Minimum pitch for shingles

[maradcliff]

I have a small shed roof to re-shingle. It now has roll roofing on it. I would prefer tab shingles, but the guy at HD said he did not think it is not steep enough. I could tell he was not sure of his answer, which to me means he was only taking a guess.

The roof is 12 feet from peak to drip edge, and is 13 inches higher at the peak. That means just a tad over one inch drop per foot.

Is that enough for shingles? I really hate roll roofing, and I already have enough shingles (or almost enough). They are left overs and the roof will be several colors, so if I got to buy one more bundle it will still be the cheapest way to go. Otherwise I may use tin, because roll roofing never seems to last long, and is a pain in the butt to apply since all the joints need messy tar.

Mark

[Roger]

We have 2"/foot pitch on one area of our roof, and all shingle warrantees are void at this pitch, according to the package, so we used a three layer hot tar roll roofing, with fiberglass base layer underneath, and walkable granulated mineral felt as a cap . Our other pitch is 4"/foot, and barely passes the manufacturers rate of pitch for guarantee to be valid, so we used regular self sealing asphalt shingles there.. If you still have the labels or packaging on your shingle stock, you might look there, as they usually have a minimum pitch printed there. Bottom Line, it looks like you may indeed be better off with tin, if you have only one inch per foot drop. Good resource, as usual, is Google. Enter phrase minimum roof pitch for shingles

[Jeff Cochran]

The hrozontal distance is what's important, but you're close enough here.

Most shingles are a minmum of 4/12 or the warranty is voided. Roll roofing in half-lap is recommended, as would be any solution for flat roofs. Most metal I've seen is 3/12 or higher, but a solid run from peak to drip edge should work, especially a crimped standing seam.

Of course, this varies by location as well, because snow loads and ice dams could make this moot...

Jeff

[John Willis]

On Fri, 27 Aug 2004 23:33:07 -0500, [e-mail] scribbled this interesting note:

Try a SBS modified roll roofing product. Lasts far longer and gives much better results.

Here's one example. There are others.

-- John Willis (Remove the Primes before e-mailing me)

[DanG]

By your description, your roof is just strong of 1 in 12.

Asphalt or wood shingles will not work.

You could use: Modified bitumen for a granule roof. It can be applied hot or torched down. Metal building roofs are quite normal at 1/2 in 12. Yours would be an ideal candidate for metal. You could also consider elastomeric over foam (not DIY).

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]

[Travis Jordan]

The slope isn't steep enough for shingles.

Use a properly applied modified bitumen roofing system and you'll have a

30 year roof. When I redid my flat roof last year I used a GAF 3-ply system with a fiberglass (non-organic) base sheet, a rubber interply layer, and a granulated modified bitumen cap sheet.

Cold applied system:

Hot mopped: Torch down:

[I-zheet M'drurz]

You sound like you kn ow the business, so I'll ask you for a quick answer. It's kind of hard to Google for something when you don't even know wht it's called!...

In a previous home, I had a flat roof redone and they used a big, seamless piece of rubber. Cost me a small fortune, but the guy guaranteed it for 15 or 20 years, can't remember.

Was I halucinating, or is there such a method/product for doing a flat roof???

A name or just product class would help get me started on my search. Thanks.

[DanG]

It is an EPDM roof. It is very similar to the material used in tire innertubes. The joints are the problem areas as they are glued together and if there is to be a problem it will probably be joint or penetration related.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]

[Bruce]

All the shingle manufacturers I am aware of require a minimum 2:12 pitch to install their products and get a warranty. However, the warranty isn't that important and you can use 3-tab shingles on a 1:12 without a problem if you install it correctly.

The best installation of 3-tabs in your case would be to first clean off the decking and install one layer of "Ice & Water" shield. This product will seal around the nails and prevent leaks. If you don't want to do this you can install 2 layers of #15 felt and then install the shingles with a reduced exposure and the nails placed a bit higher than normal.

I don't normally recommend straying from the manufacturer's installation specifications but we have done several porch roofs in this manner without a problem. Just make sure that you keep the roof free from leaves and other trash so the water won't back up behind the "dam" and possibly get under the shingles.

Bruce A&B Construction Houston, TX

[Dave Combs]

In Orange County, CA the building code will allow shingles where the drop ratio is 1:12. I know because I was just at the limit when I replaced a tar and gravel roof with shingles. Also, I built a shed with the same pitch for architectural symmetry and no leaks there either.

Good luck!

Dave

[I-zheet M'drurz]

With that HUGE Average Yearly Snowfall you folks have, that's downright amazing!

[bumtracks]

Just had that leak with a 2hr 3-4" rain per hour storm and 1.5" pitch here in floriduh, under the old oak tree is fine but under the old cedar tree was compost.