Ridge vent leaking? Or what?

We had a new roof put on 17 months ago. It is a low pitch roof (2-12). A continuous ridge vent was installed that runs the length of the 50’ 6" roof. Not long after the job was finished I called the roofer back to point out to him what looked like a couple of small yellowish drip stains running down (maybe 6" long) from near the exposed center beam in the living room’s 12’ wide cathedral ceiling. Without getting on a ladder, he looked at it and said it probably was condensation. We decided to monitor the situation. After a time, the stains disappeared and we assumed he had been correct.

During the past 17 months though we would occasionally discover spots on our living room furniture and floor. My wife thinks these usually appeared a few days after a rain. We would examine the ceiling, but could see no stains on the ceiling, so were at a loss as to what was causing this. I believe I did stick my head up in the crawl space during one storm and could see no dripping anywhere, but don’t remember if there were subsequent spots on the living room floor.

We even thought that it might be something in the leather furniture “expressing” moisture (or some sort of oil/resin) outward. Since there was no ceiling damage, we did nothing.

About 6 weeks ago, after over 2 years in the house, we discovered what appeared to be evidence of mold on the east side of the beam (the side where the stains were appearing below) and some dark spots on the ceiling. A mold technician advised using Spirocidin to deal with the suspected mold. We did and thought the problem solved, but recently noticed more spots on the floor. Inspecting from a ladder today I was amazed to find numerous droplets along the bottom/east edge of the beam. Running my hand over one area of that side of the beam, I found it to be quite wet. There are also now more black dots on the ceiling extending out about 18" from the center on that side. We had a mild rain 3 days ago, but don’t remember any wind.

I began to wonder if the ridge vent could be the culprit and got up on the roof and took the attached photo.

I don’t know what the ridge vent looked like right after installation, or if there is a problem with this, but I am wondering if the waviness evident is problematic or normal after 17 months exposure to sun and weather. After searching the web a bit tonight, I am beginning to wonder if the ridge vent should be removed and some other form of venting installed. What do you think?

  1. Too low of a pitch for a standard specification of applying ridge vent.

  2. That cheap piece of Coro-plast ridge vent has No External Baffles.

  3. What about the continuous Intake Ventilation? Was that addressed?

  4. It could even be the shingles and capillary action of moisture migration, but I doubt it, but just tossing around another explanation, since a standard shingle application does not meet spec on that low of a slope.


Pitch is way to low for shingles and that last course is set high over the key. Is the whole roof like that?
Is there a paper or peel n stick underneath…or is it a go-over?

Also, if that turbine whirlybird vent in the background is on your roof, the ventilation flowage is being short-circuited.

Additionally, look at the up and down waviness to the ridge vent product itself.

Every nail position from the cap shingles sank the vent down at the point of nailing and lifted it up between the nails creating a gap.

If that had installed a continuous bead of caulking and added more and proper nails, the cheap ridge vent wanna-be product “May” not have leaked.


yes its to low of a slope but i could make aluminum ridge vent or turbine vents work without leakin.

imo any of those ridge vents that you nail cap shingles over with 8 penny nails is are junk.

so whatever1,
get the vent off there and have someone put
aluminum in there place.
you have the rite shingle(3tab) for your low slope.

youll be fine.


[quote=“gweedo”]any of those ridge vents that you nail cap shingles over with 8 penny nails is are junk.
you have the rite shingle(3tab) for your low slope.

Hi Gweedo, Can you give me an example of a good ridge vent? The supply near me has cobra, is that ok? any favorite you’ve found?
Also I was planning to use timberline or landmark but I’ve got one wing of the house that is 3/12 pitch, Do you think I can get by with them on that low sloped area or should I consider 3 tabs ? I’ve put down new plywood and already double covered the deck with titanium in this 3/12 area, so it’s smooth and strong.
Regards, DaveB

Although you did not request my opinion on brands of ridge vent, I must state that the metal ones from Air Vent function well, but have installation problems often.

Every spring, I get dozens of calls to fix someone elses metal ridge vents and they look like crud too.

The brand I exclusively use, is Shingle Vent II, but the Cobra Snow Country is a near exact knock-off duplicate, so I would recommend either of those two brands.


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Dave you did’nt ask my op either but I’ll advise you not to shingle the 3 twelve w/out using a waterproof underlayment

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Thanks guys, always glad to get anyone’s opinion.
Ed, I was looking at those ShingleVentII online and thought they looked pretty nice.
Krakkerjak, I’ve got new titanium UDL30 on the 3/12 area now with the sheets half lapped 27 inches. The old three tabs were fine on this slope, do you think the 30 year timberlines or 30 year Landmarks will have problems due to their texture?
Regards, DaveB

You “Should Be” okay, but there are more problems with architectural shingles on a low slope than a flatter 3-tab.

If it installed correctly, but in a snow area, (I can’t remember where you are from???), you really should consider installing Grace or another brand of Ice and Water Shield on the entire roof deck at a 3/12, but then the proper balanced ventilation becomes even more Critical.


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Going over previous ground and adding some
Returning from trip, we were told that, when the remnants of Hurricane Ike came through (Sept. 13-14) there were 60 MPH winds with a little rain. We did not note anything unusual inside the house.

Saturday, Sept. 20: We believe there was a light rain on/off, with no wind. No rain the next 2 days.

Tuesday, Sept. 23: We had an east window, south French doors, and west entrance door open most of the day. The inside temperature rose to 78°. The inside relative humidity was 71%, and 68 a little later. We started the air conditioner. The house cooled down later in the day. We kept the doors closed.

We noticed spots on living room floor and the west side of the main ceiling beam in the living room was very wet. We could see vertical drip lines on the beam, and drops on the floor. There were also some black (mold?) spots on the ceiling near the east side of the beam, over an area not more than 18 inches from the beam.

Opened a bedroom French door slightly around 10 and closed it around 4 AM.

Wednesday, Sept. 24: It was cool. May have opened a south French door a little for a short time in early morning. In mid-late morning, climbed up to check the beam. It felt dry, but a little cool. Went out and left the house closed. Returned after 2 PM, the sun was out (partially cloudy) and it was warm outside, but only around 74-75° / 68-70% inside. We opened the studio window, carport door, and front deck door. Climbed up ladder: west side of beam was damp with a few drops of water on bottom edge. By then the inside temp was 76°. Closed the doors and put the air conditioner down to 75. A little while later, turned on the house fan so there would be constant circulation even when the air conditioner isn’t running. 7PM: beam is dry.

Replies to some posters; thanks to all:
“what can happen: cloudy day / roof doesn’t heat much / beam stays near interior temperature. Night / turn off any heat / beam cools from the interior, also cools significantly from cool air drawn over it via ridge vent. beam cools to 55 degrees or colder… morning, you cook or turn on an unvented gas heater, open to bathroom - just took a shower. hot moist air rises to ceiling, encounters cold surface of beam. If the dew point of the hot air, say 65 degrees, is higher than the temperature of the beam, moisture will condense on the beam, and the air around it will be supersaturated with moisture. Sometimes more/less - don’t notice it. Sometimes beam warms quickly enough that it evaporates. Other times, it drips. At other times, there is no noticeabl condensation, but your beam is living in a rainforest environment…
If you didn’t notice any significant decrease in cooling costs after the new roof was installed, I’d leave the roof unvented. If I did use vents, I’d use roof turbines at least five feet from the ridge beam.” (harry chickpea)

We don’t know if we have saved money, but my wife belies the AC is coming on less frequently this year.
Are you suggesting turbines in addition to the ridge vent? How many?
We find harry chickpea’s condensation theory compelling, but the suggestion to “unvent” seems radical and doubt we would find many local builders in agreement. Complicating matters is the fact that we are in the process of moving out, having sold this house about 3 weeks ago. We’d like to discover reasonable suggestions for action, but the decision will not be ours.

“Is the leak/stain anywhere near the plumbing vents? Did you happen to look at the flashing around them?”
Not really near plumbing. See photo of pipes.

“The other argument against the condensation idea is it should occur in more than one spot, maybe all along that ridge.”
The moisture does seem to extend over much of the west side of the beam, though not evenly.

“Do you know what kind of underlayment they used?”
The contract (my stipulation) called for:
Install 2 layers [req by Tamko warranty for low roof] water resistant 15# felt to decking.
This was supposedly complied with.

“What about the continuous Intake Ventilation? Was that addressed?”
Not sure exactly what is meant, but the house has wide overhangs all around and vents in soffits. From outside, they appear unblocked.

longer shot of present roof

close-up of plumbing vents


even more images: http://s462.photobucket.com/albums/qq345/hopnort/roof/

yeah the cap just looks to flat.
and that style of cap, which i do not like, needs alot of slope.
and i dont think an aluminum ridge vent looks bad.
i think it looks better than regular cap shingles
with an inch of mesh inbetween them and the ridge.

search aluminum ridgevents online.

yes i do install cobra vent.
no i dont like it as much as metal vents.

daveb, unless you live in arizona, it is not a good idea to put architecual shingles on anything less
than a 4/12/p