looking for advice.

[Freebie]

Hello fellow old RV builders. I am looking for some advice and making sure I am headed in the right direction. I am getting close to putting the top side of my roof on Freebie. I am on the fence as to what to use. I was at my favorite home store(Home depot) and told one of the guys there what I was doing and asked what he recommended to put on the top of the roof. I told him I wanted something thicker than the Luaun that was previously on there. He suggested using OSB board. I asked if it would hold up to the elements and he used the analogy that its used to wrap the out side of houses and roofs before the shingles and siding why not? My question is is he right or should I just go with the 3/8" ply wood that I originally had in mind? while the OSB is a lot cheaper I want it done right more than I want it cheap. Help me out before I make a bad decision.

Thanks

[Freebie]

Hello fellow old RV builders. I am looking for some advice and making sure I am headed in the right direction. I am getting close to putting the top side of my roof on Freebie. I am on the fence as to what to use. I was at my favorite home store(Home depot) and told one of the guys there what I was doing and asked what he recommended to put on the top of the roof. I told him I wanted something thicker than the Luaun that was previously on there. He suggested using OSB board. I asked if it would hold up to the elements and he used the analogy that its used to wrap the out side of houses and roofs before the shingles and siding why not? My question is is he right or should I just go with the 3/8" ply wood that I originally had in mind? while the OSB is a lot cheaper I want it done right more than I want it cheap. Help me out before I make a bad decision.

Thanks

[UFO Pilot]

I recently used 1/2" OSB to make a floor in my attic. I used it because it was cheaper than plywood. I am sorry I used it as it has very little strength at the seams. My rafter spacing is 24". I don't know if that is a factor in your project or not.

[Wallaby Dan]

Ken, You can't stand on felt and As I understand it you probably should use 3/8" ad plywood over the rafters and then put down the metal roof?? and recoat whatever you do put down. I assume you are reusing the metal and that is ok as long as you find any and all holes and button it down really good! Use a fiber patch if you have a rip or tear and then coat with kool seal or a rubber compound that makes a roof seal completly I havve heard that there is a liquid rubber membrane that rolls on and drys like a rubber EPDM. I never used it but have heard of it and If you can find it ,I would use that. Thats me but ya asked! Good luck and let us know how it goes,

[fleamarketer]

Ken,
I terms of what to use under your metal roof I can't help you much because as I have said in my MH there are only luan ceiling and medal roof bows.But in terms of what to use to reseal your roof,Kool roof has a 5 yrs garenttee and Snow Roof Systems has a 10 yr.Both are onwed by Sherman Williams.With Snow Roof Systems you primer with their primer and seal tape the seams and primer over that and then apply 2 coats of their roof coating which is a rubber coating.It is a very thick so it doesn't go very far.The price I got for the roof coating was $31.99/gal with over 5gal's needed to to a 20' roof.All and all with the primer,roof cement,seal tape,and coating the price is alittle short of $500.With the roof coating you don't want to run short on in the middle of the job given the type of rubber coating it is,so
buy more than you think you need.Lorna told me about this system and in my mind it is the only way to go.

[machman72]

IMHO, and this is coming from 20 years of commercial construction experience, I personally would use 3/8 or 1/2 treated plywood. OSB is ok for walls , because if water does get on it, it is going to run down, and out. CHEAPO houses, use OSB for their roofing. Quality builders use 5/8 plywood. That is too heavy for your trailer roof. If OSB gets wet, it swells and starts to flake apart. RV's and travel trailers are subject to constant flexing as we move them up and down the "perfectly glass smooth highways we travel" . As such, the seams and joints are subject to opening up at some point and letting moisture in. If you use the treated plywood, even if you do eventually experience a leak, you do not have to worry , that now you got to tear it apart to fix the wood. The treated will out last the rest of the trailer.

[Bob&Pat]

I like Steve's (machman72) idea. Treated plywood would outlast the motorhome.

[Freebie]

I think that is the route I will take. I wanted to be certain before I did though.

Couple of things. I have a rubber roof on the rig. I plan to use eternabond on all the edges and places where it has an opening (Vents , A/C etc.) I do want to use something like kool kote to put on it after I am done to be certain it's fixed and sealed. I will look in to that as well.

Thanks for the info.

Also who is KEN?

[Wallaby Dan]

Ken, If you have a rubber membrane roof, You have to make sure you don't use anything that has Petroleum or oil based sealers!!! The oils in them will destroy it!
The dealers say to use Lap Sealer and that is it! No silicone whatever!!! They really stressed this point! That is what is going on mine. To tell you the truth, I would think that roof had already been replaced already as most rv's had Metal for the roof.
You can use the treated plywood or use AD exterior glued plywood. They used that on mine with 3/8" thickness. Also they sand it with something that makes the rubber glue stick better! I don't know what kind of sander it is but it takes enough of the wood that it has little,[1/16"] groves in the plywood. You use a special glue to hold that rubber roof down. Then you use the lap sealer on the seams and edges. Good luck and show us how it is going!!

who is Ken???...Look at your sig, Says Ann and Ken???? Sorry, I took my glasses off, Keri . It looks like Ken with the glasses off! Did I say I was old....55 Today.... yeah that...

[Freebie]

ok I will have to look for the glue for the roof then.

Oh btw that's A R I N & K E R I Me being Arin.

it's ok to be old just dont' tell any one.

[NeilV]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freebie:
Hello fellow old RV builders. I am looking for some advice and making sure I am headed in the right direction. I am getting close to putting the top side of my roof on Freebie. I am on the fence as to what to use. I was at my favorite home store(Home depot) and told one of the guys there what I was doing and asked what he recommended to put on the top of the roof. I told him I wanted something thicker than the Luaun that was previously on there. He suggested using OSB board. I asked if it would hold up to the elements and he used the analogy that its used to wrap the out side of houses and roofs before the shingles and siding why not? My question is is he right or should I just go with the 3/8" ply wood that I originally had in mind? while the OSB is a lot cheaper I want it done right more than I want it cheap. Help me out before I make a bad decision.

Thanks </div></BLOCKQUOTE>

Marine plywood is what would I would use. PT plywood tends to blister and crack.

[Wallaby Dan]

Sorry arin, I'm 55 going on 555 today! Some days I feel even older...

[fleamarketer]

The use of a treated plywood,any health concerns because the roof gets hot?.

[Lorna]

The PT Plywood would be awfully heavy. The OSB would be okay. OSB is more stable than plywood (less chance of warping and/or plies seperating). It cannot withstand continuous water but an occasional leak will not hurt it. OSB will have a rougher surface. I assume you are placing the metal roof (glued down with contact cement) over the OSB. PT plywood tends to warp BADLY. I would be greatly surprised if you can find any that is flat to start with. Yes, PT plywood will hold up better than OSB under wet conditions. ALso the flexing is a possible factor. BUT there is really nothing to keep the PT plywood from warping. The exterior roof skin and roof coatings are not enough to keep it flat. You need to decide the best material for your use. Personally I would go with OSB.

BTW, This is all from David who has 37 years construction experience (Residential & Commercial... new construction, rehabs, remodels & restoration).