Ugh, found soft spot in my roof today! How hard is this to repair?

**Steve7** · 06-27-2019, 09:32 AM

Jim, that looks fantastic! Nice job!

**Canyonlight** · 06-27-2019, 10:11 AM

Yes, Jim as Steve shared......looks well done !

Dan

**dbphillips** · 12-07-2020, 11:52 AM

I'm really surprised they don't have a gel underlayment on the TPO, to in effect laminate the roof. It would also serve as a second self sealing layer. Optimally, I'd want 240 sq ft of .040" 3M GEL VHB, but that would probably be $1000 on its own. :^D What keeps the TPO bonded to the sheathing, so it doesn't flutter under way? Seems no adhesive is visible.

**Foothills Jim** · 12-07-2020, 12:12 PM

Originally Posted by dbphillips

What keeps the TPO bonded to the sheathing, so it doesn't flutter under way? Seems no adhesive is visible.

I believe he TPO is installed with a water based adhesive that is usually rolled on. The gel underlayment sounds like a good ideal, especially since I've had to repair a second soft spot of the same size found several months ago. It too was caused by a tiny hole about 1/16".

**dbphillips** · 12-07-2020, 12:31 PM

Originally Posted by Foothills Jim

I believe he TPO is installed with a water based adhesive that is usually rolled on. The gel underlayment sounds like a good ideal, especially since I've had to repair a second soft spot of the same size found several months ago. It too was caused by a tiny hole about 1/16".

Interesting. Call me cynical, but I'd want to see white or black adhesive, so we (and the installer, and the warranty adjuster) know it actually got done correctly. I see no indication in the few pics on the website that I've seen of repairs that adhesive was in place, let alone done properly (no bare spots, proper primer/sealant). If it had been bonded properly on that unit with the peeled back roof I saw posted, there's no way that much TPO would have peeled back all at once, unless you ignored it for an extended period of time. That's why you do 100% coverage with a compliant adhesive. Matter of fact, a compliant adhesive would also serve to seal the joints in the sheathing and might take care of the algae lines on the roof.

The RV industry sounded fun when I was a young engineer, but there was no way I could have ever maintained any semblance of sanity...

**iannickb** · 03-01-2021, 10:34 AM

Originally Posted by Foothills Jim

Here's some follow up pictures of the repair.

I cut out the damaged section using a thin cut off wheel in an angle grinder. Not the best thing for cutting wood but I'm more of a mechanic than woodworker and a plunge cut with my circular saw wouldn't have produced as good a result.
Attachment 20977

After cutting out the damage I put some wood scraps between the OSB and the insulation to allow some air to enter and dry any moisture. Then placed a fan blowing at the area.
Attachment 20978

I screwed in three pieces of 1x6" which worked well for my 11" opening.
Attachment 20979

Next I screwed in the OSB replacement piece.
Attachment 20980

I went down to my shop and saw the tube of construction adhesive I bought sitting on my cluttered workbench. Hate it when that happens! I pulled everything back out and then reinstalled using the adhesive and the screws. Thanks for the adhesive tip Andrew and Michael, I wouldn't have thought of that.

I had some scrap laminate from a previous project so I used it to cover the screws on the patched area. I didn't have a piece large enough so I cut what I had in two so I could get all of the screws covered. Don't want any screws backing out and showing themselves later.
Attachment 20981

Nice repair.
Any reason you cut the TPO and you did not unscrew the gutters and the back to lift the whole thing? I was just wondering if it would be a more seamless repair without the tape.

**Foothills Jim** · 03-01-2021, 11:35 AM

Originally Posted by iannickb

Nice repair.
Any reason you cut the TPO and you did not unscrew the gutters and the back to lift the whole thing? I was just wondering if it would be a more seamless repair without the tape.

The TPO is glued to the roof with a water based adhesive. When one pulls it away from the roof it often stretches and doesn't return to it's original shape. I think trying to lift back a big section will cause additional problems. I have repaired two water damaged spots, both about the same size. When repairing the first one I stretched the TPO a bit and the end result wasn't as good as I would have liked. When I repaired the second spot, after making the U-shaped cut I wrapped the TPO around a large dowel and used that to roll it up away from the wood with an even pressure. I also took a razor knife and cut strands of adhesive that were pulling up with the TPO. This resulted in very little distortion of the TPO. The eternabond tape is good stuff. I worry less about it leaking than the original roof membrane.

**iannickb** · 03-01-2021, 11:40 AM

Originally Posted by Foothills Jim

The TPO is glued to the roof with a water based adhesive. When one pulls it away from the roof it often stretches and doesn't return to it's original shape. I think trying to lift back a big section will cause additional problems. I have repaired two water damaged spots, both about the same size. When repairing the first one I stretched the TPO a bit and the end result wasn't as good as I would have liked. When I repaired the second spot, after making the U-shaped cut I wrapped the TPO around a large dowel and used that to roll it up away from the wood with an even pressure. I also took a razor knife and cut strands of adhesive that were pulling up with the TPO. This resulted in very little distortion of the TPO. The eternabond tape is good stuff. I worry less about it leaking than the original roof membrane.

That is interesting. Thank you for all the info. I don't think mine is glued on. I was reading that some are and some are not. That makes me wonder why sometimes they would glue it and sometimes they won't.

**Calbar** · 03-01-2021, 12:03 PM

Originally Posted by iannickb

That is interesting. Thank you for all the info. I don't think mine is glued on. I was reading that some are and some are not. That makes me wonder why sometimes they would glue it and sometimes they won't.

From my knowledge the TPO is always glued on just sometimes not as much or enough glue is used which causes billowing of the TPO and it to pull off.

Rob

**iannickb** · 03-01-2021, 12:19 PM

Originally Posted by Calbar

From my knowledge the TPO is always glued on just sometimes not as much or enough glue is used which causes billowing of the TPO and it to pull off.

Rob

You are right Rob, I just checked mine and only the sides/edges seem loose. I was under the impression that it was just stretched tight.