New Walls & Funny Math

The Turtle-Heads following along have seen our battles with mold and leaks.  Because of this, the month of June had been spent pulling the old walls and framing out the wood and installing insulation for the new walls.  We have also gone through the entire outside of the coach and fixed all the leaks that we had.  It was quite a bit of work.  I was gone for most of July and the beginning of August for work but now I am back and we are finally in a place where some construction is happening again.  It’s a good feeling.  As of this past week we have started putting up the new walls but I’ll catch you up to how we arrived here.

Walls were thin, poorly insulated and leaky

The old walls on the drivers side were only cheap 1/4″ plywood screwed to the frame.  The passenger side walls were 1/2″ plywood, a little nicer, but also screwed directly to the frame.  The old walls were painted white and had some type of paper backing (I am guessing to hide the seams in the wood) and vinyl wallpaper on top of that.  We had some issues with the bus having a few leaks. (  Because of that there was some water getting into the coach and soaking through the wood.  It would get into the paper backing and then the vinyl wallpaper would prevent the water from drying so mold started to form along the walls.  It wasn’t pretty.  Once we found the mold under the wallpaper the decision was made to pull out all the walls, fix the leaks and rebuild with new walls on the inside of the coach.

Walls Pulled Out!

Pulling the old walls was a chore.  The 1/4″ wood on the drivers side came out fairly easy.  While some of the screws were rusted in, it was still simple enough to pull the wood right out over the screw heads.  Then going back afterwards and drilling out the rusted screws or taking them out with a pair of locking pliers (vice grips).  The 1/2″ wood on the passenger side was another story.  There were stainless screws and drywall screws and rusted screws of all types.  About half of the screws came right out. After that the battle was on. There were some screws that had filler over them which made them a little difficult to find.  Then you had to dig out the screw head and try and get enough of it to get the pliers locked on to the head.  Lots of chiseling and grinding, not fun.

Pulling the old walls was a bloody job

Proper use of electrical tape.










We are finding that in a motor coach it is common to have condensation form often and in various places.  With the AC on inside the bus and the hot sun beating down on the exterior transferring to the frame of the bus there is bound to be moisture at some point.  This is also commonly seen in the morning with the dew forming on the outside of the bus along the frame.  All of this had to be taken into account when rebuilding the new walls.  Below you see some of the surface rust that formed with the moisture in the walls.

Light rusted areas on the frame – all surface rust

Surface Rust sanded and painted!

To keep the walls lightweight and simple we decided to use 1/2″ plywood.  While it isn’t completely waterproof it was either this or Corian and with Corian at 300$ a sheet, the plywood won.  To battle the moisture I painted a coat of oil based primer on the outside face of the plywood and then coated that with poly-eurathane.  The idea behind this is to prevent any damage to the wood from moisture.


Many a fulltimer has told us if you are going to cut any corners, don’t cut it from the insulation.  Nothing is more important than being able to regulate the temperature inside the bus.  The tougher part was making the decision to lose another 1.5″ on the 89″ interior width of the bus.


I had considered spraying in foam insulation but with the bus already having the ceiling done, pre-built cabinets and kitchen pieces in place it would be more work and mess and more expensive than replacing insulation in the walls with additional foam sheets.  We started by replacing any old insulation that was not holding up and filled any other holes in the insulation with great stuff spray foam.  This gave us a nice tight seal between the outside aluminum panels and the inside of the bus.  Before I get into the layers of insulation lets talk about the funny math.

Spraying insulating foam between the cracks of the old insulation



After deciding to add an additional 3/4″ of insulation to the walls, I had to figure out how to lay out the nailers (furring strips) for the new walls. This is where the funny math came into play.  The vertical frames on the the bus are spaced at about 54″ on center.  The horizontal frame is set off by about 30″ on center.  90% of building materials available are measurements based on a 48″ x 96″ piece of plywood typical for wood framed houses built with 16″ frames on center.  I had to figure the best way to put up enough nailers to hold the wood and also cut the wood in such a way that I wouldn’t have to buy (20) 4×8 sheets of wood to cover each 54″ x 60″ frame in the bus.

Not lining up – Click the picture to see the dimensions

The best solution I could come up with was to set full length (60″) nailers at 18″ apart.  That would give me enough steel to firmly mount the furring strips to the frame (top, center and bottom) and get me 3 nailers between each 54″ vertical steel post.  I could also put extra screws into the steel bracings at the bottom of the frame.  I used 1.5″ self tapping stainless screws to mount the furring strips right to the frame of the bus.

All framed and insulated. Ready for the walls to go up.

Cutting the wood was a little tricky.  By cutting the plywood into a 90″ x 30″ strip it would leave me with leftover strips at 90 x 18″.  This way I could cover 5 of the nailers across on the top and bottom and cut 18″ x 30″ pieces from the 18″ wide leftovers to fill the individual gaps where needed.  This worked out nicely.  It left a few gaps to be filled and sanded but the cost of wood and headaches was kept to a minimum.

Here you can see where an 18″ x 30″ piece is needed to fill a gap.

Back to the insulation – It seems there are many layers in our bus.  Here is a brief layout of each layer –

1. Outer Skin – Thin layer of aluminum covering the outside of the bus frame.
2. 1.5″ Foil covered foam insulation.  Gives a good thick layer of insulation between the frame of the bus.
3. 1/8″ Reflectix insulation.  This covers the frame on the inside of the bus and prevents heat from transferring through the frame into the walls of the bus

4. 3/4″ R4.0 Blue foam board insulation.  This adds an additional layer of insulation and keeps the cool AC inside the bus from escaping.
5. Walls – Inside layer of 1/2″ wood to finish off the inside of the bus.

And a video to better explain our “Wall Sandwich”

Soon to come – More Walls and Flooring!


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