Building up flat roof for shingles

My garage extends past the back of my house 12 feet. The family room was extended 12 feet to match the end of the garage. The previous owner did this in the 80’s. The family room has roll roofing installed with a low pitch. A contractor has suggested that he can build up the roof to match the pitch of the garage roof next to it and install shingles. He stated that he will install soffit vents and a gable vent. After he tears of the roll roofing, should he install a vapor barrier and some insualation. Also, by building up the roof, it would be about 8 inches under my master bedroom window. Would this be an issue with rain or snow? Thanks

Building up the roof allows better water control and is usually a better idea on additions and other build ons. But you’ll pay more labour cost.Is the roof currently leeking? If its still holding up alright, get it done the same way with a newer type of rolled. Rolled roofing is quick to install, meaning less labour cost. Insulation would be a good idea, but it depends how much room you have for it. A cieling fan in your living room might be more beneficial. As far as a barrier goes, the shingle manufacturers I use have mandatory rules: felt paper or some other type of certified barrier/membrane on anything under 9/12(if you want your warranty). Rolled roofing usually doesn’t require an underlay. That would be an extra failsafe for you i guess. All depends what your willing to pay.

Have you noticed over the past winters how much clearance you have from the snow to your window? Putting heat wire or webbing around the area before snow fall would take care of it.

In the past the, here in PA, the snow has gotten close to a foot on the roof. I will install heat wire after the roof is installed. As far as the vapor barrier goes, I was not referring to the underlayment for the shingles, 15lb felt will be installed under the shingles. I was referring to installing a vapor barrier under the insulation.


Flat roofs cost more to install then shingles. Flat roofs need to be watertite. Shingles only shed water.

With 8" under the window you will have no problems.

2" would be fine. Snow will leak at the same height as water. The snow could be 5’ deep. Still will only leak at the height of shingles.

I don’t see why you’d build up the roof if you’re not having a problem with the current design. Unless it’s being done for asthetics.

As far as snow…snow can be a problem…if it is sitting against a wall, etc. I’ve seen walls/windows leak due to snow several feet high and anyone that tells you otherwise is just silly. Your 8" window probably will not be a problem under normal conditions; if it does leak there isn’t much to do but
jump up there and shovel it off.