I live in Georgia and have a low pitch shingled roof that is leaking.
I brought out two contractor and the first only recommended Bitumen while the second said I could put on either Bitumen or Shingles with a
4" exposed face. I asked the first contractor why they did not recommend Shingles and they said that with a 2.5" slope (e.g. 2.5"/12") Shingles would leak - as I am currently seeing.
I would prefer Shingles since they have double the warantee as Bitumen, but if it is not going to work, then I will go with the Bitumen. What would you recommend?
think if you look at shingles warrantee you might see mention of that warrantee only covering installed properly with a minimum pitch of 'so much' that 'so much' may be more than your 2.5"
However, shingles here in sunny central Florida on lesser pitch roofs seem to last 15/17 yr.. If you don't let leaves or something pile up and make a dam causing water to flow back under em they're fine here. Burn Down white roofing on neighbors slightly sloped roof is 10+ years old and still looks brand new. Amazingly I have a remote garage with 5yr old burn down on it and falling trees and giant flying branches from two recent storms caused not of drip of penetration.. That tree bent the heck out of the whirly round vent thing though.
If appearance isn't a factor and you want long life, use a modified bitumen roll roofing system.
I recommend using a 3-layer hot mopped or cold applied SBS system. Start with an inorganic base sheet (such as GAF's Ultima) a rubberized interply layer such as GAF's Ruberiod 20, and an upgraded cap sheet such as GAF's MOP Granule Plus. With a slight slope to the roof (and thus, no statnding water) this system should last 20 years in your Georgia climate.
They should be fine above 2.0 slope with two layers of underlayment.
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If your roofer says that isn't necessary, ask him to show you the shingle manufacturer's installation instructions. I'd recommend an inorganic base sheet such as GAF's ShingleMate instead of 30 lb felt.
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You do know that shingles don't provide waterproofing, right? Their primary role is to keep the sun's UV from degrading the underlayment. Your roof leaks are no doubt due to underlayment problems - usually poor installation technique is the root cause.
"Looks" are not the point! The shingles I have used on my roofs usually have a 4" per foot minimum pitch, or absolutely nothing is collectible on the warrantee claim, if it leaks. On the part of my roof that is only 2" per foot, after ripping the leaking (new) shingles and underlay off (roofer agreed to do it free, as he simply followed former owner's request that shingles be used0.), I used a fiberglass underlay, then 3-ply hot tar roofing felt, followed by a mineral grained hot tarred cap sheet. Five plys, of which four are likely waterproof. For aethsthetics, you may be able to select a capsheet with an earthtone or other mineral grain surface. Good luck.....
On 30 Nov 2004 12:58:22 -0800, "joshfeingold" scribbled this interesting note:
Yes.
The low slope will not encourage the water to fall fast enough across the surface of the roof. The fact is shingles are only waterproof if there is adequate slope since they merely overlap each other and do not make a water tight seal upon each other. Think of it this way...
Take a couple pieces of aluminum foil. Place them such that they overlap, perhaps on an inclined cutting board. Put a paper towel under them. The towel acts as your house or the thing you don't want to get wet. Pour water over the foil. Allow it to all drain and check to see if the towel is dry. It should be. Now lay the board flat, again with the pieces of foil overlapping and with a paper towel under them. Do the experiment again. Your towel, or house, will now get wet when you pour the water onto the pieces of foil.
Yes, you can try to accommodate a low slope roof with tricks such as squeezing the exposure down, installing the fasteners high, sealing every fastener and joint in the shingles, but the fact remains, shingles are not designed for low slope applications and will not last, no matter how much you attempt to make them do so.
The answer? Use a material or system that is designed for low slope applications. They perform their job well, and the plane of the roof should be flat enough that it is not visible from the street anyway. We use mop bitumen materials and they do great jobs, even on entire houses that were originally hot tar built up roofs with gravel on top as ballast. After tear off and clean up of those kinds of roofs modern roofing systems designed for that kind of application do great jobs and in point of fact, we've never had a call back after installation of this kind of roofing material...at least not from the work we've done!:~)
-- John Willis (Remove the Primes before e-mailing me)
On 30 Nov 2004 14:02:31 -0800, "joshfeingold" scribbled this interesting note:
From my experience, their low slope recommendations won't keep the roof from leaking at the lower end of the range, that is the closer you get to the 2/12 range limit the more likely you are to get leaks no matter what the manufacturer says.
-- John Willis (Remove the Primes before e-mailing me)
If it is feasible, use tin. It will outlast all shingles and other tar impregnated materials. I dont mean flat tin, I mean ribbed steel sheets, also referred to as pole barn steel. That's ALL I use these days on low pitched roofs, and it works great and is easy to install. The only drawback is that it can be a little noisy when it rains, but that dont bother me, and I always apply a layer of asphalt felt under it, which (might) quiet it a little. If the ceiling under it is insulated, the noise is really not noticable, But in a shed with no inner wall coverings, you can really hear the rain. (of course that just saves wear and tear on the weather radio, since you KNOW it's raining).
I have a low roof 2/12 pitch. Original roof was tar and pebbles. Code here says the roof has to be a 2/12 pitch in order to have shingles.
In 1981 I had a shingle roof was put on this house, never got a leak until 2002. Shingles were starting to lift and I had a small leak in the house. The roofing contractor couldn't find any damaged wood, said it was from the turbines. Which have now been replaced by a new ridge vent. This contractor also put a self adhesive membrane on the roof from the drip edge up 8ft.. No plywood sheathing on this roof. All one inch tongue and groove pine.
Have been told the average roof here in central west florida only lasts
15 years because of the heat. Twenty-one years I think is good.
This sounds like my roof. 2/12, asphault shingles. The owner before me put them down. He also laid ice and water shield over the entire roof deck, not just for the first 8 ft.
I have problems with leaks caused by ice dams in the winter so I use a snow rake to make sure the eaves of the house are clean after every snow storm.
When I reroof, I'm not going to put shingles back down. The potential for problems is too high.
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