Originally Posted by taskswap
I figured I would use thick plywood screwed to the vertical struts as a mold and plastic sheeting as a release - the pour foam I've used in the past was pretty happy letting go of that. It's just a pain to do overhead, so I guess I've been still poking around looking for an "elegant" solution.
It pains me to see all you guys adding all this plywood and OSB to the floors, walls, and roof of the buses.
If you strap the walls, you can glue 1.5 to 2 inch thick sheets of rigid Styrofoam right to the strapping. This is far lighter, and just as strong as plywood. Your finish wall covering glues right to the inside of the rigid Styrofoam. Finish wall coverings can be FRP, arborite, paneling, ect. Cupboards, and things mount with screws through the rigid Styrofoam into the strapping.
This cuts the weight, the thermal mass, and creates a perfect thermal break, uses half as much spray or pour foam, saves money on plywood, eliminates all that extra wood in the walls and ceiling.
Floors are even easier.
Everyone thinks you need a mechanical fasteners to hold something in place, not the case. We live in a world of adhesives.
Again, there is no need for furring strips, strapping, or any wood what so ever in a floor. There are builds on here where people think they need to support the plywood in the floor with 2x4's, suspending the plywood / OSB over the rigid Styrofoam, leaving a air gap. Its like people think the rigid Styrofoam can't take the weight.
Well it can.
Concrete here in Canada all gets rigid Styrofoam under it to insulate it from the earth, and stop the damaging frost. The blue rigid Styrofoam comes here in two grades. 2000 and 3000. That number references to how many PSI the Styrofoam can take per square foot.
Long story short, the flooring in our buses will never see the weight that a concrete floor does. Therefore no wood is need to support the subfloor in a bus.
Now for floor sheeting, or "subfloor", the layer that your finish flooring secures to.
Most fellow members use OSB, or plywood simply because they have seen it done, and cost. But your putting wood back in a floor to rot, mold, get bugs in it, ect.
16 and 14 galvanized steel makes a great subfloor layer. Again using adhesives, it simply glues to the rigid Styrofoam sheet below it. No mechanical fastener is needed. Finish flooring glues right to the top side of the galvanized steel. Flooring like vinyl plank, VCT tiles, ect work really well.
So starting from the old steel floor of the bus, glue one or two layers of 1.5 or 2 inch rigid Styrofoam to the steel floor, then glue the next layer to the first. Now cut in your in floor heating lines, glue your galvanized metal subfloor to the surface of your Styrofoam with your new heat lines, and glue your finish flooring onto the surface of the galvanized metal. Done
You now have a far stronger, lighter, rot proof, bug proof, warm floor that would stay in place even if you rolled the bus.
Just install the plywood or what ever your sheeting the walls with, then pour the foam. The foam will bond to the back of your sheeting, and save you a few steps. No need for the plastic, or to remove anything.