We're pulling out the carpet in a room next to a room with hardwood floors. After removing the carpet and putting down the engineered floor, we'll be 1/4" short of the hardwood.


  • Use transition strips for the 1/4" difference

  • Put down 1/4 ply on top of the current subfloor

And then I thought of a 3rd option:

  • Put down 1/4" Extruded polystyrene (XPS) panels.

The XPS seems intriguing for a couple of reasons:

  • While not a lot of insulation, it wouldn't hurt
  • It may cut down on the 'hollow' sound that engineered floors sometimes produce
  • It'd do double duty and act as the underlayment (vs rosin or tar paper)

Thoughts on that? Is that a good idea? Any cons that I'm not thinking of?


Per Eric's suggestion, I finally called them and got a vague answer that was basically "you can put it on most anything that is flat provided it doesn't have any give". They felt the XPS might have too much give and stress the joints.

So, I suppose that is the question, how much give DOES XPS have? I've walked on XPS boards with shoes plenty of times (I'm over 200lbs) and didn't leave a mark, so itis a material that seems to have fairly decent compression resistance provided the load is spread a bit, and it seems that the flooring would certainly help spread the load more than my shoe would.

  • Isn't XPS too soft to be used directly under the finish floor? Seems like one jumping teenager could do a lot of damage to your floor. Commented Oct 22, 2012 at 1:49
  • I think there is a specific product available for floors
    – Steven
    Commented Oct 22, 2012 at 1:56
  • I guess that could be the case, but XPS, under the distributed load of flooring seems extremely sturdy.
    – DA01
    Commented Oct 22, 2012 at 4:12
  • Do they even make 1/4" XPS? What would be the point in it as it's an insulation material - R1.25 is barely any insulation
    – Steven
    Commented Oct 22, 2012 at 15:05
  • They do make it--at least I think do. I know I've used really thin XPS before (mainly as a thermal break between metal framing and concrete)
    – DA01
    Commented Oct 22, 2012 at 15:07

2 Answers 2


You can find the answer to your question in the installation instructions for the engineered floor that you are going to use, and if there isn't data there, call up the manufacturer and ask.

My guess is that it will not be allowed; the XPS is likely to deform easily, which leads that portion of the floor to be unsupported. Flexing of the floor at the seams is a bad thing.

  • No info in their instructions and no reply to my email yet, but you're probably right. Will attempt to call next.
    – DA01
    Commented Oct 23, 2012 at 2:42

I wouldn't use the xps if the hardwood is going to be nailed down then you can bet the nails will slowly begin to squeak when walked on because of the semi-soft xps. No manufacturer will give the go ahead on that, at least not without voiding your warranty. Go with a 1/4 in plywood and be done with it and worry free. On a side note wood is an excellent insulator. Solid log cabins have a higher R-Value than most homes.

  • It's an engineered floor (floating) so no nails. At this point, I'm looking at using 1/4" cork underlayment. Haven't gotten around to install yet but will report back when I'm done.
    – DA01
    Commented Feb 25, 2013 at 1:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.