roof leg of the flashing to lap together with the roof underlayment. The underlayment is bonded to the 2 inch strip of flashing and folded over, back towards the wall to form a ‘J’ dam:
This continuous flashing tape will collect any water that may get beyond the siding and step flashing and drain down to the eave edge where the kickout will divert it away from the wall.
It’s considered best practice to use a drainable WRB behind…