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Old 12-27-2012, 01:56 PM   #1
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slope of a roof for shingles


how much of a slope is needed for use of shingles on a roof?

obviously if the roof is flat you wouldnt use shingles.
one section of my roof has a slight angle to it. im guessing 3 degrees.
right now there is, what looks like a rubber floor mat on the roof.
its dry rotted and cracked and with the recent rain storm (last night) its now leaking.
i want to pull it up, put new wood down and lay shingles but i want to know if there is a minimum slope angle for shingles and what that minimum is.

thanks

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Old 12-27-2012, 02:03 PM   #2
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slope of a roof for shingles


Typically anything below 2:12 pitch (2 inch drop in 12 inches) is too low of a slope for shingles based on manufacturers recommendations.
I haven't done a math conversion but 3 degrees sounds like it is way too flat.

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Old 12-27-2012, 02:37 PM   #3
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slope of a roof for shingles


Pictures will help in this case but there a bunch of ways to add slope to a flat roof.

3 degrees would be about the equivalent of a 0.6:12 (less than 1:12) and way, way, too flat for asphalt shingles. They won't drain and they will leak.
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Old 12-28-2012, 12:14 PM   #4
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slope of a roof for shingles


Yeah on that slope you need to use a flat roofing material, Shingles will be a waste of money.
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Old 12-28-2012, 12:34 PM   #5
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slope of a roof for shingles


If there is a low slope (flat) roof system to begin with why put a steep slope (pitched) roof system ? The lower price installation of shingles will come back to haunt you.
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Old 12-30-2012, 01:48 AM   #6
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slope of a roof for shingles


3 degrees is nothing! we have a flat roof and i say its easily 15 degress
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Old 12-30-2012, 09:12 AM   #7
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slope of a roof for shingles


15 degrees is somewhere between a 3 or 4 pitch so since it technically can have shingles installed on it, I don't know if I'd consider it to be a flat roof.
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Old 12-30-2012, 11:58 PM   #8
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slope of a roof for shingles


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15 degrees is somewhere between a 3 or 4 pitch so since it technically can have shingles installed on it, I don't know if I'd consider it to be a flat roof.
oh. i am wrong then. its less than 15degress because its darn flat.
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Old 01-06-2013, 11:02 PM   #9
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slope of a roof for shingles


Over 4 in 12 is a regular shingled roof. Between 2 in 12 and 4 in 12 can be a shingled roof, but it should have some extra work done (doubled tar paper, snow/ice shield near the edges.)

2 in 12 or less is a flat roof for all practical purposes. Trying to shingle has a very high risk of leaks.
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Old 01-07-2013, 10:25 AM   #10
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slope of a roof for shingles


The correct break between steep roofing and low slope roofing is 3 inches of rise per foot of run. The lower limit for basic three tabs is 3/12 with enhanced underlayment, and reduced exposure. The lower limit for Architectural Laminated shingles is 4/12.

Just because a shingle manufacturer allows it does not mean that it will not leak in a driving rain. They ALL defer to the NRCA Roofing and Waterproofing Manual, which is the Bible of roofing IMO.

If you have trees above use a two ply Mod bit set in cold process adhesive. No missiles? Use .060 fully adhered EPDM over a cover board. In both cases use a cover board 1.5 nches thick so you can install a tapered edge at the drips to break down and keep water from ponding on the drip flanges.

In both cases, run the low slope material up under the steep a foot then overlay with Ice Dams. Run up the steep section to above anticipated drift height. You will get snow drifting over the low slope area, and up in the valley. You therefore must prevent leaks from Hydostatic pressure.

Sure, you can do anything you want, just keep Lasagna pans handy.
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Last edited by jagans; 01-07-2013 at 10:42 AM.
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Old 01-07-2013, 12:53 PM   #11
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slope of a roof for shingles


i keep forgetting to get pics of my roof.... ill try to remember to do that this week then i hope you all can suggest the best, easiest, cheapest way to correct this issue.
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Old 01-07-2013, 02:47 PM   #12
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slope of a roof for shingles


I already gave you the best way to fix your roof, don't you believe me?

You aren't one of those people who waits to hear what they want to hear and then does that are you???

1. Tear off the old roof to the deck.
2. Repair the deck where it is shot. If its small just replace it with 3/4 inch plywood. No you cant use 1/2 inch. It needs to hold roof deck screws.
3. Remove the shingles up slope about 8 feet.
4. Install 1 inch iso insulation. Install 1/2 HD cover board over iso. Screw down through all with 3 inch plates and 3 inch roof deck screws. 1 per 3 sq. ft. Install 12 inch tapered edge around perimeter. Set in construction adhesive.
5. Install one sheet (no seams) of .060 Unreinforced Fully Adhered EPDM, turn down fascia and tag off.
6. Install ice dams over EPDM and up steep roof, under felt above about six feet up.
7. Install starter starter strip and shingles.
8. Install drip edge with minimum 3 inch flange and 3 inch drip leg and hem on EPDM roof.
9. Strip in metal with 6 inch pressure sensitive flashing.
10. Coat roof with white acrylic coating after a couple of months or in warm weather after cleaning with simple green and water.

Have a Beer. You earned it.

Or do it some other way recommended by somebody with one 60th the experience I have, and chase them forever to stop the leaks, but hey, they did have the best price right?
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Old 01-08-2013, 04:39 PM   #13
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slope of a roof for shingles


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I already gave you the best way to fix your roof, don't you believe me?

You aren't one of those people who waits to hear what they want to hear and then does that are you???
not at all.

in this case i have no experience in roofing. this will be the first time ive been on my roof since i bought my house 8 years ago.

so i wouldnt know whats right or wrong.
i like to hear ALL opinions.

right now i dont have shingles on my roof section that is the issue. its like i stated in the original post. it looks like a rubber floor mat on the roof.
the metal edge trim looks like its all pulled off also.

since its dark when i get home from work i cant get good pics, so ill post them this weekend.

please give me that opportunity to illustrate my problem in a more understandable fashion. your suggestion may change after i post pics.

while i do appreciate your feedback. like i said i dont know anything about roofing.
i dont know the terminology or what any of that means.
what you posted looks like it could take me forever and thats probably because i dont know.
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Old 01-08-2013, 06:29 PM   #14
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slope of a roof for shingles


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not at all.

in this case i have no experience in roofing. this will be the first time ive been on my roof since i bought my house 8 years ago.

so i wouldnt know whats right or wrong.
i like to hear ALL opinions.

right now i dont have shingles on my roof section that is the issue. its like i stated in the original post. it looks like a rubber floor mat on the roof.
the metal edge trim looks like its all pulled off also.

since its dark when i get home from work i cant get good pics, so ill post them this weekend.

please give me that opportunity to illustrate my problem in a more understandable fashion. your suggestion may change after i post pics.

while i do appreciate your feedback. like i said i dont know anything about roofing.
i dont know the terminology or what any of that means.
what you posted looks like it could take me forever and thats probably because i dont know.
Given the above i think this is probably not a DIY situation for you. I will wait for the pics to confirm it though, but this is not something you will want to learn roofing doing. More often than not these get bandaides and just leak again. Jags is just trying to save you the hassle of doing this more than once.
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Old 01-08-2013, 07:22 PM   #15
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slope of a roof for shingles


I will add one more post for you, and then not post again. Most steep roofers do not know how to handle low slope roofs.

Steep roofs are water shedding, Low slope roofs need to be water PROOF.

You will be best off with a low slope commercial roofing contractor on this project.

Modified Bitumen can be used, but I like to mop one and torch one, and torches, and wood frame construction do not mix. (Fire) Cold process is an option, but this is a very small roof for that.

Your best bet is probably 60 Mil UnReinforced EPDM, installed as I previously stated.

I have no axe to grind here, and as Andy said, Im trying to keep you from doing it more than once.

Good luck with whatever you choose to do.

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