Installing a new sub floor...

[SeanL]

Is there any need to leave an expansion gap where the new sub-floor meets the wall in my Airstream? I plan on removing the old sub-floor and repalcing it with new 3/4" plywood that I will seal before installing my floor covering.
Thanks for all the help!

[worldinchaos]

Is your existing subfloor so rotten that you can't use it as a template? If not I would just use exactly the dimensions that are existing. In fact that is what I did in my replacement.

You have to remember that your metal walls will also expand with heat, albeit at different rates of expansion.

However for whatever the info is worth from one 1959 trailer, my new floor cut exactly to old dimensions had a 1/8" to 3/16" gap on the sides and was flush on the curved ends (and yes I had marked where the c-channel previously was so this is not due to flex of the shell, at least not as a result of the rebuild--it could have occurred over 50 years).

[Melody Ranch]

Sean....the sub floor is designed to extend under the walls...which in turn are fastened to the floor and frame together. I suggest you kick back and read some of the floor replacement threads here. UNLESS, heaven forbid, you plan on screwing a 3/4 in plywood floor on top of the rotted old floor. In that case you would probably need a small expansion gap.

[overlander64]

Greetings SeanL!

Welcome to the Forums and the world of Vintage Airstream ownership!

Originally Posted by SeanL

Is there any need to leave an expansion gap where the new sub-floor meets the wall in my Airstream? I plan on removing the old sub-floor and repalcing it with new 3/4" plywood that I will seal before installing my floor covering.
Thanks for all the help!

I am not absolutely certain that I completely understand your project, but if my understanding is correct, you may be attempting a repair that will become a future headache.

My impression is that you are attempting to repair floor rot, and overlaying the existing floor is not a good plan. Your Airstream has semi-monococque construction meaning that the floor, body, and frame work together as a unit. When the wood floor fails and needs to be replaced the process is somewhat involved . . . in fact, for a total floor replacement, it is often recommended that the body be completely separated from the frame; although, it is possible to completely replace the floor without doing so with some extra planning and piecing of the floor segments.

When the floor is replaced, the lower section of the interior walls is removed by drilling out the pop-rivets that attach the aluminum to the wall structure. This process reveals the channel at the base of the wall where the wall sections are attached to the floor and frame. It is necessary to access this cavity to release and remove the original floor (or what remains of the floor) - - then the new floor is inserted under/within the aluminum channel and the attaching hardware is reinstalled. There are a number of threads here on the Forums detailing the floor replacement process -- try Forums searches for floor replacement or full monty - - you will find many different approaches to the problem.

On the other hand, if you are just wanting to prepare your coach's sound floors for new floor covering, you would want to proceed with something less than 3/4" plywood as you would not want that much additional weight when the payload capacity is not huge. My Overlander had sound floors, but the original plywood had numerous imperfections so my sheet vinyl installer insisted upon a new luan underlayment prior to his installation - - smoothed up the floor and resulted in a beautiful job.

Good luck with your project!

Kevin