RV roof replacement question

[sanchospencer]

Looking for advice on roof replacement. I'm renovating a 30ft Georgie boy swinger from the early 2000's. The roof is shot, and is the next big thing I'm tackling. I've redone the inside ceiling paneling, and added some extra wood support joists for some extra sturdiness. Ive got a brand new piece of tpo to lay on top, but want to buff up the roof as well. (I am aware of weight, although this RV will mostly be stationary) The plan is to peel away the old membrane, replace any bad spots of the 1/8 inch paneling with new paneling. Luan board seems like it's not really existent anymore, at least here in Canada, so likely use something cheap like revolution ply. Once I've got a level field, I want to add another 1/4 layer. Originally I thought marine grade, but at 150$ a sheet, there's no way haha. So now I'm thinking just cheap 1/4 pine. My question is, should I seal the exterior surface of pine with some polyurethane sealant or exterior sealer? I live on the west coast of Canada where everything is damp and wet a lot of the time. Any recommendations? My only concern is that the exterior sealant put on the wood, might not mingle with the tpo adhesive. Has anyone done something similar to this? Would love feedback and advice if there's any out there. Thanks!

 

[rvlifer]

Never did anything like that but i cant imagine extra protection can hurt as long as it doesnt impact the weight too much or interfere with gluing down the new membrane.

 

[Boat Bum]

If you're going to use cheap pine in a damp climate, I would absolutely seal the wood. I would use BilgeKote (that's a great price) based on experience. This paint is for the bilge in boats which is expected to be impervious to water.

You could easily paint a small piece of wood and test the TPO adhesion on it, I'd be surprised if you couldn't.

 

[sanchospencer]

If you're going to use cheap pine in a damp climate, I would absolutely seal the wood. I would use BilgeKote (that's a great price) based on experience. This paint is for the bilge in boats which is expected to be impervious to water.

You could easily paint a small piece of wood and test the TPO adhesion on it, I'd be surprised if you couldn't.

That's a fantastic idea. Thanks!

 

[CharlesinGA]

The Dicor adhesive I used to put down my membrane roof (EDPM) is water based and the wood must be fresh so the water in the adhesive can migrate into the wood. Otherwise the adhesive will never cure. I was told by Dicor that I either had to skin over my old roof with fresh wood or replace it. The water will not even migrate thru the old adhesive that is on the old wood. I ended up replacing the 3/8 OSB that Thor had installed, with 11/32 plywood screwed down.

There are a few pics HERE

Charles

 

[sanchospencer]

The Dicor adhesive I used to put down my membrane roof (EDPM) is water based and the wood must be fresh so the water in the adhesive can migrate into the wood. Otherwise the adhesive will never cure. I was told by Dicor that I either had to skin over my old roof with fresh wood or replace it. The water will not even migrate thru the old adhesive that is on the old wood. I ended up replacing the 3/8 OSB that Thor had installed, with 11/32 plywood screwed down.

There are a few pics HERE

Charles

Nice that looks so clean! Well done. Yeah that's a good point about the adhesion. @Boat Bum suggestion of using a bilge paint is good, but being an enamel, it most certainly could interrupt with the adhesion properties of the water based glue I'll be using. I'm thinking maybe spar urethane on the wood, since it is also water based. Or maybe it would be better just straight onto the ply. I'll have to do some testing I think.

 

[rvlifer]

If it were me i would be sorely tempted to spend the money on the marine grade. Costs more but still a lot less than having to redo the roof again or deal with water damage

 

[sanchospencer]

If it were me i would be sorely tempted to spend the money on the marine grade. Costs more but still a lot less than having to redo the roof again or deal with water damage

I've thought about it. But the price jump is incredible. 25$ per sheet=150$ as opposed to if I did marine 150$ per sheet=900$. It would be bomb proof for sure. Thing would outlive it the frame it's on. The cheaper way is, yes, cheaper, but should still last 10-15 years if maintained and done correctly.

 

[rvlifer]

I've thought about it. But the price jump is incredible. 25$ per sheet=150$ as opposed to if I did marine 150$ per sheet=900$. It would be bomb proof for sure. Thing would outlive it the frame it's on. The cheaper way is, yes, cheaper, but should still last 10-15 years if maintained and done correctly.

I dont disagree. The adhesive stuff is what made me lean that way. Seen too many rvs with the roof blown off

 

[John From Detroit]

If you're going to use cheap pine in a damp climate, I would absolutely seal the wood. I would use BilgeKote (that's a great price) based on experience. This paint is for the bilge in boats which is expected to be impervious to water.

You could easily paint a small piece of wood and test the TPO adhesion on it, I'd be surprised if you couldn't.

I would recommend the same Cut. Fit. Seal ALL SIDES.
assemble

Now why would you re-do the ceiling BEFORE the ROOF?

Or is this a garage job (With another roof above it? )

 

[sanchospencer]

I would recommend the same Cut. Fit. Seal ALL SIDES.
assemble

Now why would you re-do the ceiling BEFORE the ROOF?

Or is this a garage job (With another roof above it? )

This is my first RV project, and it actually originally wasn't going to be a full Reno. When I started I didn't know much about RV construction, and so one of the first things (first mistakes) I did was take out the ceiling since it was carpeted and I live in a damp coastal region. Little did I know that carpet and 1/8 paneling is essentially foundational in the RV world lol. After that I didn't have much of a choice but to continue and finish the ceiling since setting foot on top of the roof was now impossible.

 

[CharlesinGA]

Nice that looks so clean! Well done. Yeah that's a good point about the adhesion. @Boat Bum suggestion of using a bilge paint is good, but being an enamel, it most certainly could interrupt with the adhesion properties of the water based glue I'll be using. I'm thinking maybe spar urethane on the wood, since it is also water based. Or maybe it would be better just straight onto the ply. I'll have to do some testing I think.

The urethane will seal the wood also, same problem, water from the adhesive will have no where to go.

Charles

 

[sanchospencer]

The urethane will seal the wood also, same problem, water from the adhesive will have no where to go.

Charles

Yeah you are definitely right Charles. I think either straight wood (I will likely go fir 1/4 now instead of pine) followed by straight adhesive and tpo. Or, buy a solvent based glue, which would allow me to seal the wood as well, and tpo, since from what I can tell on the internet, solvent glue shouldn't need to be absorbed and rather evaporates.

 

[blw2]

If it were me rebuilding an RV roof, hands down I would go find an rvroof.com location and have it sprayed instead of putting down a membrane. I had mine done many years ago. Best mod I've done to the RV, no question.

 

[blw2]

oh, and if I weren't doing the sprayed flexarmor roof, I would seal the wood with pentrating epoxy (Home of Smith's Original and Genuine Clear Penetrating Epoxy Sealer)

 

[CharlesinGA]

solvent glue shouldn't need to be absorbed and rather evaporates.

Where would it evaporate to?

Charles

 

[sanchospencer]

Where would it evaporate to?

Charles

To the atmosphere. The solvent dissipates before the seal is made

 

[Kirk]

Or, buy a solvent based glue,

Make sure that the solvent-based glue will not damage the TPO. While some solvent-based adhesives are specifically designed for bonding TPO membranes, it's crucial to use adhesives that are formulated for TPO and compatible with the specific substrates to avoid damage or compromised performance.

 

[CharlesinGA]

To the atmosphere. The solvent dissipates before the seal is made

Doesn't work that way. The adhesive cures as it dries. If you apply the adhesive (be it water based or solvent based) and then carefully lay down the membrane and I used wide very deep pile rollers, to roll it down tight, the only solvent that might escape to the atmosphere is along the very edges.

The only adhesives that work as you describe are certain contact adhesives. They work best if BOTH surfaces are coated and allowed to cure to the point it will not come off when you "knuckle" it. You will NEVER get a full roof sheet of membrane down smooth and even using a contact adhesive.

Charles

 

[Onyrlef]

...you will NEVER get a full roof sheet of membrane down smooth and even using a contact adhesive.

Charles

" Never, ever".