INSULATING UNDER TILE FLOOR OVER CRAWL SPACE


QUESTION FROM STACY, OKLAHOMA CITY, OK:


I hope you can help me out a little. My house has a crawl space....we cannot insulate underneath the part of the house that I'm writing about....there is a type of laminate down....most likely without backer board under it...I'm wanting to tile the floor...is there a type of insulation board that I can put directly on sub floor, and still install tile??? Thank you

 

ANSWER FROM THE INSULATION DOCTOR:

Hello Stacy,
 
I am not aware of any type of insulation that you can install and tile directly over it.  However, a couple options would be:
 
You can install a closed-cell Styrofoam product glued to the floor -- made by Dow (blue) or Owens Corning (pink) and then put a 3/8" plywood covering over the Styrofoam.   You must be sure to use a type of glue on the Styrofoam that will not eat the Styrofoam itself -- it has to be compatible.  The downside of this method would be that you have increased the height of the floor, therefore, you would have a lip at the threshold to any other room.
 
The second option would be to install a 1/2" cement board on the floor prior to installing the tile.  The cement board would have a minimal insulation effect, but would have more than a normal wood subflooring.  Cement board is not normally used on the floor due to the cost.  A 4'x5' sheet normally runs about $10 in Home Depot or Lowes.
 
Also be aware that if this happens to be a bathroom or a room with a drain (such as a toilet), you will need to raise the drain by putting an extension on it so you can make the connection. 
 
Those are the only suggestions I have for you and hope it helps.
 
Bruce Jones
The Insulation Doctor