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downers 01-28-2008 10:59 AM

low-slope roof and leaky ridge vent
We bought a home last summer built in 1957 with a low-slope (approx. 2:12) roof. The roof was replaced about 3 years ago by the previous owners with a modified bitumen surface, and the surface itself is in excellent shape. It is a very simple roof -- single gable, no valleys -- and there doesn't appear to be any ice dams or other external problem areas (and we've had a very wet, cold winter here in Illinois). We have a continuous metal ridge vent on the peak of the roof -- and here's where the trouble starts.

Most of our house has a vaulted ceiling. But about halfway toward the back of the house, we have a drop ceiling running directly under the peak of the roof that covers our hallway and bedroom closest. This "attic" area is probably about 60-80 square feet, total, and it must be about 2-3 feet tall at the tallest point. There is no inside access to this space (it's not a real attic, in that sense). During moderate to heavy rains, we are hearing dripping sounds on the ceiling in these areas. There is some water staining apparent on these ceilings, directly under the ridge, but not enough to constitute a major leakage -- it's just VERY annoying (drip... drip drip... drip). We don't seem to be having the same problem with melting snow, which is strange, but I'm not complaining...

We've had two people come out to look at the roof. One (the guy who installed the ridge vent) said that we should elevate the existing ridge vent off the surface of the roof with 2x4s. The other guy said that a metal ridge vent like that is just trouble to begin with (very flimsy and tends to get water reversing back inside), and we should get a shingle-over vent, like the gaf cobra. I am starting to think that a ridge vent on our 2:12 roof is not a good idea at all, and that we should just cover the whole thing and ventilate the crap out of it with soffit vents and a small attic fan.

Any suggestions or comments on the solutions above? The roofers around here don't really know what to do with low-slope roofs (because, let's face it, the midwest is not a great place for them), but we need some kind of solution as we move into the spring!

redline 01-28-2008 12:26 PM

Can you post a photo?

downers 01-28-2008 03:20 PM

a couple of photos
2 Attachment(s)
here are a couple of photos. no recent pics, as there is about a foot of snow up there!

the first is a picture of our house from the back. you can see how low-sloped the roof is... those two gable vents right under the ridge beam are ONLY in the back, as this is the "attic" area that is NOT a cathedral ceiling (the rest of the house is). you can also (kind of) see that we have very wide eaves, projecting out about 2 feet on all sides. these have soffit vents pretty much all the way along them.

the other picture is a stock photo of the type of ridge vent that I am talking about. these are VERY similar (if not identical) to the one we have up there now.

what other photos would be useful? interior of ceiling/moisture problem?

tinner666 01-28-2008 09:37 PM

Too much detail for mr to explain here. I'd turn 2x4's on edge, on each side of the ridge. Run mod-bit up and over them, and re-form a ridge vent there. Used to be done like that many years ago. A roofer like me would call them expansion joints way back when.

the roofing god 01-29-2008 12:01 AM

those always leak at the seams,and ends,also a lot of roofers don`t set them in a bead of sealant like they should

downers 01-29-2008 02:19 PM

I feel like sealing the seams should be something we could probably handle doing ourselves, to see if it would help. Would an all-purpose sealant work?

I got a suggestion from someone else that we should get rid of the ridge vent altogether -- is that possible without a complete re-roof?

the roofing god 01-29-2008 06:07 PM

use elastomer,henry makes one--or remove it,put wood in the space,and cap the area with roll roofing set in flashing cement

tcypranowski 02-20-2008 06:48 PM

Hello, I am new here. I am buying a house with a roof similar to to this in NW Indiana. It has soffit vents but no ridge vent with all cathedral ceilings. I have been told that cathedral ceilings need a ridge vent. is this true? should i install one or wait and see if a problem arises after we move in? is there any other way to vent this roof? are the soffit vents enough??

tinner666 02-20-2008 08:09 PM

It should, at first blush, had ridge vent. Heat rises and soffit vents are the intake vents. Rifge is the exit vent.

PKHI 02-20-2008 08:21 PM

I see those all the time, the water rolls right under the flange of the metal vent, in many cases the hole was cut too big also. I have seen those types of vent cause water damage all the way down to the eave. Not to mention they're face nailed, thats just asking for trouble.

the roofing god 02-21-2008 01:48 AM

YEAH,YOU SHOULD BY CODE(IF NOTHING ELSE)HAVE RIDGE VENT WITH CATHEDRAL CEILINGS,use a rollvent,or airvent style vent ,which gets cap shingles installed over the top,make sure the hole cut is only 1 1/2"down from center on each side,or 3"total so you have no problems

tcypranowski 02-21-2008 08:59 AM

I had an inspection with a thermal infrared camera and the inspector told me that he sees enough air flow with out the ridge vent. He did tell us to watch for signs of condensation but, he said it looks like it should be ok. Can this be true or do I absolutly need a ridge vent right away? Should I wait and see if there is a problem?

Ed the Roofer 02-21-2008 09:38 AM

I am going to go against my normal opinion in your case. If it ain't broke, don't fix it.

After all, there is considerable debate regarding the additional functionality of ridge venting on a cathedral/vaulted ceiling.

From my personal experiences though, I have seen tremendous benefits from properly installing a continuous fresh air intake ventilation system, along with a continuous ridge exhaust ventilation system.

If you too have a modified bitumen flat roof membrane installed on your desired home, then Tinners suggestion about building up a curb would be the most appropriate.

The contractor should cut out the appropriate width slot indicated by the ridge vent manufacturer.

Have your contractor nail or screw down 2" x 4"s laid on the wide flat side on both sides of the slot. Before installing them cut a 45* angle on the side which will face the eave edge, which would be the same as installing a cant strip to taper the transition from the flat roof surface to the vertical projection.

Seal off the ends and do not cut the slot out at the gable sides for about 12". Fill in that gap with a shim cut out of a 2" x 4".

Install the same type of roof material as the flat roof currently is composed of.

Prior to installing the ridge vent, set the base of it in mastic, or even better, a polyurethane caulking sealant. Nail the ridge vent in place. I wouls use the Shingle Vent II and cap it off in a Charcoal Black shingle color to closely match the roof material color, unless the roof membrane has been coated with a fibered aluminum roof coating already, in which case, I would use a greyish or silver color as the ridge cap shingles.

Remember, all of the intake and exhaust venting will not function at all, if there is not at least a minimum of 1 1/2" to 2" continuous air space for air flowage, running on top of the ceiling insulation currently in place.

If there is not that air space, do not even waste your money on trying this ventilation upgrade, because it will not work and would cost too much to make the right conditions for it to work.


tcypranowski 02-21-2008 11:28 AM

Thank you. How would I know if there is the 2 inch space between insulation and roof deck? I do not have any access. No lights in the ceiling or anything. Is there a trick or will I have to cut into my ceiling? Thanks again!

Ed the Roofer 02-21-2008 12:39 PM

If you absolutely have no access, like from canned lights or an adjoining attic area, your options are limited.

You would either have to cut through the drywall or from the roof. If the roof, then cut it at the ridge and make sure you have a roofer on call to patch it up if the air space is not there and you can not productively instal the ridge vent.

More correctly, you should hire a roofing contractor in advance and have him detemine the spacing and be right there on site to do any necessary patching, either by proceeding with the ridge vent in the manner described or by closing it off properly, immediately.


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