New Decking

Unattended leaks from end the cap seams, one taillight fixture, one backup light, and deteriorated access door gaskets laid waste to the bathroom floor over time.

This composite image was taken just after most of the rotted decking was removed.  The inset image shows damage where the battery is normally mounted.

The aft-most 4X8 sheet of 5/8” decking was removed to cover the bulk of the repair while the damage in the battery area was cut back to good wood.

Severe aft decking damage can be addressed two different ways.  One method, known as the clamshell, involves removing all exterior metal at the frame/decking line, spreading the back of the trailer open, and sliding in a complete section of new decking.

Due to the placement of the battery area damage & my general uneasiness with the first method, I chose to do a two-piece repair placing the seam over the main frame C-channel.

The seam was later fortified with glassed-in steel dowels.

Since there was not enough good wood left to act as a template, a large sheet of cardboard was repeatedly trimmed until a good decking prototype was developed.

In spite of chamfering the edges of the new decking & covering them with duct tape (to both seal & cut down friction), a mini clamshell technique had to be employed since the shell was not happy about its current lack of structural support.

Here you can see a bottle jack supporting the shell at a rib while concrete blocks force the bumper (frame) down.

The next hurdle was figuring out what size the plumbing cut-outs were supposed to be around the dump valve.  I sent this picture out to everyone I could think of who might be able to help.  A special thanks goes out to Sneakinup & Overlander64 at the forums for their help.

Elevator bolts hold the new decking in place.

The seam between the old & new decking was scabbed from underneath with decking, polyurethane glue, and screws.

There is quite a debate as to what kind of product makes the most suitable decking.  I saw my reasonable decking replacement materials possibilities as either plywood or OSB.  Plywood subchoices consisted of interior, exterior, treated, or marine grade.  While I could bore you with details, the bottom line is that I had more confidence that OSB would last considerably longer with less damage if an undetected leak were to occur simply because of the manufacturing process.

 

Basically, since all the pieces of wood that make up OSB are sitting in a big pot of waterproof glue prior to being formed into sheets, the individual wood pieces are each sealed.  Not the case with plywood.

 

Treated plywood was not a consideration to me because most treatments are to keep insects from destroying the wood, and do not do much in the way of preventing rot.  It needs to be dry when before installation, and the sheets I saw for sale were wet, buckled messes.

 

In the "from experience" category, a friend built a house several years ago.  Needing one more sheet of OSB to finish sheathing a wall, he remembered a sheet he had left outside a year prior to cover something.  Retrieving it, only sun damage was noted, and he was able to use the entire sheet.  From my own experience, I knew that plywood would NOT have fared as well.

 

Then I read that the Airstream factory now uses OSB in the construction of new Airstreams.

 

The final kicker was that the home improvement store carried the 5/8 inch thickness that I needed.  So far, so good; I have no qualms about using OSB.