When installing a roof cap on a roof where there are three layers of shingles, do i trim away just the first layer of shingles or should i trim away all three layers to slide the cap underneath.
Should a vent cap be installed under all the layers of shingles, or just the top most layer
roof
Related Solutions
Any attached worn, frayed or fatigued wiring such as cable TV, phone or electrical supply. As always around electricity, be careful.
Replace it now. Like TODAY. That's BAD.
With that kind of bad shingle wear, your shingles are likely to create ice dams which will cause water to back up and leak through the roof, causing interior damage, compounding the cost.
In the summer, the roof won't hold the water because it can't freeze, so the curls will only grab a very little water before it drips free.
In the winter, however, a little retained water will freeze, expand, and capture more water, which will freeze, and so forth.
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Best Answer
First off, three layers of shingles indicates that you need to redo the roof completely soon. You're at your max, and frankly I think even two layers is a sign of lazy roofers.
That said, vent caps are most effective when installed so that the water runs onto them from the upper shingles and then back ONTO the lower shingles, as such:
So, you should definitely put the cap under ALL layers of shingles above, and over ALL layers of shingles below.