Roof Repair Question

[DGB]

A 2014 Keystone Fusion Toy Hauler:

Leakage around the forward A/C. First, found a tear from a tree limb at RV park but there is a dip in the roof near the tear. It seems to be between the ribs and I think it's contributing to water running below the A/C. I suspect it had this dip when it came from the factory because I've had intermittent leakage since new.

My question: I have the roofing (TPO) removed in this area and will replace with new, using liquid adhesive to hold the TPO, then eternabond tape and Dicor sealant around the edges. However, I need to fill the dip (about 16" by 30" in circumference) before I put the TPO down. It's probably 1/2 inch deep at the lowest point.

What kind of filler should I use? I see Dyco 20/20 seam seal AND Kool-Seal Acrylic Patching Cement. Would either of these work under the TPO to level the roof dip?

I really don't want to cut out and replace the plywood, (actually, OSB) but that may be the smartest choice.

[MidMOTraveler]

I bet you already know what needs to be done.
Open her up and do it right one time.
Sorry and good luck!

[mohead1]

Replacing the wood is the right way.....sorry....sux i know. However there are leveling products out there used on plywood floors to bring things closer to level say when putting vinyl floors in. Trowled on, then screeded to level spot....check Depot/Lowes etc

[kksfish]

I once had some work done on a built up rubber roof where I was employed and to build a valley for drainage around a rooftop AC the roofer used several long pieces of the roofing material stacked to obtain the desired level.
Could you build it up tp what you need if the TPO is in good condition otherwise?

[Hblick48]

I wonder if light weight auto body filler might work?

[MidMOTraveler]

I don’t think anything but cutting out will work.
Floor filler, auto body filler on wood ? I suspect if there is sagging at the AC unit there is underlying damage.

[DGB]

I appreciate the suggestions and I decided to do what really needed to be done. I cut that sagging spot out and I see that it was just crappy work by Keystone. The didn't get a crosspiece flush so there was no support. At least, everything underneath looks new and clean.

[ChrisM]

DGB, how did you splice the new section of TPO to the existing one? Seems the right way is heat welding but I've also seen documents from Alpha Systems describing the use of their product P1671 Rubber Splice Adhesive on patches and wondered if that, or another adhesive, was an option for a splice going all the way across the roof.