rubber roof replacement

Hi, 
Recently bought a 92 Gulfstream Class C and the roof needs help.  Rest of it is clean as a pin and well maintained.  The frt has been leaking where the metal frt joins and the thin luann is rotted but no interior damage.  I think the problem started because there is no solid part for the screws they used to attach the aluminum frt to the deck.  They were only screwed into the thin luann and foam.  I would do a localized repair but the rubber is also splitting down both side edges where they folded it over the side walls.  They should have took a sander and rounded the fiberglass.  Couple of small build details and the roof would still be good after all these years.  Given the cost of patch up and coating material, I'm planning on replacing the rubber.  I also never cared for patch jobs.  Luckily It is in my pole barn so I don't have to worry about weather during the process or how long it takes. 

The construction is aluminum framing with styrofoam blocks and luann glued over.  So at least no rotted framing to deal with.  Right now I'm planning to strip it down and replace the rotted sections of luann near the front.  Then I was going to put down another layer of 1/4" luann with construction adhesive so the rubber has a new smooth surface.

I was hoping someone else may have done this and could offer some pointers. 
Thanks

Take a look at the reroof project we did a few years ago, http://www.rvforum.net/miscfiles/RV_re-roof.pdf .  This will probably answer a lot of your questions.

Thanks, I think I may have run across the re-roof write up doing a google search.  A few questions remain. 

Adhesives used for the decking?  Liquid Nails covers many products.  Something that will bond but not attack the foam but still bond to the aluminum frame?  I was leaning towards a polyurethane.  To re-sheet over the existing luann, I would think plain construction adhesive would work?

Which would be better for a re-skin, luann or OSB ?  I know the OSB is more water resistant but isn't as smooth and heavier.

I'm seeing some sagging of the AC unit and frt vent over the cab.  I suspected rotted or sagging rafters but came to learn this has an aluminum tube frame.  The rear section appears to still be flat.  Evidently they didn't build in any pitch.  Only thing I can think is the aluminum has sagged from age and fatigue.  I was thinking of trying to jack it up with a pole jack inside but what will make it stay?   

Thanks again.

Why do you think the a/c sagging implies frame damage? The a/c just sits over a 14x14 hole in the luan, so a rotted substrate is going to let it droop. If you were thinking they actually framed that opening with metal girders, that probably isn't so unless the convenient a/c opening just happened to line up with one.

I would use any decent grade of wood-like panel for the substrate, Luan, pine plywood, OSB, whatever I could get at a decent price in the thickness I needed.  Yes, RV roof construction is light duty. Most everything just screws or glues to the substrate, and it's mostly too think to provide really good holding. The type of screw (head and thread style, diameter, material) and your technique is crucial to a good holding.

Actually they did but it appears to only be 1" sq tube and not very thick wall.    There doesn't appear to be any rot in this section.  I'm sure I will learn more as I dig further. 

BTW, having a tractor with a frt loader made the AC removal much less dramatic. 

That would be typical RV structure. Sidewalls may be the same, or maybe 1.25" square tube.

If you have an actual aluminum frame for the a/c opening, cross-connected to the lateral tubes, count yourself lucky. Often they just stiffen the luan with 2x3 or 2x4 around the opening.

I found this on their website.  http://www.gulfstreamcoach.com/quality.htm

Seems to be how this one was built even back in 92. 

I got the rest stripped off today.  Awning, side trim, vents, skylight etc.  Figured that was the hard part until I started trying to pull the rubber off!  Ugh!

I'm also not having any luck finding 1/8 luan around here. 

An update.  We succeeded in getting all the old rubber off.  I scored it into strips and it still took two of us, my wife pulling and me pushing with a wide putty knife.  I had set it out in the sun for a couple hours which I think helped some.  We were both wore out when it was done !

I'm off to Home Depot today as they say they have 1/8 luan even though the website says they don't.  Once I get the damaged section in the front repaired, I plan to re-skin the whole roof with fresh sheeting.  My new dilemma is what adhesive to use for this since most of it is still covered with the rubber glue.  I bought a tube of Liquid Nails Subfloor and Deck and guess I'll just have to do an experiment with it.

1/8" is the skin thickness? I would have expected 1/4".

1/8"? wow that thin stuff, think i would substitute for fiberglass reinforced plastic (FRP) lot stronger and will not rot.

Subfloor and deck glue is always used in conjunction with fasteners. By itself its not the best choice. Though it strengthens a decking system one of its main purposes in home construction is a sound deadening device. No more floors creaking or loud high heals.
If you are applying Luan to Luan I would drag a bead trowel over it or you would get a lumpy appearance. A thicker decking you shouldn't have to worry. Luan and strength are two words that don't go together. The manufacturer was really pushing the engineering envelope. In home construction it was only used for soffit, door construction or cabinet backing. Anywhere you need pretty but not strength. I would use 1/4" or 3/8" AC plywood which has a smooth finish on one side. Some stores carry lower grades with the knot holes patched. That would be cheaper if you can find it.  CDX is usually in thicker plywoods. It would give you a good surface to attach the rubber roofing to and strengthen the roof at the same time. The weight difference shouldn't be a deal breaker. You definitely want a water based or low VOC adhesive if styrofoam or plastic is involved. LiquidNail Heavy Duty is a low VOC strong adhesive. It's not recommended for floor decking because it's not as good as Subfloor and Deck glue for sound deadening. Strength wise it's great and considered the green glue.

How far apart are the metal tubes?

Thanks, I picked up a tube of the HD and testing it on some scrap pieces that were torn off.  The construction was very sturdy and light but dependent on the adhesives holding the luan, foam, aluminum frame both ceiling and roof.  Once the luan got wet and separated, structural integrity was lost in that section.  Getting a good bond is going to be key to restoring the strength.

There's a vendor on the MS Gulf Coast that sprays on a leak proof roof and they offer a lifetime no leak guarantee.  Check them out at www.noleakrvroof.com 

Moving along on this project.  I ended up primarily using the Liquid Nails Heavy Duty.  Thanks Mitch for the tip.  I tested it on a piece of scrap that had the rubber cement and a square of OSB.  It takes a day or so to get full strength but after 24 hrs the OSB was breaking when I tried prying apart the pieces. 

The water damaged section was the biggest challenge.  I started with a piece of 5mm" underlayment plywood for the ceiling.  I used Fusor Composite Adhesive (an Epoxy) to glue this to the aluminum framework.  I have used this stuff repairing Corvettes and this ceiling will never come loose! I used several small scissors jacks and planks to push this up in place for a tight fit.  I also used one with a 4x4 and another plank under the AC area for support and take the dip out.

The next day I glued in the Styrofoam blocks from on top using the Liquid Nails.  I removed the next 4' section of luan back as it was damaged on both sides and I wanted it to be one piece.  I ended up using 3/8 actual 11/32 plywood for the two front sections that were completely replaced.  For these I used a combination of the Liquid Nails for the foam and a bead of Locktight PL (urethane) on the aluminum framework.  I then finished the rest of the roof with the 5mm (7/32) underlayment over the existing 1/8 luan using the Liquid Nails.  The combination of material ends up the same thickness with no step in the decking.  I used some #8 self piercing screws along the edges and seams.

Few things I added.  In the front where the aluminum nose meets the roof is a joint with a trim piece caulked and screwed down to the roof.  They relied on fastening this with screws into 1/8 luan and Styrofoam!  I routed out the sections of foam and glued in some 3/4" pine about 4" wide.  Now that the 3/8 is all bonded over top, I have some meat to hold screws.  I also ripped up some 1x1 pine and glued it in the gaps between the foam blocks so that now the aluminum frame is bonded to the roof and ceiling in all areas.

Another thing I found was in the AC opening.  This thing has 4 longitudinal s of 1 X 1 1/2 tube and 1x1 tubes running crosswise on top of the longitudinal s.  For the AC support, they doubled the 1 x 1s which was a good idea.  But then the dummys cut clear through them, in the middle, with a hole saw to run the wiring.  All that was left is the bottom of the tube!!  After I jacked this area up to a slight crown, I used Fusor metal adhesive to bond a section of 1/8 x 1 1/2 flat on top.  Combined with the 3/8 plywood bonded on top, I'm hoping this adds support for the AC.  In any case, it's better than what Gulfstream did.

So today I'm going to try and fix a small section where the fiberglass siding  has come loose.  The luan has apparently come apart from the water getting in on top.  I bought a quart of thin epoxy made for fixing dry rot.  I can pour it in on top and hold the siding in with some jacks.  If it doesn't work, I'm not going any further.  It's mostly a cosmetic issue.  Next up is sanding the edges and generally going over everything to get ready for the new rubber.

Thanks for the report. You've been working hard!!!

Yes, I can see why it costs so much to have this sort of work done.  It is a lot of work!  My biggest problem is I am very uncomfortable more than a couple feet off the ground.  I spent yesterday putting up scaffolding.  My late father was a DIYer too and was into woodworking.  I've been making use of a lot of his tools.

I think you are doing a much superior job vs what an RV shop might perform.

Thanks Gary, I'm trying.  It's a very nice coach otherwise.  Interior is very pretty and like new.  So I think it's worth the effort.

One thing that is a little puzzling is the old roof material is white all the way through.  According to what I've read, that means it would be TPO.  But I didn't think they used that back in 92??  In any case I decided to go with the DICOR EPDM system.  It will be stored indoors as long as I own it anyway.

Maybe Alpha brand EPDM? The Dicor product is the stuff with the black substrate. I've never seen any similar statement about Alpha Systems EPDM roof material..

Well whatever it was, it's gone in the trash now. LOL  Fedex brought a big heavy box with the new rubber in it this morning.  Looks real nice and can't wait to see it installed.