Tar and gravel roof

[Nicholas Lawrence]

Buying a new house. Think it will serve us pretty well. Instead of shingles, or other roofing material I have dealt with before, it has what I am told is hot tar covered with gravel. I have seen that on commercial buildings, but never on a home. It is not really a flat roof. I measured the slope at about 1.5 feet over 12. Looks to be in pretty good shape, except for a couple of spots where the stones have washed off or whatever, and the tar is exposed.

Anybody have one of these? Good things, bad things, advice or suggestions? Looking mainly here for people who own one, or professionals with experience dealing with them. Thanks for any thoughts.

Nick

[Mike Henderson]

I had bad luck with a tar and gravel roof on a rent house that I owned. That's not a lot of slope so maybe you have to go with something like that. But if shingles will work, there are some 50 year shingles that I'd prefer to tar and gravel.

Mike

[Lee Schierer]

1.5 : 12 is too low of a slope for shingles. Tarred roofs with gravel are used for flat and low sloped roofs. Tarred roofs have a life span the same as other roof materials. If the roof is more than 10 years old you can probably plan on replacing it in 10 years or less. Newer technology is out there for flat type roofs that also have long life spans. I would get a roofing contractor to inspect it along with a professional house inspection before being fully committed to the deal.

[Mike Chance in Iowa]

For awhile, I lived in a house that had the tar & pea gravel roof. There were several neighborhood cats that were determined to find ways to climb up to use the roof as a giant litter box. You'd know a cat was up there when you heard it scratching the gravel and saw all the little piles all over the roof.

[Alan Rutherford]

We bought a house with a roof like that. I don't know the age of the roof when we bought it but clearly not new. It didn't look much older when we sold it about 10 years later. We had some issues with moss (this was in Seattle) which cleared up with some DIY spray - zinc I think. There were no conventional gutters but the lower edges flattened and rose a bit over a width of 6 or more inches to make a shallow trough and holes let the water run out through tarred-in fittings. Wire strainers helped keep them free of leaves and moss but were imperfect and needed attention once in a while. It was a single-story house and access to the roof wasn't bad, which helped. It was easy to walk on.

I wondered what the weight was with all that rock and what it would take to re-roof it. It looked like 2 layers of tarred material - probably re-done once - but I can't imagine cleaning all the rock off sufficiently to put down more roll roofing without stripping the roof.

It might turn out to be a very good roof.

[Mac McQuinn]

Seems like the framing on this house would need to be pretty substantial. The weight of stone and tar plus a decent snow load which Virginia can get will add up, requiring a well thought out roof structure. I would try to check this out via attic access, etc.

Roll Roofing works pretty well for low pitch roofs, I've used it a couple times on add-on patios with no issues. Installation and the correct weight roofing makes a difference in life span.
Good luck,
Mac

[Shawn Pixley]

My house has a "flat" roof with a slope of about 1.5 inches per foot. When we bought it, it had a built up roof (tar and gravel). We replaced it about 15 years ago with a single ply membrane of a commercial grade. Much better. You will pay more initially but but it will last much longer. Make sure the installer is trained and certified by the manufacturer.

It is incredibly slick when it gets wet, so be careful if you try to go up there when it rains or first thing in the morning when the dew is still on it. It is best not to walk on it more than absolutely necessary.

[Brian Henderson]

I owned a house with a tar and gravel roof for 17 years, it never gave me any problems, but the section that had tar and gravel was flat and therefore, nothing ever washed off of it.

[Nicholas Lawrence]

Thanks to all for the comments.

The spots without gravel are maybe six inches across, and there are only two or three. I used a bucket of some super- sticky tar like (but cold material) once to patch a leak around a vent pipe. I am thinking I may slop some of that down and put rocks on the bare spots just to protect the tar from the sun.

I agree 1.5 over 12 is not enough for shingles (from what I read anyway), but when looking around the neighborhood you can see 3-4 houses that are pretty much identical that now sport shingles. One of the reasons I thought I would ask here, where nobody is actively trying to sell me something.

As far as framing goes, it looks pretty solid from underneath. Been there since 1959, and has survived the last ten years, all of which saw pretty large accumulations. The sheathing looks like it was all replaced in 2002.

We factored replacement in the next 2-3 years into the offer.

Not walking on it is good advice for any roof I think, but sometimes you do have to.

[Ken Fitzgerald]

We had a house with tar and gravel roof. We lived in it 20 months and had issues.

By most advice, 1.5" over 12" isn't enough slope for standard shingles. I'd go with a commercial membrane as advised above.

[Joe Mioux]

I have a 50+ year experience with flat roofs. A tarred roof failed frequently. In 1990 we built a new retail shop and used a rubber roof with river rock ballast. 27 years no issues.

Another building I own is a flat roof with a rubber roof no rock. excellent service.

Still another building with standing seamed steel roof. excellent

plus a few others with traditional asphalt shingles.

Rubber roof would be the way I would go