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Low Pitch Roof Solutions

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Old 02-17-2007, 03:37 PM   #1
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Low Pitch Roof Solutions

Hello, I'm a new 'member' and I like what I've been reading.

I've been asked to look at a 'problem' roof.

The roof that appears to be about a 2/12 or 3/12 pitch. It is currently roofed with a cold install modified 'rubber roof'. The roof apparently had this same type of roofing material installed previous to the current roof. The previous roof was appox 4yrs old but leaked and was replaced 2 yrs ago with the same type of roof per the suggestion of the roofing contractor. (???)

The low-pitch roof meets at the peak with an approx 8/12 pitch roof. A roof-vent is installed with the membrane roof side "blocked" . This apparently was to stop water from blowing, or backing up into the vent and inside the home from the low-pitch side.

There are rafter-vents installed underneath this low-pitched roof, and the 8/12 roof, and insulation installed, but the inside is not 'finished' with drywall or other material. The rafter vents/insulation end at the outside wall, and the roof over the eave is uninsulated and 'vents' to the rafter vents. This *attic* is heated in winter and cooled in summer and is used regularly as a 'storage' area. The eaves are vented but not as much as "I would like".

With the nasty weather as of late the roof is leaking. It is leaking into the eaves and there are ice-cicles hanging out all of the vents in the eave. It appears that the leak(s) are at the drip-edge or close to it since there appears to be no leaks inside the attic itself. There is an ice dam on the last 3' of this roof.

The roof appears to be installed 'correctly' with only a couple 'pops' in a seam here and there that don't appear to be leaking (from inspection inside). I can't see what is underneath the rubber membrane. I can't see the last 3' of the roof due to the ice/snow.

This problem is the SAME problem that the previous roof had, and I'm wondering about using an ice/water guard under modified roofing. Also, I suspect one of the seams may be leaking farther up the roof, and if there is roofing paper underneath, the water may be running over this all the way to the eave .

I'm wondering what roofing material best suits this job. I'm also wondering if the roof is vented enough to keep the roofing material from being 'cooked off' and/or damaging the seams. Under the right conditions, ie-lots of snow with no wind followed by warm/freeze cylces, a huge ice dam could develope and pose a huge problem at the peak, or a weight problem. I'm wondering if a roof de-icing system is needed.
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Old 02-17-2007, 05:13 PM   #2
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Re: Low Pitch Roof Solutions

Good description for a first question Fixer,

With the frozen bottom 3 feet being unobservable, you may not be able to provide a qualified answer, but were you able to view the bottom eave edge detail on the first row of modified bitumen?

I find that most guys install the mod bit flush to the edge or with a slight 1" to 2" overhang. This is regardless if they had used a proper sheet metal gutter apron/gravel stop edging.

The most likely sounding cause may be an ice dam back up eminating from the frozen gutter. (I presume their is one???)

This back up can go directly under the bottom lip of the mod bit. The better way for this high prone leak area to be detailed would be to make sure the the mod bit extends down on the fascia board and gets terminated behind the gutter using a sturdy aluminum termination bar screwed in every 6" to 12".

Even if the gutter has a flange going onto the flat roof, this would prevent a leak from backing up into the interior. Then if there is a flange, you should prime it and let it cure and then strip it in later.

A minor, yet still necessary aspect is the ridge vent being blocked off or not cut out on the low slope side of the ridge plus the lack of 100 % continuous soffit fresh air intake ventilation. In these situations, when we do install a ridge vent, I install a J-channel inside the Shingle Vent II to internaly baffle and deflect potential weather infiltration.

Additionally, you should reseal any mouse house openings along any seams if possible or else strip a new piece of mod bit over the voids.

Your idea about I & W as an underlayment for torch down will not fly, as the membrane wil melt and be useless. Unless, you instal the I & W shield and then nail down a 43 # base sheet and then the modified.

Alternatively, you could install the I & W shield at 100 % coverage and then use low slope shingling application instructions.



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Old 02-18-2007, 04:56 AM   #3
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Re: Low Pitch Roof Solutions

Thank you for the ideas... I managed to leave out some important info. There is no gutter. This roof drips onto another roof that has a gutter. Also, I can see that the 'drip edge' is *on* the facia... the plywood roofing doesn't overhang the facia at all. The water that IS coming off the roof, drips down the drip edge and onto the facia. I don't like this either. I would like the ply to extend at least an inch maybe more 'past' the facia. This way the water will not have as much a chance to 'travel' into any seam/joint between the roof and the facia. Even the slightest pitch would keep this from happening.

The next time I look at it, I'll get a better look at the soffit construction and how the plywood meets the facia. This looks like a strong suspect to me.

Someone else mentioned using shingles over an Ice/Water Guard material. I'm sure I've seen shingles on such a low pitch, but never installed nor know anyone who has. This roof is basically on a 'third' floor (an attic that has had a very long shed dormer added).

Thanks for the help.
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Old 02-18-2007, 06:28 AM   #4
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Re: Low Pitch Roof Solutions

condensation could be possibly building up inside,maybe? I dont think you can use shingles on a 2 pitch but if you can/do just drop the exposure to about 3"
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Old 02-18-2007, 11:09 AM   #5
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Re: Low Pitch Roof Solutions

There may be a heat loss in the exterior wall soffit intersection or in the general vacinity. If this was the case then no matter what one did to waterproof and vent, the result would be the same.

I almost always use an ice and water sheild under low pitch roofs. At least to point of 2 feet inside the building .
A dripedge that extended out an inch then had a bend that again derected the water away would help. Water surface tension would always be a problem though, always wanting to be sucked back closer to the fascia.
Details that I use on all eaves for low pitch roofs are.
1. Ice and water ( grace ) extending onto the fascia a couple to a few
2. Lay the base sheet down and lap onto the fascia.
3. Lay a starter strip Apx. 18 inches. of the same modified product
( usually torchdown) even with the edge of the roof.
4. Install a extended eave flashing of some thicker aluminum or steel
on the perimeter. Fasten very well. Prime the metal. let dry. Install
finished product.
I have never had problems.
One would also be able to install a gutter and not have the gutter hold away from the fascia, unlike other details that have the thick membrane lapping onto the fascia and held in place with termination bar.
If no gutter one could install a locking strip to lock the eave flashing in place . No exposed fasteners and very wind resistant as well.

As a side note I will mention I have used the low pitch roofing detail on many many roofs without the ice and water shield with the same result, no problems

Last edited by red_cedar; 02-19-2007 at 08:43 AM.
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