I finished the “drivers side” roof project. After inspecting the passenger side I’ve decided it doesn’t need repaired. I’ll just remove the old rain gutter caulk and put on new dicor above the rain gutter. My fix for the driver’s side took about 9 hours. This was not a particularly difficult project as I expected, but it was intimidating at the beginning. I’m guessing about 200 trips up and down the ladder.
The root cause of the problem was (and still is), the plywood decking material isn’t long enough to reach completely across the roof, from vertical wall to wall. On the passenger side of the roof, the decking material touches the top of the wall. On the driver’s side, it stops about 2” short of the wall and creates a 1” gap between the wall and the roof decking (see Photo 1).
Observations when uncovering the problem before repair.
The water-based contact adhesive that bonds the TPO to the plywood deck was still tacky. Not dried out as I expected. I did apply new Alpha contact cement to both the underside of the TPO and plywood and the gorilla tape I added. It needs to dry for about 30 minutes before you press the two surfaces together. This stuff is very sticky after it begins to dry. Very difficult to wash off. I was wearing neoprene gloves and got it on my finger. My fingers would stick together and tear the gloves trying to pry my finger apart. Very good stuff.
The plywood decking apparently come is 4’ x 8’ sheets and for my trailer somebody cut them a little to short. I have roof trusses about every 16” and there are a few screws in the decking (plywood) every now and then to hold the decking to the metal trusses. Where the plywood panels meet on a truss there’s several screws in each panel. Over the top of the screws is a webbing tape that I suppose is supposed to protect the screws from rubbing the TPO. Not sure how much good it does since the flat head screws are put in at various angles and the edges actually contact the TPO. I need to be way more careful walking on the roof.
Photo 3: I found a string of 15 holes where a tree branch rubbed the roof and pulled the flashing back on the LR corner of the roof. When I lifted the material, I could actually see daylight through these holes. I noticed this scrape a few months ago and examined it but I really didn’t think it had punctured all the way through the TPO. Next time I see something like this I’ll have to probe it with an ice pick to see if it penetrates. Fortunately I found this before any long term damage had occurred.
Things I learned:
The rain gutter is held on by a screw every 6” and backed by butyl tape. Of the 80 or so screws I removed two were broken off at factory installation because they were drilled into steel. I suggest you have a dozen or so self tapping screws in case you run into the same problem. I needed two self tapping screws. I relied on the new butyl tape to seal the old screw holes and I just drilled a new hole about ½” from the old hole.
For cleaning off the old butyl, the TPO and old dicor I used Xylol. It worked way better than acetone.
Reinstalling the gutter: you may need an ice pick to help locate the old screw holes. Once you get the rain gutter started the holes line of pretty good, but occasionally I had to fish around with the ice pick to determine the angle of the hole.
It didn’t occur to me to use blue masking tape to tape off the top of the rain gutter when I re-caulked the top of it with dicor. If I did this again, I’d tape the rain gutter, apply the dicor then remove the tape.
The dicor is very messy. I discovered you can run a bead of the “dicor for vertical surfaces” (not the self leveling) then spray some alcohol on your finger and easily spread the dicor sealant and shape it and it doesn’t stick to your fingers. I had to keep spraying my fingers but this was very helpful.
Using a heat gun on the rain gutter made removal pretty easy. Later I set up sawhorses and used the heat gun to remove the butyl from the back of the rain gutter. Heat the gutter material, not the butyl. I cleaned the gutter with Xylol, spray painted it black since it was looking pretty faded, then applied new butyl tape. Leave the white backing paper on the butyl tape until you’re ready to actually insert a screw in that hole. It’s not possible to line up all those screw holes at the same time so leaving the white backing on lets you make adjustments as you work. Then, gently slide the backing down and insert a screw.
The repair:
I put on three layer of gorilla tape to pull down the decking that was lifted and to fill the gap and connect the side to the roofing deck. This is not a great fix, but it’s better than it was. Today I stopped by a roofing supply store to ask about what might adhere to TPO and offer a little more protection against scrapes. TPO material is commonly used on roofs of commercial building, so they have an array of products. Also, TPO has the lowest surface energy of all roofing products (which means almost nothing will stick to it). It’s surface energy rating is half that of glass. I put a link to an interesting article about adhesives/tapes at the end of this writeup if you’re interested.
The guy at the supply house suggested I put metal flashing over the top of the TPO to cover that 2” gap. That’s a great idea. I’ll have to consider if I’m willing to pull the rain gutter off, install the metal flashing, reinstall the rain gutter and then cover the flashing with Eterna bond. But that’s a very good idea and I wish I had thought of that before I started. I think I’d put the flashing over the top of the TPO rather tan under the TPO. I’ll wait and do this another time. Any thoughts?
Article about adhesives for “low energy roofs like TPO and EPDM:
https://www.adhesivesmag.com/article...%20like%20TPOs.
That’s it, on to the next project: why are my traction light, ABS and Brake like flashing on and off?
Happy Camping,
Dustin
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