On a pitched roof, my understanding is that the rubber underlayment
should go down first, then the drip edge. I'd have thought that the
drip should go first: then, any water captured by the membrane would run
off over the drip. I can guess that putting the membrane first lets the
it seal the drip nails. But, to what end, if there's no place for the
water to go?
Can anyone shed any light on this?
looks like a couple of schools of thought here:
remove the "not" from my address to email
On one of the HGTV shows, choosing the best home-improvement guy, the
judge dinged one of the contestants for putting the drip edge over the
roofing membrane. The judge wanted the membrane over the drip edge to
guarantee all water was kept out, just like the OP thought was correct.
It's a holdover from the building felt days. The edge on top on the
sloped sections held the end of the building paper down - prevented it
from curling back up - and prevented the wind from ripping it off.
With self-adhesive membrane that is no longer an issue, so the
location, top or bottom, of the edge doesn't matter on the slope. On
the low edge drip edge should always be under the membrane.
When I shingled our roofs, I installed the drip edge along the bottom of
the slope first, then installed my roofing felt over the top. This way if
water finds it's way under the shingles, in theory it should flow down on
top of the felt, then over the drip edge. If the drip edge were on top of
the felt, the water would go under the drip edge to the wood decking. I
don't see why membrane would be any different.
On the sides of the roof slope, I installed the drip edge after installing
the felt. This keeps any rain that may be blown under the edge of the
shingles on top of the felt, and not blown under the felt to the wood.
On top of the drip edge at the bottom.
Under the drip edge on the sides.
The OP asked about 'rubber membrane' which obviates the necessity of
doing it the traditional way that you mention. If you think about it,
if the wind is blowing hard enough to push rain sideways between
adhered membrane and drip edge, I'd be more worried about the whole
roof being lifted off.
Interesting timing. I just returned from the library and the current
issue of Fine Homebuilding answered this very question. There take
was that the membrane should be under the drip edge, and wrapped over
the top of the fascia (hidden by the drip edge). I never did it that
way, but it makes a lot of sense, particularly in ice dam territory.
Hmm... I suppose wrapping over the top of the fascia would prevent the
issue of water going under drip edge to the wood decking. Good to know if
I'm still around in 15-20 years when I need to reroof our house. :)
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