Subflooring Insulation: XPS vs Polyiso

[Stu & Filo. T]

Memphis: I agree with what Flyboy says. My plywood(2nd choice osb) will be 1/2, or 9/16 (whatever is cheap and close to that thickness at home depot/lowes).

IMHOP, what I've read about OSB is it should not be used on a floor because when produced it is sealed & if you cut it & don't reseal it the moment moister hits it it starts disintegrating.

 

[TAOLIK]

IMHOP, what I've read about OSB is it should not be used on a floor because when produced it is sealed & if you cut it & don't reseal it the moment moister hits it it starts disintegrating.

+2 points for plywood, that's all the reason I need to stay away from osb.

 

[Tango-SKO]

Ya...OSB will swell up like a sponge if it gets moist. I'm going with marine ply.

 

[youngrider]

Scratch that, I just found a vendor who carries 1/2" xps insulation at $20ish with no minimum! Life is good! Ooooooh my goodness, these little victories sure feel good.

Taolik, this is a long shot,but here it goes: I have been struggling to find XPS 1/2" thick in the Seattle area. Even drove to a place in Kent that stated over the phone that they'd sell me less than five 4' x 8' sheets, they lied!! Everywhere I look it seems that it is not less than 1" thick or they don't sell to the general public.

Can you share what place in Kent you found that sold you small quantities of XPS back in 2016??

 

[TAOLIK]

Oh man, I'm so sorry to hear about that. I was pretty frustrated and definitely had similar experiences in my search for 1/2" xps. I just checked my online banking and wasn't able to find any of my transactions but I'll call them on Monday and see if they can pull anything up.. I really wish I remember where I got it from, I think it was kent or maybe tukwilla, and I think I was referred there from a different business. Well I'll take a look on Monday.

Taolik, this is a long shot,but here it goes: I have been struggling to find XPS 1/2" thick in the Seattle area. Even drove to a place in Kent that stated over the phone that they'd sell me less than five 4' x 8' sheets, they lied!! Everywhere I look it seems that it is not less than 1" thick or they don't sell to the general public.

Can you share what place in Kent you found that sold you small quantities of XPS back in 2016??

 

[Biscuitsjam]

I used 1 inch poly iso on the floor and 1/2 inch plywood floor.

My observations:

1. The poly iso compresses... a lot... I had to do a ton of work to keep the floor from squeaking and shifting under me. XPS is much better for floor insulation because it doesn't compress much.

2. I'm also 6'3". However, I wish I had done the 1.5" XPS. At 10 degrees outside and 55 inside, I spilled a drink. It froze on the floor.

3. I bought a bus that somebody had started converting and then quit almost immediately. He used OSB for the floor, and it was a mess. When I ripped it out, a lot of of it was swollen and warped. Much of the bottom side was also covered in black mold.

4.The previous owner had not removed or treated the rust on the metal subfloor and had instead just covered over it with rustoleum paint. The rust started bubbling up under the paint and would have turned into a disaster. However, none of the paint stripper chemicals would remove the rustoleum. I ended up grinding it off over 40 hours of labor. Ugh.

5. I used luxury vinyl tile flooring (fake hardwood) and then built the furniture over it. I've had a lot of gaps open up. I recommend not doing a "floating floor" and instead securing it to the floor. I haven't fixed it yet, but it irritates me every time I look.

Good luck with your build.

 

[musigenesis]

I used 1 inch poly iso on the floor and 1/2 inch plywood floor.

My observations:

1. The poly iso compresses... a lot... I had to do a ton of work to keep the floor from squeaking and shifting under me. XPS is much better for floor insulation because it doesn't compress much.

2. I'm also 6'3". However, I wish I had done the 1.5" XPS. At 10 degrees outside and 55 inside, I spilled a drink. It froze on the floor.

3. I bought a bus that somebody had started converting and then quit almost immediately. He used OSB for the floor, and it was a mess. When I ripped it out, a lot of of it was swollen and warped. Much of the bottom side was also covered in black mold.

4.The previous owner had not removed or treated the rust on the metal subfloor and had instead just covered over it with rustoleum paint. The rust started bubbling up under the paint and would have turned into a disaster. However, none of the paint stripper chemicals would remove the rustoleum. I ended up grinding it off over 40 hours of labor. Ugh.

5. I used luxury vinyl tile flooring (fake hardwood) and then built the furniture over it. I've had a lot of gaps open up. I recommend not doing a "floating floor" and instead securing it to the floor. I haven't fixed it yet, but it irritates me every time I look.

Good luck with your build.

There's a young couple that posts their bus stuff on reddit. They built a floating floor out of just polyiso and OSB, and it was painful to see. I don't think there's a worse flooring choice than that.