Sloped roof, asphalt shingles (2 damned layers), over 3/4" wood plank. A tiny leak around the chimney caused water to rot out a section of the wood at the roof's edge, and nearby fascia board. I've replaced shingles before, but never done this type of repair. What type of underlayment should I use, and is it possible to get small rolls or pieces, since the job is so small? Any preference on what to use (or NOT to use) to replace the rotted wood? Any and all advice appreciated, thanks!

 

To replace the rotted wood your going to have to strip back the shingles far enough to get to the area to be replaced. It's not just the actual rotted wood you have to remove enough to get to a joist/truss.

Now comes the hard part, replacing the shingles.

Where is the damage, the bottom/eves, or the top/ridge?

Doing it right would probably call for the shingles to be replaced on the entire deck. Not sure how well a two layer repair is going to turn out.

 

Thanks, Marq1. The rotted section (around 24" worth, I'm guessing) is at the eave area (roof's edge), and the fascia board directly adjacent to it, as I stated. The roof is nearing its end of life, so it's going to have to be re-roofed completely in the near future. For now, I'm just concerned about repairing the damaged wood. I'm hoping I can just replace the two layers the way they started. Hope someone can offer some guidance, thanks.

 

Replacing wood damaged by a leak before fixing the cause of the leak is backwards. Once you know the leak is stopped, replace roof and any damaged sheathing. Right now you are guessing where the sheathing is damaged.

 

Beelzebob - I discovered the leak accidentally, while tearing out a bathroom wall to insulate. I could see a tiny pinhole in the rotted wood, where I'm guessing a nail once was shot through the aluminum flashing into the roof. That's where the drip is. Hoping that replacing that section of wood will solve the problem.

 

Wall cavities are usually not open to the roof so I am not sure what you are looking at. You can caulk a nail hole in the shingle from the roof. If this fixes the leak, I wouldn't fix the damaged wood until I reroofed unless there are other issues. You could end up with more leaks than you started with. The hole in the wood is not the source of the leak.

 

This house is full of surprises and oddities. All of the interior walls were open to the attic, and had no insulation (or 2 x 4 studs, even - just furring strips). I'm attaching the view from the bathroom. On the right top, above the foam, you can see the attic insulation. To the left some blown-in insulation I added. In the gap about 6 inches to the right of the chimney is where I spotted the pinhole leak. (Now you can understand better why I ripped the wallboard and tile down, huh?)

You make a good point about possibly making things worse, and waiting for the re-roof. I searched all over, looking for a nail hole in a shingle that could be the culprit, but haven't found it yet. It's probably under the darned wet patch I used at the base of the chimney flashing. 'Doh!