XPS in basement and framing

I want to put XPS on my cement floor and walls. I was going to level the floor first, then put the XPS on, OSB subfloor over that, then the framing. Is this the best way to go?

Also, I was going to chisel down an unusually high corner of the basement floor before using thinset to level out the low spots. It seems like this is an acceptable solution, but wanted to make sure.

Thanks!

 

Welcome to the forums!!XPS on the floor will create a spongy feeling in the OSB. What will your final flooring be? If you plan on doing this, you should frame the walls first, then lay the subflooring (which I do not advocate...others may find it fine and will chime in here). If you have an area that needs grinding, you can do it, but you should use a self leveling floating compound rather than thinset to fill in low spots.

Larry

"Half of communications is listening, and you can't listen with your mouth"

 

I saw an article in Fine Homebuilding a while back on basement floor insulation. It recommended roughly what you suggest. Frame up the floor with PT laid flat, 16"OC, shim as need to level, then 3/4 OSB. Fill the gaps tightly with XPS. Same suggestion for walls, more or less. Regular fiberglass insulation for an exterior basement wall is a BAD idea.

Forget the chipping and leveling cement, way too much work with poor results.

 

Now I can possibly see that, because it has support. Plywood over raw XPS panels I don't think would be advisable. So, Bill, you are saying build sleepers first, then fill voids with XPS?

Larry

"Half of communications is listening, and you can't listen with your mouth."

 

I am planning on putting down laminate flooring, so I really need a nice level floor.

If I frame first, then don't I leave myself at risk for moisture (bottom plate right on the basement floor)?

Also, I don't see how I can just abandon trying to level the floor. In one corner, for example, it is about 1 3/4 " above the lowest point in the middle of the floor.

 

Bottom plate should go on a foam sill gasket (normally used for sill plates above block walls). You can also use pressure treated wood. Using one or both of these it should be ok on the concrete with that wood. The gasket alone will be a capillary break so moisture in the concrete cannot wick into the bottom plate.

I have never been on an XPS+ply floor but Mike Holmes and people on his forums regularly use this approach. I think they use 3/4" OSB, for what it's worth. I read about all these and decided in my case I'd not be putting down a subfloor in my basement.

PT sleepers filled with XPS and sheathed in ply or OSB could work but goodness it sounds like a bit of work. One reason I don't want a subfloor in my basement is that despite it being dry and a walk out, if I ever do get flooding the subfloor is just more potential damage. But without it, water would at its worst just require a replacement of the flooring (e.g. carpet) and not subfloor. I've never heard from anybody who had a lot of water with one of these subfloor approaches but I could see it sitting between the XPS and wood for a long time. There is also the height issue.

From an insulation perspective not much heat is going to be lost through a basement floor anyway. The earth below that slab is cool but not cold and although insulating from it would help in the winter, in the summer you don't get its cooling effect.

A huge hump like you describe sounds hard to deal with. I'd almost think about just cutting that portion of the floor totally out and putting in new concrete. You cannot grind down 1+ inches and chiseling it would be a chore.

If you had access, however, to a diamond blade saw perhaps you could cut a vast number of score marks the depth you want and then use a chisel to come in from the side and chip these little rectangles/squares out?

 

Chandler.....I am not saying that, the article did, but it made sense to me. I will see if I can find it. I also think there was a vapor barrier under everything..........or was it over the framing, under the OSB??????? No, under everything.

 

I kind of thing I have seen this in one of my basement books. I question the point of the vapor barrier over concrete that has it directly underneath it, though; seems to be redundant.

 

The plywood or OSB on top of the XPS panels is something I did see on the Mike Holmes program, which is where I got the idea. By XPS, I mean the 8 foot sheets of foam board. If I misspoke or used the wrong term, that's my mistake. So I was going to glue these sheets to the floor and the walls, use weathermate tape (or something similar) on the joints, and where the corners meet, use spray foam. Oh and leave 1/4" expansion around the floor between the panels and the walls and fill that with spray foam.

BTW: Here is a link to that segment on Youtube: YouTube - Best way to insulate a basement 800x600

I like the idea of making a lot of cuts in the high corner, then chiseling it out. Sure it's a lot of work, but I can't lose that extra inch of ceiling height by leveling the whole floor to that high spot (if that makes sense).

In either case, I was planning on using a PT bottom plate, and at least 5/8" OSB as a subfloor (either alone or over the foam board). But I think I have to put some sort of subfloor down first since I was planning on using laminate flooring, isn't that correct?


When you guys refer to "filling with XPS", do you mean cutting up the board and placing it tightly in between the gaps (the 16" between the PT boards)?

Thanks again for your advice.

 

What about INSOFAST paneling, check it out at insofast.com? It's also eligible for the tax rebate. I'm not affiliated with the company in any way. I was looking into this product last year and they said no problem for use on a floor. I think it can like like 900 lbs/sqft or something. This would give you some added structural support with the impregnated plastic pieces and the insulation you need. Anyone had any experience with this product? Sorry to jack the thread.

 

I haven't seen it for that although maybe it could be used for it. BTW, the XPS from lowes/home depot, is rated for compressive strength. For example, the Owens Corning Insular 250 is at 25 lbs per square inch or something like that--more info on their site. That seems extremely high, though based upon my use of it; 3600 lbs would smush it down into no man's land, so maybe I'm off by a decimal or two

 

We decided against a subfloor, and will be using an epoxy floor instead of laminate. I just need to research about resolving issues when framing on uneven floors with cement walls that are out of plumb.