Insulating floor

[Zizzer_Zazzer_Zuz]

I have a shorty bus, Ford E450, 22 feet... I think. 14 feet from behind the driver and 13 feet from the door well. Bus is 7.5 feet wide.

I will NOT be taking up all of the rubber floor and the rails that are used to anchor the benches. I will be using two benches for a dinnette and they must have something solid to attach to. This will give me legal passenger space for 4 adults. I will remove some of the hardware but not much more than flashing.

I have 3 10x4 foot sheets of 3/4 inch polyiso. I can trim 6 inches off of the long side of one panel and can lay them side by side lengthwise along the bus. The last panel will be turned 90 degrees to finish of the last 4x7.5 feet of flooring.

1) which would you put up front? The sideways panel or the two side by side?

2) How would you attach/affix/glue the polyiso to the floor?

3) Foil side down?

I am planning on simply laying 4x7.5 foot pieces of plywood on top of the polyiso. My basic intention, if at all feasible is to sand, stain and clear coat/polyurethane and be done. I'm good with rugs and being able to sweep with a broom and mop.

1) How do you keep the seams from coming apart? There will be three seams that will be under foot. How do you keep the panels from shifting?

2) I hear lots of people talk about leaving room for expansion along the walls. How much? How important is this really?

3) Odd sized piece along the front step or at the rear under the bed? Bed will be along back wall of bus.

4) How do you affix the plywood to the polyiso? Do you? 

Any thoughts or suggestions would be much appreciated.

 

[Every Road Leads Home]

I'd cut a groove in the plywood about 3/4" inch deep x 1/4" wide and insert a spline.  Not sure if that's something you have the tools for to do it.  Essentially it's creating a tongue and groove joint so there's no deflection when you walk across the seam.

Or you could use pocket holes and place them in spots that will be covered by furniture or plug them afterwards.  This will suck the plywood together as well, so no dirt can get down there and so it doesn't deflect when walking over it.  Probably easier to do it this way.  In the pic you can see a pocket hole and then a pocket hole that's been plugged.  You can buy a package of the plugs for $5 bucks at Lowes and Home Depot and the pocket hole jig is about $50.  And then use it for other parts of your build as well.

 

[DannyB1954]

Not real familiar with buses, but anything that you put on the floor needs to be supported on the edges, (foam or plywood). Some vehicles have something like a corrugated metal floor. The ends of both sheets have to be supported on one of the high sections. You can fill in a low section with a spacer if you need the ends to go there.

As far as expansion, that depends what you use for flooring. Different wood flooring needs different amounts. If you use something based on plywood you will need less than something made of solid wood. Vinyl or carpet don't care if you have any.

Fixing the plywood to the foam is usually done with screws that go through both and then through the floor. Just make sure nothing is going to get punctured where they go through, ( like a fuel tank or wire harness). A lot of foam's do not like glue. I wouldn't trust it alone.

 

[Zizzer_Zazzer_Zuz]

I'd cut a groove in the plywood...

Or you could use pocket holes a...

I did see subflooring that had a T&G along the long side. It was very rough and would be hard to finish. I want to limit thickness on the floor to preserve what little head room I have and I will be losing 2+ inches with the floor and the ceiling. 

I'm liking the pocket holes but may not have enough wood. I may just need to drill screws through the plywood and polyiso into the wood subfloor beneath.

 

[highdesertranger]

most recommend not to insulate the floor. after all if you want to preserve your head room. highdesertranger

 

[Reducto]

I don't think foil up or down makes a difference. That stuff is meant to face an air gap which you won't have.

I wouldn't glue the poly down or attach the plywood to it. Screw or bolt down the plywood through the insulation and it will all stay put.

The pocket screw jig is great to have around whether you use it for this or not. Tongue and groove would be ideal, but anything to keep one side from lifting would be good.

If you have a choice of where to put seams, put them underneath furniture or storage rather than where you want to stand.