roof leaks - ideas?

My house has developed a roof leak. Asphalt shingled roof, approx 7 years old and in good shape otherwise. Leak is in the rough vicinity of (actually down about 4 feet and over a bit) from a bathroom fan hood.
I've had a professional roofing contractor over to repair the problem. He came during our first real rain of the spring (when I first got the leak) and patched some areas with "wet seal" while it was very wet and cold out. He assured me that didn't matter.
5 weeks later (last week) we had a TORRENTIAL downpour. I checked the attic about 8 hours later, and my towels and plastic (protecting the ceiling and insulation) were definitely damp. Not sopping wet as anticipated. Also of note is this "wet seal" product (initially black) is now turning a brown/green colour...I'm not so sure thats normal.
Any ideas on where/how to look for this leak? Short of waiting for a good downpour and taking the day off to send my father into the attic and "watch" for the water (which is very difficult in this particular attic), what else can I do? Is the repair going to be hit and miss? I'm not sure i fully trust the garden-hose-soak method, as I can't see it being wide-spread enough to duplicate a good rain-soaking.
Any roofers out there with some experience to share? Please? :)
bmoney
I'm told that the "wet seal" product really doesn't work very well when applied in the cold and wet. Also considering the leak seems to have been slowed up, I think we're on the right track...but how do you know?
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H A wrote:snip-Any ideas on where/how to look for this leak? I'm told that the "wet seal" product really doesn't work very well when applied in the cold and wet. Also considering the leak seems to have been slowed up, I think we're on the right track...but how do you know?
The type of "roofer" who slapped a bucket of tar on your roof afforded me a nice living for awhile! Shingles, 7 years old, I'm going with "bath fan flashing should be redone or replaced". Tom
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Sort of like saying my umbrella is really in good shape except for the missing cover.
One problem with roof leaks is that they often are a distance away from where you see it. I'd take a look at the flashing around the fan for step one as flashing is a common place to start. If that proves to be the problem, you may have some good life left in the roof. Check for any visible cracks that may have opened up. Bubbles and bulges are signs of problems also.
There are some roof coatings that may buy you some time, but in general, that time is a year or two. You'd be wise to start saving for a new hot coating before long.
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It's not a flat deck, Ed. Tom
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Upstream and across 1 joist in each direction there is NOTHING. No vents, no chimney, no penetrations of any kind, right to the peak. However, there is a vent hood RIGHT BESIDE where i've determined the water is coming in. I'm betting money its time for a new vent hood.

This being a sloped and shingled roof, the above doesn't apply :)
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clipped

We helped a friend find the source of water running down a ceiling light fixture. Popped plywood deck, not real obvious. In place of your plastic and towels, lay newspaper over the plastic, wait for the next rain, and check where the newspaper gets wet. Should be more visible. That and paper towels is how I check for toilet leak :o) Then, look above and next to, where water might traverse a rafter before it drips. Any tiny bulges where shingles and/or deck have lifted?
Did you have a lot of wind when leaks occurred? Wind driving rain under vent hood? Ice dams just previous? Clogged gutters?

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I was able to find what I believe is the spot. :( Just to the left of the vent hood, one section of sheathing board (i've got the tongue/groove kind) has split somewhat and a knot in the wood has fallen out. It is right from here that the water drips. The roofer commented its very common to have slight dips and peaks with tongue/groove sheathing as warping is pretty normal. There are no noticeablely huge dips or warps tho.
Its actually interesting - there are intermittent spots on the roof where a shingle has kind of curled or blistered, and then a 10x10 area that is picture perfect. Then another one somewhere else....
Its pretty clear that the flashing around the vent hood is pooched. I'm thinking that when the roofer comes back, I'll just have him install a fresh vent for me, something a little taller. (sick of not using the fan cause its submerged in snow) Though its interesting since the roofer did pay attention to that particular hood, I can't really tell if he hit the left side or not.

No wind, gutters clear and perfectly clean. I had an ice dam in the relative area, but a year previous :) Below the vent hood actually, didn't realize the low-slung vent hood was melting snow that had submerged it...melt ran down and you know the rest. :)
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Leak found! It turns out that my problem was two-fold.
1. The vent hood for the bathroom fan was NOT NAILED DOWN. The roofer was able to lift it almost off the roof with no effort! He replaced it and nailed in the new one properly, and sealed it up good.
2. The PREVIOUS ROOFER, in his attempts to solve the problem, caused more damage. Its a good thing I've got a few shingles left over! In aggressively lifting up shingles looking for problems, he tore one badly - right at the seam, where two others meet. Water was able to just walk right in!
We had a substantial rain last nite and today things are dry - I'm a happy camper! Goes to show you - be VERY careful about who works for you....the "first guy" was from a very large outfit in our town, and it was GARBAGE!
bmoney

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