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Clay Roof Underlayment

Mike Lamb

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Looks like clay on top of an old 3 tab asphalt. There is an apparent roofing underlayment under the clay and on top of the old roof. I know the clay roof is only as good as the underlayment. What are your thoughts on this installation?

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Well, the first thing I'd be wondering is whether every row of comp shingles is telegraphing up through the surface and resulting in a roof plane that isn't consistent. The old comp roof, with another layer of felt on top of it, though not ideal is probably the equivalent to the two layers of felt underlayment that's required, no?



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Couple things....

1) baseline, it's crap, but you already knew that.

2) as bad as this sounds, it might actually work OK depending on the flashing (as usual).

3) rusted out metal step flashing that's stuck to the brick w/mastic is a confidence shatterer.

By any industry standard, it's a joke. Because of what Mike said about shingles =ing 2 layers of underlayment, it could work, but I sure as heck would land on it with lead boots in any report my name was attached to.

The moss at the edges just says there's excess moisture right at that spot. I always see moss at the hips and eaves of tile roofs that haven't got metal channel or flashing. Not good, but if it's just at those spots, I'd have a hard time calling it bad.

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I rarely see or inspect anything other than asphalt comp. I believe this is my second clay roof, but after doing some research and driving back today for another look, I think Mike O. got it right and it’s probably OK. I was told that all of this is original 1962 which I didn’t believe at first but do now.

The NRCA says you shouldn’t install clay over anything less than a 4:12. This was about a 3. So this is a cosmetic cover. Regardless, I think they installed a typical 3 tab asphalt and threw an underlayment over that and a clay roof on top of that. There were a lot of broken tiles (my guess is from painters) and the eave may need maint. but I think it’s overall a good system. The flashing needs some maint. but looked good. There was no signs of tar “repairs,â€

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Originally posted by kurt

No saddle behind that last (looks >36" wide) chimney......did you say this one leaked?

Biggest question......how big are the rafters? Lotta weight added to a roof structure.

No cricket and, yes, that is the one that was leaking. I'm leaning towards poor caulking at the counter flashing or very bad mortar joints near the chimney crown, or both.

Rafters were fine and dandy. I do believe this roof is original.

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