water shield installation

Hossman

Does the felt overlay onto the water shield or vise versa? And when installing around flashings like at penetrations, is it overlayed onto the flashing or is it under the flashing? TIA

jproffer

Anything that is above anything lays over it. Everything is from the bottom, up.

EDIT: Hmmm...ok that sounds silly..obviously anything that is above anything lays over it. Otherwise it wouldn't be ABOVE it. Anything higher, on the roof, than anything else, lays over whatever's lower than (on the roof) itself.

Hossman

Thanks. So if I understand you correctly, at a penetration on a slope with deck above and below, the sequence from the top would be flashing over felt over water shield? And from the bottom it would be flashing over water shield over felt?

jproffer

Yes, except that the flashing would go over the shingles also, (at the bottom) when you get to that point.

I would worry about getting the shingles and flashing sequenced right more than the felt and flashing. But yes, if you're going to leave it with only felt for any length of time, flash over the felt at the bottom and under it at the top. I would put the Grace under everything and pull it up onto the pipe, with as few cuts as possible, but you'll need some to make it wrap right. That's assuming you're talking about a pipe, if you mean a vent (which really isn't what I would call a penetration because it's just a hole before the vent is put on), but if you mean a vent, I wouldn't even bother with the Grace in those locations.

When you wrap the Grace around and up onto the pipe, make sure not to get too high so it shows past the boot.

BTW Grace is the ice and water shield

Hossman

ok, thanks

jmorgan

Make sure everything sheds water. The IWS will have to be "blended" into the felt system at skylights and other penetrations.
Jim