Fixing roof

[Oilman04957]

Was wondering if anyone has ever use 4x8 sheets of pvc instead of Luan plywood any problem with it it same thickness just think.it would hold up better cause water would never hurt it and Delaminate. Any help would be great

[US1]

I would think the heat would play havoc on PVC, plus glue wont stick to it.

[Sweetbriar]

What are the load bearing properties of PVC sheeting as compare to Luan or lite ply? Could an owner still walk in a roof with a PVC based substructure or will additional support be needed?

My preference would be to stay with ply but to also water seal it with oil based paint or thinned epoxy.

[Oilman04957]

What's the best glue to use on plywood to plywood and what can I use for transition from roof to wall have 18 inch piece of fiberglass that bend to make curve and where can I get it mine has to many breaks

[hattitude]

Originally Posted by Sweetbriar

What are the load bearing properties of PVC sheeting as compare to Luan or lite ply? Could an owner still walk in a roof with a PVC based substructure or will additional support be needed?

My preference would be to stay with ply but to also water seal it with oil based paint or thinned epoxy.

It's not cheap, but it works great.... Smith's Penetrating Epoxy.

We used it in the marine world to repair/strengthen damaged wood, when removal/replacing the wood would be a major job... it soaks into the wood and basically turns it into a piece of fiberglass... It's only achilles heal is that it needs protection against UV ... So if in the sun, it needs a coat of paint.

I used it on a 3' section of wood frame, to my fiberglass flybridge, that had been damaged by termites... It was hollowed out a bit and thin in areas form the termites. I saturated it (multiple coats) with Smith's penetrating epoxy, fuilled in some voids with wood filler, then covered it with bilge paint even though it was never going to see sunlight...

When I sold the boat 5 years later, the repair looked like new and was rock solid..

I also used it to saturate the wood base to my 120 gallon bait tank. It too was painted, although in the bilge... and when I removed the tank 8 years later for an upgrade, the base was also like new...

It would probably be expensive to coat the wood substructure of the entire roof of a large motorhome, but there must be cheaper, similar alternatives.

That epoxy coating would make one solid roof....!

[Wbago97]

Can you post pictures of your project?

[Oilman04957]

Here some pics of my 1999 hareny couch roof repair

[Dav L]

Originally Posted by Oilman04957

What's the best glue to use on plywood to plywood and what can I use for transition from roof to wall have 18 inch piece of fiberglass that bend to make curve and where can I get it mine has to many breaks

Construction adhesive. You don't need any expensive epoxy resin. A couple $8 tubes of construction adhesive from Home Depot and you will never get two sheets of plywood apart once cured.

Replace the bad wood. Don't try to restore it. Just not worth the time or material. Job will come out better and cleaner. Just measure before you hack the old stuff up, Wonder Bar the old piece out, replace any wet insulation underneath, run any new wires needed, take some pictures of where things are (use a tape measure as a reference point), mark all ceiling joists on center, and glue and lay the plywood, snap lines for the joist centers, screw the new plywood in place. Seal the seams. Recover and seal. Go RVing.

[Oilman04957]

Isn't a spray adhesive better for more contact

[Oilman04957]

Originally Posted by Dav L

Construction adhesive. You don't need any expensive epoxy resin. A couple $8 tubes of construction adhesive from Home Depot and you will never get two sheets of plywood apart once cured.

Replace the bad wood. Don't try to restore it. Just not worth the time or material. Job will come out better and cleaner. Just measure before you hack the old stuff up, Wonder Bar the old piece out, replace any wet insulation underneath, run any new wires needed, take some pictures of where things are (use a tape measure as a reference point), mark all ceiling joists on center, and glue and lay the plywood, snap lines for the joist centers, screw the new plywood in place. Seal the seams. Recover and seal. Go RVing.

Do you need to weigh it down cause roof is slightly curved or crowned

[Dav L]

"Isn't a spray adhesive better for more contact"
No. not strong enough. Remember, construction adhesive is used to build houses. And the wood will break before the bond breaks.

"Do you need to weigh it down cause roof is slightly curved or crowned"
Depends...what are you using the adhesive for? To glue the plywood down to the joists? If so, what material is the joists? Wood or aluminum? If aluminum, use SikaFlex adhesive. And, if you aren't screwing the panels to the stringer, then yes, you will need to weight the panel down so that the glue can dry to hold the plywood to shape of the joists.

[arcaguy]

Originally Posted by Dav L

Remember, construction adhesive is used to build houses. And the wood will break before the bond breaks.

The adhesive manufacturers may make this claim but I don't believe it for a minute. I removed probably 200-300 feet of cedar wainscoting from an apartment building that I own and I generally pulled it off with my hands. It had been put up with construction adhesive. I don't know what kind and I don't know how long it was there. This was put up over drywall and most of the time the drywall was left intact. When I wanted to reuse some of the cedar I was able to scrape the residue off with a 3" mud knife. This was in a climate controlled environment, not on a roof that probably reaches 130* F or more. Personally I would use some type of mechanical fastener, or an adhesive specified to bond wood to whatever the substrate is and rated for 150* F or more. I'm sure others will disagree, I can just relate my experience.

[Dav L]

Originally Posted by arcaguy

The adhesive manufacturers may make this claim but I don't believe it for a minute. I removed probably 200-300 feet of cedar wainscoting from an apartment building that I own and I generally pulled it off with my hands. It had been put up with construction adhesive. I don't know what kind and I don't know how long it was there. This was put up over drywall and most of the time the drywall was left intact. When I wanted to reuse some of the cedar I was able to scrape the residue off with a 3" mud knife. This was in a climate controlled environment, not on a roof that probably reaches 130* F or more. Personally I would use some type of mechanical fastener, or an adhesive specified to bond wood to whatever the substrate is and rated for 150* F or more. I'm sure others will disagree, I can just relate my experience.

And I just tried to pull up some underlayment that was construction glued to some chip board in my RV and it pulled the chipboard top off.
Not sure what adhesive you had. Also, keep in mind that if applied to a smooth surface, not nearly the same amount of bite. I suggested Sikaflex to aluminum for just that reason.

The OP needs to provide clear details on what he / she is doing and what the materials are.

[Oilman04957]

So I'm not planning to rip off all wood just down to the layer you see in second pic so except for 1 sheet glued down to white Styrofoam all others glued to plywood