Common roof leaks - 1996 G30 Blue Bird

[cwatkin]

I recently bought a Chevy G30 short bus (12 ft body) that was partially converted. I pretty much tore everything out and am glad that I did. I found leaks from bad caulk as well as mistakes the previous guy made. I have sealed all those up. I also tore out the entire floor and the sidewalls which allowed me to find leaks I never would have found otherwise. I pressure washed the floor, applied a rusty metal primer, and then coated it with tractor paint. I plan to glue down EPS foam insulation and top with plywood for the floors. I plan to put XPS in the walls.

The bus is a lot drier now and I thought the leaks were gone. I am seeing some water in the sidewalls and cannot tell where it is coming from. I sealed the windows so figured it might be from the roof. Is this a common issue. There are rivited seams but no skylights or escape hatches. It is a 1996 G30 Chevy chassis with a Blue Bird 12ft body as measured from behind the driver seat if that means anything.

I am new to this so where should I be looking? I am about ready to start reconstructing the inside the way I like but want to take care of this fundamental problem first.

[Crisfole]

I ran a bead of automotive sealer across every seam on top of my bus. Now all that's left for sealing is the windows and maybe the sides, but they are double walled, so I'm not too worried there.

One thing that does cause tons of moisture is condensation. Is the bus you're working on well insulated?

Cold metal is a great condensation point for relatively warm moist air. On a particularly humid day it rains in my bus. I want to get a few more exterior things done before I spray it though.

[musigenesis]

Originally Posted by cwatkin

I recently bought a Chevy G30 short bus (12 ft body) that was partially converted. I pretty much tore everything out and am glad that I did. I found leaks from bad caulk as well as mistakes the previous guy made. I have sealed all those up. I also tore out the entire floor and the sidewalls which allowed me to find leaks I never would have found otherwise. I pressure washed the floor, applied a rusty metal primer, and then coated it with tractor paint. I plan to glue down EPS foam insulation and top with plywood for the floors. I plan to put XPS in the walls.

The bus is a lot drier now and I thought the leaks were gone. I am seeing some water in the sidewalls and cannot tell where it is coming from. I sealed the windows so figured it might be from the roof. Is this a common issue. There are rivited seams but no skylights or escape hatches. It is a 1996 G30 Chevy chassis with a Blue Bird 12ft body as measured from behind the driver seat if that means anything.

I am new to this so where should I be looking? I am about ready to start reconstructing the inside the way I like but want to take care of this fundamental problem first.

I pulled about ten rusty brackets off the bottom of my bus and did some rust remediation experiments on them. One of the best (and easiest) results came from scraping the loose rust with a paint scraper, thoroughly cleaning and then painting with two coats of rustoleum rusty metal primer and a coat of enamel. This is not a complete treatment of the rust (since this still leaves some rust embedded in the paint layer) as with Ospho but it seems to work fine anyway.

Can I ask why you're using EPS on the floor and XPS on the walls? I'd expect it to be the other way around, since XPS has a greater resistance to compression (25 PSI vs. 10 PSI, as I recall).

[cwatkin]

I was wondering about condensation but it DEFINITELY isn't that after this weekend when we got all the rain. I think it must be coming from the roof. I was gone but ordered a quart can of brush in seam sealer once I looked inside and could see water pooled on the floor. I did not remove the ceiling but am starting to wonder if I should do so as my next step. I figure I will pressure wash the roof exterior to get it as clean as I can before sealing, then let it dry out for treatment the next warm day.

The water seems to be coming down from inside the side walls and then running across the floor to where it pools in the back due to how the bus is parked right now.

The XPS foam I bought has a rating of 16psi. I had a choice of some lower strength EPS around 10-15psi and one rated at 25psi. I think you have it flipped or maybe it is just that way at my local Menards where I bought the stuff. I can definitely tell the EPS is a lot stronger stuff than the XPS.

I did just what you suggested with treating surface rust on the floor. I took a pressure washer and blasted out all the loose rust after removing the rotten wood and nasty rubber layer. I got it good and clean. I also removed any old bolts, screws, etc. that could be removed so that I could fill the holes. Anything too rusted in was cut off with an angle grinder and primed/painted over.

I then let this primer cure for several days with a small heater and gave a nice thick topcoat of tractor paint. I figure tractor paint will be good and tough. Once I get the leak resolved, I will insulate the floor.

I had started putting XPS in the walls but may pull it out to see where the leaks are coming from. I think the water must be running down from the roof as I caulked the windows nicely and don't see how any water could be getting in there. I also patched any of the holes the previous owner made or re-used them for electrical outlets as I plan to have separate 12V DC and 120V AC systems. The secondary heater core (rear bus heater) and associated tubing came out and I plan to re-use the holes in the floor to run 12V DC up from the engine. The previous guy had it run non-fused through a sharp metal hole in the side of the bus directly to the battery terminals! The first thing I did was disconnect that and I plan to tear it all out and redo it differently. I also bought marine/RV rated wiring and flexible conduit for that run.

Anyway, this is my first shot at converting a bus so want to do it right. Bare with me if I ask some dumb questions.

Thanks again.

Conor

[musigenesis]

Originally Posted by cwatkin

The water seems to be coming down from inside the side walls and then running across the floor to where it pools in the back due to how the bus is parked right now.

It's probably your windows leaking (not that the roof isn't also a source of leaks, and worth checking). Pretty much everybody has leaking windows, and the antidote is to remove them, clean them, and reinstall them with sealant of some sort.

Originally Posted by cwatkin

The XPS foam I bought has a rating of 16psi. I had a choice of some lower strength EPS around 10-15psi and one rated at 25psi. I think you have it flipped or maybe it is just that way at my local Menards where I bought the stuff. I can definitely tell the EPS is a lot stronger stuff than the XPS.

Around me Foamular-250 is the most common XPS and it's rated at 25 psi, with the EPS usually at 10 psi. I see that you're using your strongest material on the floor and that makes sense.

[cwatkin]

Sorry about the confusion. I got my insulation types mixed up. This isn't stuff I deal with on a daily basis but here is what I have actually purchased for this build. I plan to use the pink Foamular 250 in 2 inch thickness for the floor. I am using XPS and not EPS for the floor. This stuff has 25 psi compressive strength. I am using 1.5 inch thick foil-faced polyiso for the walls. This is the 16 psi stuff and not cheap. It has the best heat resistance and R value. There will be no EPS in this build as that is the cheap crap. The only EPS will maybe be a cheap cooler or bait bucket but this won't be used for insulation.

I also plan to use another layer of 1/2 inch polyiso between the wall ribs and my internal framing. Luckily I have only installed this in one location as I am thinking of removing all insulation before proceeding with the build to find my leaks. I understand you want as few penetration spots through insulation as possible to prevent condensation, etc. I may also make window blinds from scrap 1/2 inch polyiso for insulation and privacy over the windows when parked.

For now, I think I am going to pull the insulation out of the sidewalls. It should come out intact as I haven't glued it and I can cut any of the seams I had taped with HVAC tape and re-use it. I will then spray the bus with water and look for leaks. I was planning to do this today but it didn't sound fun spraying water in 32 degree weather with 50 mph wind gusts!

I am putting the rest of the build on hold until I seal the leaks. This isn't rocket science but I have never done it before so it is something new to learn and figure out. So far I have followed all advice and am glad that I did. I thought the windows were sealed up because I caulked around them but maybe they are not. My water test should tell. I can definitely tell my rate of leakage is greatly reduced but still an issue in heavy rain.

Thanks again,

Conor

[musigenesis]

My windows were leaking in a particularly evil way. The frame of the window is four separate pieces (top, bottom, left and right) pressed and screwed together, but the strong attachment is all in the inner part of the frame - the edges of the bottom part are held against the edges of the side parts just by the shape of the pieces. If the edges of the bottom part get bent slightly downwards, it creates a tiny gap that water just flows through.

Maybe post some pics of your windows and I'll see if I can identify what I'm talking about.

Polyiso is unusual stuff in that it's the only insulation (that I'm aware of) that actually has an R-value that increases with temperature (at least within the range of temperatures that humans deal with). This makes it better for insulating in hot weather, but correspondingly not quite as good in cold weather (below 60F). So for cold weather it's often rated the same as XPS foam.

[cwatkin]

I will get some pics. Sorry I have been SWAMPED with work and finally I have a nice weekend day where I am not busy so I did a little more looking into this. I am not saying the roof or windows aren't leaking but I put a water hose on top of the bus and found two very obvious problems.

1. The previous owner had put a window AC into this thing and had it built into a cabinet fully within the bus. It invited water in so I reinstalled it more like a normal window unit. Apparently my job wasn't any better so I am debating on pulling the thing out or building a solid metal awning around the thing.

2. The side handicapped door gasket is leaking and badly. Water was just pouring in and running down from the top of the door. I assume these gaskets are something anyone can replace. Should I just buy automotive door gasket or is there a better suggestion?

Thanks,

Conor

[EastCoastCB]

Originally Posted by cwatkin

I will get some pics. Sorry I have been SWAMPED with work and finally I have a nice weekend day where I am not busy so I did a little more looking into this. I am not saying the roof or windows aren't leaking but I put a water hose on top of the bus and found two very obvious problems.

1. The previous owner had put a window AC into this thing and had it built into a cabinet fully within the bus. It invited water in so I reinstalled it more like a normal window unit. Apparently my job wasn't any better so I am debating on pulling the thing out or building a solid metal awning around the thing.

2. The side handicapped door gasket is leaking and badly. Water was just pouring in and running down from the top of the door. I assume these gaskets are something anyone can replace. Should I just buy automotive door gasket or is there a better suggestion?

Thanks,

Conor

Depends. On my last bus the WC door seal leaked but it was out of production and unavailable.