NA: POA Home Improvement - Roofing question

[brcase]

So for the Aviation portion of the post I spent most of yesterday afternoon watching airplanes in the traffic pattern while I chased down the water leak around my skylight.

Skylight Seal is in pretty poor condition and looks like it has been repaired (poorly) before. My best Guess is the skylight is possibly 30 years old. The roof seems to be in good condition, I am guessing 10 years old or so. I don't want spend the money for a new skylight so am likely just going to remove it. perhaps put an artificial skylight in if I really miss it.

What prompted this was we had a pretty heavy Idaho rain last week (Sunny Seattle day) and it started leaking around the Skylight. So I pulled back the roofing to see how bad the damage was and develop the repair. Mostly looked pretty good. I have one rafter that will need a small repair and a bit of plywood roofing that will need to be replaced.
The part that surprised me when I pulled it up is that is was pretty obvious that water was getting through synthetic underlayment everyplace there was a nail penetrating through it.

My thought is the shingles shouldn't be letting any water get to the underlayment and 2nd the underlayment should seal around the nail to prevent it from getting through (probably overly optimistic)

Anybody have any thoughts on why I am getting moisture past the shingles and underlayment?
Seems like the only long term fix is to redo the roof, but not sure how I would do it differently? Different underlayment? Different shingle (Currently Certainteed brand)

 

[Bob Noel]

I'll be the bad guy and recommend a professional roofer. If it isn't immediately obvious why there is water, get someone to look it, someone who knows what he's doing.

 

[tspear]

From my limited knowledge, the water marks mean your roof was not installed correctly. The nails should always be covered by another shingle above it (this is why there is overlap).
My guess, and only a guess looking at the pictures, whoever installed the roof before did not correctly overlap the shingles based on both the water marks from the nails, and the pictures of the shingles in the photo.

Tim

 

[brcase]

Thanks for the replys, The overlap looks fine to me. It occurs to me (after the OP) that the issue could be that I was getting a lot more leaking around the skylight than I thought and the water was spreading between the singles and underlayment more than I expected. That would explain the water coming through the underlayment at the nails I am seeing, I might just need to pull shingles and underlayment back a lot further to prove this theory. Not seeing any other cause of the water getting there I am more likely to just double up the underlayment where I had to cut it to see under the underlayment and replace that shingles I removed with new shingles. Hopefully they will match somewhat close and I don't end up redoing the whole roof. Other than the cost of the shingles, even this wouldn't be that bad it is an easy roof to redo. I had just done redone the roof on my previous house (for the 2nd time, it lasted 25+ years) 4 years ago.

Brian

 

[Chip Sylverne]

Can't really tell much without seeing how the skylight was flashed. Properly flashed skylights, or vents or any other roof penetrations rarely have problems. But it's either 100% right or it's all wrong. Doesn't take much of a mistake for wind driven rain to get in.