Can i skip the plywood in the subfloor?

[tj-grant]

If i can get a hold of this (looks like 1”) shiplap cedar. Could i just glue it down onto the xps foam board I’m using to insulate the floor? Instead of using plywood and hardwood floor can i just fasten this stuff on top of the foam and be done? How should i fasten it? Chuck cassidy just glues his fancy osb. What do you think?

 

[Bjorkinman]

I would think you could do that. Just be sure to let the wood acclimate by leaving it in the bus for at least a few days. I would do the whole floor wall to wall and front to back then build walls and cabinets right over it. Just leave a 1/4 gap all the way around the perimeter for expansion.
Will be a sweet looking floor.

 

[Mr P]

Experiment with gluing to XPS. I've not found anything very good.

What movement (direction) do you want the glue to eliminate?

What amount of force do you think the glue (or insulation material) will survive before the glue bond breaks to the panel shears?

 

[tj-grant]

I would think you could do that. Just be sure to let the wood acclimate by leaving it in the bus for at least a few days. I would do the whole floor wall to wall and front to back then build walls and cabinets right over it. Just leave a 1/4 gap all the way around the perimeter for expansion.
Will be a sweet looking floor.

Awesome. Do you think glue will hold or should i screw it’s down somehow?

 

[tj-grant]

Experiment with gluing to XPS. I've not found anything very good.

What movement (direction) do you want the glue to eliminate?

What amount of force do you think the glue (or insulation material) will survive before the glue bond breaks to the panel shears?

I am hoping that the glue will just hold it down. I want to avoid any squeaking and rubbing on the xps. I’m considering screwing some wood to the bottom walls to essentially create a slot for them.

 

[Ozbozz57]

Individual boards such as what you're considering will shrink and expand, warp, twist, bend, and split MUCH more than plywood or OSB. If they are the only layer bonded to your foam board, that bond will be compromised, possibly severely so. That would make whatever is attached to it compromised as well. I suggest gluing a layer of subfloor to your foam board and THEN adding the cedar shiplap, screwed down well.

 

[tj-grant]

Individual boards such as what you're considering will shrink and expand, warp, twist, bend, and split MUCH more than plywood or OSB. If they are the only layer bonded to your foam board, that bond will be compromised, possibly severely so. That would make whatever is attached to it compromised as well. I suggest gluing a layer of subfloor to your foam board and THEN adding the cedar shiplap, screwed down well.

Thanks! How thick should the plywood be?

 

[Ozbozz57]

Thanks! How thick should the plywood be?

I'd use 3/4 inch. You might get away with 1/2 since you'll be covering it. I just sanded, stained and polyurethaned the 3/4 plywood on my floor. You might consider the same, maybe use the cedar on the walls?

 

[#1FordFan]

The best bet for a stable floor is what’s in my house. Avantek Flooring it has a 50 year warranty and uses water proof glue. Not much more expensive than std plywood

 

[LargeMarge-TC]

... shiplap cedar. Could i just glue it down onto the xps foam board I’m using to insulate the floor? Instead of using plywood and hardwood floor...

.
1)
As the planks shift with road-vibration, I wonder if they will 'lift-n-separate' the glued sections of the foam-board from the main body of your foam-board?
.
2)
In our ExpeditionVehicle, we painted marine plywood on all surfaces to seal, then laid it atop our one-inch pinkboard insulation.
This bridges potential gaps between sections of pinkboard.
.
Our visual floor is bamboo perimeter with slate in the center.
Over two decades full-time live-aboard, pretty much zero upkeep.
.
3)
Your Cedar planks probably need sanding and sealing?
How resistant is Cedar to gouging by high-heels and dropped skillets?

 

[nikitis]

You can use PL300 to glue it down, but I'd recommend planing it first to smooth it out so you don't get splinters, and then seal the top layer with polyurethane.

The polyurethane if laid on thick will also help hold it all together as it seals the cracks into one piece. If you have cabinets holding it all in with the PL300, it'll work out just fine.

You could also buy a cheap underlayment from Lowes. $30 a roll, probably only need 1, maybe 2 rolls max and it'll make the walking a tad nicer.

 

[tj-grant]

I'd use 3/4 inch. You might get away with 1/2 since you'll be covering it. I just sanded, stained and polyurethaned the 3/4 plywood on my floor. You might consider the same, maybe use the cedar on the walls?

So you didn’t add anything on top of the plywood? I’ll use the cedar elsewhere. It’s too soft to use for the flooring.

 

[tj-grant]

.
1)
As the planks shift with road-vibration, I wonder if they will 'lift-n-separate' the glued sections of the foam-board from the main body of your foam-board?
.
2)
In our ExpeditionVehicle, we painted marine plywood on all surfaces to seal, then laid it atop our one-inch pinkboard insulation.
This bridges potential gaps between sections of pinkboard.
.
Our visual floor is bamboo perimeter with slate in the center.
Over two decades full-time live-aboard, pretty much zero upkeep.
.
3)
Your Cedar planks probably need sanding and sealing?
How resistant is Cedar to gouging by high-heels and dropped skillets?

So your flooring is just the painted plywood atop the foam board, no finish wood (hardwood floor)?
We’ve reconsidered the cedar flooring it’s way too soft to use for flooring.

 

[LargeMarge-TC]

...your flooring is just the painted plywood atop the foam board, no finish wood (hardwood floor)?...

.
Our visual floor is bamboo t&g* plank perimeter with slate in the center.
.
Everything lays atop the painted marine plywood, held in-place by gravity and hope.
Components with chips and dents can be quickly removed and replaced.
Fact is, we occasionally re-arrange the floor just for a different look.
.
Fact is, at the local-owned family-operated lumber-yard, we enjoy sorting through their slate for interesting patterns and colors.
Who knew floors could be so fun.
.

.
footnotes:
* t&g refers to 'Tongue and Groove', a way to stabilize the planks.
.
An aside:
Over two decades full-time live-aboard, this particular one-inch pinkboard shows zero compression or crumbling.
I am impressed.