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ChrisHelvey 01-21-2014 12:04 PM

New motorhome roof
Hello all,
I have a 38' class A motorhome and have torn off the old roof, adhered new 3/8" plywood on top and have a 10' wide sheet of TPO coming in for the sealed top membrane (no seams here.) I'm having a difficult time finding an adhesive product that will bond TPO to plywood, available to a non-commercial-roofer.

Any advice on what product will work for this is highly appreciated. I live in a small town and none of the local roofers here do TPO, so I can't get any "leftovers." I do have a fairly robust Ace hardware and a Lowes within reach. Any thoughts on this? (Please don't tell me I should have used EPDM or PVC. The TPO is on its way.)

I see Amazon has TPO primer I can get.

Thanks to everyone,


ChrisHelvey 01-21-2014 01:23 PM

Ah Ha! I found it!
From "Lucas Universal Bonding Adhesive For EPDM/TPO/PVC (1G)" plus a TPO primer and a TPO lap sealant for around vents.

I will use a sealant tape for the edges where it attaches to the vertical side.

Still, I'll take any helpful hints anyone with experience here has.


1985gt 01-22-2014 11:40 AM

I did our old 60's forest river TT with TPO, mostly because we didn't have any white EPDM in the shop at the time.

What I did was.

1.Removed all vents from the roof.
2. Removed the metal drip rails from the sides. Not sure if yours has the metal or plastic ones.
3. Lay out the TPO get it straight ect.
4. Pull TPO 1/2 way back. glue the new plywood first. the wood will take a bit of extra glue, don't skimp there. Then glue the sheet.
5. Allow the glue to flash off. roll TPO sheet, keep the front edge in a semi circle. TPO rolls out nice and easy.
6. Broom it down using hard pressure.
7. Pull 2nd part of the sheet back and repeat the steps.
8. Get all new vents. sealing the old ones will be hard.
9. Install new vents in "water stop" or "water cut off mastic" a small bead on the flange goes a long way. make sure to cut the holes in the membrane first. Screw them down with flat headed screws.
10. Clean and use the TPO primer and cover tape to strip in the seams of the vents.
11. Install the drip rails on the sides. Cut off the extra membrane. Use new screws.
12. Install Termination bar on the front and rear. turn the T-bar upside down so the leg is sticking down. Very carefully caulk this edge so no water can migrate in. A small bead and soap and water will help you keep it look neat.

Good luck they will last a long time.

Dont just set the vents down in goop like they do with the new campers. I bought 2 new travel trailers, one last year and one two years before hand. Both roofs were White EPDM, but all the vents were just set in goop with goop smeared around them. Wrong way to do it IMO.

We've done a few campers and food trailers with EPDM and TPO. Works well.

ChrisHelvey 01-22-2014 04:48 PM

Thanks for your response. So, you started in the center. That makes sense. Do you use the PTO primer on the bottom side of the roll too, or just on the top where you use the tape?

1985gt 01-23-2014 11:27 AM

The primer is only for the tape. Get a cleaner also. Clean, prime then stick the tape and roll it in with a neoprene roller. The glue goes on the substrate (plywood) and the sheet also.

ChrisHelvey 01-23-2014 12:18 PM

Do you have a recommendation for a good PTO cleaner?

1985gt 01-24-2014 12:15 PM

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