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Need to replace leaking roof around vent pipe... first step?

Need to replace leaking roof around vent pipe... first step?

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  #1  
Old 03-27-19, 05:49 PM
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Need to replace leaking roof around vent pipe... first step?

Shingle roof, been putting tar around the vent pipe for 10+ years to stop leaks... last time I crawled in attic to check, the plywood had partially collapsed under the leak. Can see the underside of shingles in spots.

I've done some minor roof repairs over the years... basically just going to have to cut out the old plywood, replace with new, and new shingles.

My question is if there is a good way to go about cutting out the bad section? Can I just get in the attic and take a sawzall and cut from the bottom up... through the plywood and shingles? Or would it be better to start up top, remove shingles first, and then cut?

Thanks for any advice.
 
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  #2  
Old 03-27-19, 05:57 PM
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You can, but you will eventually need to cut it again from the top side anyway. I would probably remove shingles first and find the edges of the sheet, pull nails, and remove it from on top.
 
  #3  
Old 03-27-19, 06:43 PM
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Thanks. Makes sense. Yeah, pulling up full sheets, or full cut pieces, would probably be better.
 
  #4  
Old 03-30-19, 08:39 PM
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Ok, removed some shingles and this is the situation. I believe the dark portion around the pipe (circled in red) is all I will have to cut out in the picture... the rest felt solid and took a nail good. Below the pipe will probably be more bad wood, though... how much, I dont know.

To cut the bad wood out, I guess I'm going to have to expose the valley metal all the way to the top (which is only a couple feet more).

Assuming I get lucky and the bad wood only goes down a half foot or so, am I going to have to expose the metal valley all the way to the bottom and replace it all, or can I cut it in half and replace?

Talk to me like I'm dumb if needed... I have little roofing experience.

If you cant see the pics let me know... should be two.



 
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Old 03-30-19, 08:45 PM
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You "can" cut the valley tin below your rot, you will need to remove the entire valley and shingles in the valley on both sides ABOVE your repair. Then lap the valley tin a minimum of 19" if your slope is 4:12 or less. As small as that area is, I would recommend you remove and reshingle it ALL.
 
  #6  
Old 03-30-19, 09:14 PM
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Ok xsleeper, thanks. I'll update.
 
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Old 03-31-19, 02:33 PM
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This is where I'm at with it.

Planning to cut out the red triangle, the yellow lines are where the rafters converge.

Open to any input, if anyone sees problems with my plan.

4 pics, let me know if you cant see them:







 
  #8  
Old 03-31-19, 02:43 PM
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Not very many rafters in that area. You might want to add a little blocking where your top red line is so that you can add an additional piece of rafter left of the vent pipe.
 
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Old 03-31-19, 02:47 PM
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Thanks xsleeper, I'll do that.
 
  #10  
Old 03-31-19, 07:49 PM
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I'm about 3" away from a rafter. There's nothing wrong with sistering 2 2x4's to the rafter, to make the 3" gap is there? I figure that's about the easiest way to do it.

It's only about a 3 or 4 ft. run.



 
  #11  
Old 03-31-19, 08:52 PM
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Well, you would actually need to sister on 3 of them in order to catch it. Probably easier to add 2 pieces of blocking perpendicular to the rafters with one new piece of rafter between them that is 3/4" under the plywood. Or just cut the plywood out to the center of the next rafter.
 
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Old 03-31-19, 09:31 PM
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I should have clarified that 3" puts it about halfway under the plywood, so I think they will reach. I'll probably do that, but I'll do what you suggested if two wont work. Thanks.
 
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Old 03-31-19, 10:03 PM
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According to the measurements on your square it puts it 1/4" under the plywood... or not much to nail to.
 
  #14  
Old 04-11-19, 11:45 AM
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You were right about it not reaching... I thought I had it measured right, but I didn't. I just went over to the next rafter.

Got the hole patched. I suppose my plan now is to put some 30w felt down... extend new valley metal 19" on the top of the existing metal, and then shingle.






As far as shingling the valley... I'm just going to try and replicate how they were originally installed. They had the method where it's cut diagonally all the way down (called closed valley or california cut I think?). I think I've read not to nail within 6 inches of the center of the valley.



Let me know if anything doesn't sound ok.
 
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Old 04-11-19, 12:07 PM
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Sounds ok. Try not to nail in the valley tin at all. That's more than 6" usually. California cut is tricky with 3 tabs... they tend to leak which is why its critical not to nail into the fin. Be sure you are laying full shingles through the valley as they have done in your bottom photo. You don't want any butt joints landing in the valley. This may mean you need to add a single tab or a double tab in as you get close to the valley so that the full shingle spans the valley.

And too late now but the piece of plywood you put in on the right is turned the wrong direction. Plywood always needs to be laid horizontally since that is the strength axis. If you step on the seam between joists, plywood is weak when laid the direction you have that right piece laid. The piece needed to be turned 90 degrees to have the grain running the right direction.
 
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Old 04-11-19, 12:30 PM
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Thanks xsleeper, great info!

Yeah I had thought about doing other methods for the valley, but since I'm tying into the old layout, I figured I was stuck with the way they did it. If it's possible to do a better method when tying in like this, let me know... if not I'll just carry on.

I didn't know that about the plywood, but I 'did' notice when I installed it that it flexed a ton when I stood on it... I couldn't understand why the one above it barely flexed, but the piece I installed did so much. I put blocking underneath it to give it support, but now I know what to do in the future. Thanks!
 
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Old 04-11-19, 12:38 PM
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The blocking was a good move.
 
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  #18  
Old 05-28-19, 06:53 PM
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Finally had some time to resume this project.

Put 30 wt felt paper down, and overlapped it with the existing.

Got a 10" strip of metal for the valley (existing was 14", store only had 10"). Overlapped it about two feet. Didn't nail it to the existing metal, just put roofing cement on the bottom... i figure that will hold it in place good enough, with the weight of the shingles on top.

Starting the new shingles on the bottom going all the way across the valley with full pieces, not nailing in the valley. Then coming over the top from the other side, and will cut those back down the valley.

Tomorrow I will go get one of those roof pipe flashings to put over the pipe, and continue shingling.
 
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Old 05-31-19, 04:40 PM
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Putting the pipe in. I've looked at probably a dozen videos/articles about the best way to install them... I dont think I came across the same way twice, and there were always people in the comments saying it was wrong... haha.

I ended up using this guys method... seems to know what he's doing, i guess. He uses flashing tape to seal the pipe first, and then seal the flashing on top. No nails in the flashing... uses a double fold of tape on the bottom to make a barrier to prevent rain being blown up under it.

Article and short video.

Dont know if it's best way, but it's easy to go back and add nails if needed. I'll be checking it yearly, and I'm going to run sprinkler on roof for a half hour or so when I finish.

I used a slightly different tape than he did, though. I used the stuff from Lowes, that many people use on their windows and decks.



Here it is uncovered, and then with the top shingle laid over it. Not 100% sure about if it's supposed to extend past the shingle or not, but I'm assuming it's ok like this.





Also, the flange is for a 3" pipe, but my CI pipe is 3 1/2". It stretched over pretty easy, and made a really tight fit, so I'm assuming that's ok.

Open to criticism, if needed.
 
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Old 05-31-19, 05:17 PM
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Some guys like to do it the way you have it in the last picture because it might "look best" to cover as much of the flashing as possible. I don't ever do it that way, because of the possibility of wind blown or ice dammed water (I live where ice damming and snow covered roofs are common) running sideways off the semi circle part of the cut... if that water runs sideways 6" or so it could conceivably get on top of the course below. And water does run sideways if it has the chance. If you tear off enough old roofs and examine the damage as you go, you can see paths where water sometimes travels and this is a prime spot... valleys are another bad one... especially if someone used tar and made a dam that stops water from running through.

But if your flashing was on TOP of that row of shingles in your last photo, (it would just have a hole cut in it, slipped over the pipe, the the boot goes on top of it) and the NEXT row of shingles was cut around the roof boot, there is no way water would be able to go sideways from the semicircular cut and get on top of the course below.

That's just the way I have always done them... no Grace membrane, no tar, never had a leak yet.
 
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  #21  
Old 05-31-19, 05:24 PM
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I like that idea. Makes sense. I haven't nailed that top shingle down yet... might change it.

Do you nail the flashing? On the top and maybe the sides, above the tar strip?
 
  #22  
Old 05-31-19, 05:32 PM
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I put one nail top center as i set the boot and after I'm finished shingling the roof I will go back and put a couple exposed 7d hdg nails (or roof nails) on the bottom corners... about 1 1/2" in from those radius corners. Then put a dot of clear sealant on them (like Geocel 2300). I do this all last as there are always a few places you have to face nail and caulk... like on roof vents or on end of the ridge.

I kind of like smaller head nails for exposed nails.
 
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  #23  
Old 05-31-19, 06:44 PM
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Ok, have to tap the metal back smooth, but this is how I will run it.

On top of the one with the hole, one nail on top of flashing to hold it in place, next row trimmed around the boot, then later 2 on the bottom with sealant.



 
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Old 06-03-19, 04:41 PM
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Well, got it all back together. Happy to report that I ran a sprinkler on the roof for almost 30 minutes, and saw no leaks when I went in the crawlspace to check on it. Will monitor it once or twice a year.





Things got a little iffy when I got to where the gable (?) meets the main roof. I took a bunch of pictures when I removed the shingles, and I think I have it back like it was.

The shingle on the left that has the cut out, is an original part of the roof that wasn't disturbed. I just did the same thing to the new shingles on the right.



Only little issue is the top shingle sticks up a little right there. I reused an old shingle that was stiff... maybe I should have used a new softer one?



Guess I can try to put some sealant on it, to try and hold it down, unless I need to remove it and put a new one there. I used all the new ones, though, so would have to track a single shingle down somewhere, unless I want to buy another bundle. Only had to use 1 bundle for this project.

It's my mom's house, so I tried to keep the costs down, and did a pretty good job. After my dad died, things are a little tight for her. My dad and I probably spent 15-20 years putting tar on that stupid thing, lol. The wood finally collapsed partially in the crawlspace under it (shingles stayed intact, though... was really kinda wierd)... so I decided to bite the bullet and try to repair. Wish my dad could have seen me fix it, but if he was alive I probalby would have told him to call someone, LOL.

Xsleeper, cant thank you enough for your help on this.


Again, feel free to critique anything. Thanks again.
 
  #25  
Old 06-03-19, 04:48 PM
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Glad you got it fixed... that's what we are here for.
 
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