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.
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.
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.
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
(Remove the Primes before e-mailing me)
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.
(Remove the Primes before e-mailing me)
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.
Hopefully this roof will outlast me.
On Tue, 30 Nov 2004 23:07:07 -0500, email@example.com (Pj Mack) wrote:
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
When I reroof, I'm not going to put shingles back down. The potential
for problems is too high.
I had a bitumen surface done to a set of stables I have in the back of
the house. Same roof problem as yours, very slow & gradual slope that
alowed rain water to accumulate and back up under the shingles. Reason
being is that the shingles would, as they aged, take on sort of a
concave shape, creating a channel across the middle of each shingle, so
that they formed a depressed area for the water to accumulate and
eventually leak as water acumulated or backup due to debris. I'm glad I
did it as there are no seams for the water to back up into and leak
thru. Of course, these are horse stables and the roof happens to slope
toward the back of my property, so the white color of the roof surface
was not an issue. Not sure if this process comes in more aesthetic colors.
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
On 30 Nov 2004 09:55:32 -0800, "joshfeingold"
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