Are shingles on shingles a big deal?

[Ron Todd]

Hi BP,

I had an inspection done on a SFR I plan to buy and hold. Most of the inspection went great, but it was pointed out that there are two layers of shingles for the roof and there are two spots that leak. I know it's not ideal to just lay shingles over the existing roof, but is it worth asking the seller to address more than just the leaks?

[Jim K.]

Considering we have @Mark Fries as a resource on this thread, my two cents are not that useful, but from a DIY perspective, what's turned out to be a problem for me in my area is when roofers lay the thin three-tab 25-year GAF shingles over the much thicker original shingles and go cheap on sealing the GAF layer to the original, much thicker shingles. I think that's exactly what @Matt M. is talking about here.

So in these cases you get these big patches of the second-layer shingles that age very quickly, then flap around and crack in windstorms. You've got to get up there with your pry bar, pull the nails, cement and replace all the crap that's flapping and breaking in the breeze. But if you seal down the replacement patch you put in down hard to the shingles underneath with good sealant as you go, your problems, if they're anything like mine, are all over for a very long time.

I wouldn't deal with getting the seller to address the leaks at all. Odds are all the seller will do is get a handyman to get up on that roof and diddle around with his caulking gun loaded with roofing cement among the existing shingles. Two or so years down the line, the patch will start flapping in the wind again and the leak will start right back up.

This is the sort of thing that if you don't have someone who's good and conscientious about small roofing repairs, and they are few and far between in this game, you're much better off handling it yourself, and if you can't handle it yourself, you're doomed to pay for the whole roof replacement anyway.