leaks...

[joel_newton]

Discovered several major leaks in the bus during our brief monsoon season (CA – now back in drought mode).  The original window areas have been covered primarily with three 4'x10' sheets of aluminum.  Likely suspects for the leaks are the roof and three horizontal seams.  The seams include the gutter line, the sash line, and the belt line.  From what I can see of the exterior walls from inside, water seems to be coming in primarily at the sash line.

I've pulled the sash line molding and mounting channel.  It looks like the mounting channel was originally set in black butyl rubber caulk.  It mush have failed and a layer of white rubbery caulk (butyl?) was added.  It was adhering randomly to one side or the other.  The mounting channel was conveniently funneling water into the horizontal seam between the sheets of siding at the sash line.  I haven't pulled the belt line or gutter line yet as that would undoubtedly invite a rain storm.

I know the proper way to fix the leaks would be to completely remove the panels, remediate the steel frame rust, put down new bedding material/double stick tape and reseal the exterior of the seams.  Not gonna happen.  I'll see what I can squeeze under the panel edges, then seal the exterior of the seam.  I am a fan of Eternabond products.  If the steel frame can be cleaned sufficiently some Eternabond 1" DoubleStick between the frame and panel then – 1" DoubleStick covering the seam overlapping BOTH panels and under the mounting channel. 

The question I have is – the mounting channel (with a single row of screws down the center) was screwed through only the top of lower siding panel.  I'm thinking this row of screws should at least be screwed into the seam.  This would put a little more pressure on the caulk against both the upper and lower panels preventing separation.  Perhaps a double row of screws – one into the upper panel and one into the lower panel would be better yet?

Is there a downside to doing this related to thermal expansion and contraction?  If you can skin a bus with a single sheet of aluminum I wouldn't think pinning down all edges of a ten foot length would be an issue??  Any thoughts???

[ol713]

      Hi;
     Need more info.
             What kind of bus?
             Gutter line I would guess is drain channel just above windows.
             Sash line I assume is just below the windows.
             Is your bus a shell or complete conversion?
                                           Merle.

[joel_newton]

It's a Dina complete conversion.  And, you are correct, gutter line covers seam between panel covering windows and roof, sash covers seam between panel covering windows and original siding and belt line between original siding and luggage compartments.

[joel_newton]

Back to the drawing board.  I was just digging out the caulking from the butt joint behind the sash line and discovered there is virtually no horizontal rail behind the bottom edge of the upper panels - perhaps 1/8" at best.  There are vertical frame members about every two feet  Perhaps fastening the bottom edge to them would help stabilize the panels.

There is a lot of rust and moisture in the caulking I'm digging out.

Any ideas?

[bevans6]

Sometimes you just have to take it all out, take it all off and start over.  Or - and this is sometimes the legitimate option - give up and scab over it, and use it till it falls apart.  Eternabond may well become your best friend.  Without being able to see what you can see, it's impossible to offer more.  Luck!

Brian