Styrofoam insulation rules

[bintyre]

I know that 1/2 drywall is required to cover styrofoam insulation used on the interior walls, but I'm wondering if 1/2 cement board would be okay in areas where tile is to be installed. Thanks.

[concretemasonry]

I would think it would be adequate, but that is only an opinion. The codes will tell you if it is acceptable.

[ITE]

You should ask your code offical to be positive, however, I don't think you will have a problem with that. The thing you have to be concerned with is how good of a thermal barrier the material is. That is part of the purpose of the drywall, to act as a thermal barrier. I would like to add that if you are installing tile someplace where it will get wet a lot you will probubly want to use something besides drywall as the backing. The tile will let water through, getting the wall wet and resulting in the tile falling off eventually.

[David]

I would like to add that if you are installing tile someplace where it will get wet a lot you will probubly want to use something besides drywall as the backing.

He's gonna use cement board under the tile.

[MCC]

Cement Board Has A Higher Firerating Than 1/2 Gypsum Board As Lond As You Still Tape The Joints Properly So There Shold Be No Reason Not To Use It.

[Don_P]

My acrobat reader just burped, you should be able to find it in here;
Durock, http://www.icc-es.org/reports/pdf_files/NES/NER-259.pdf
Perma-Base, http://www.icc-es.org/reports/pdf_files/NES/NER578.pdf

Never seen the second product in the field, we have Durock here.

Builders keep this adress to look up the code required ES reports if your inspector ever needs one;
http://www.icc-es.org/Evaluation_Reports/index.shtml

[MCC]

Nice Site To Bookmark. Thanks

[Sweep]

Foam plastic insulation must be separated from the inside of a house by a min. of 1/2" regular GWB or an approved finish material equivalent to a "thermal barrier" to limit the average temperature rise of the unexposed surface to no more than 250°F after 15 min. of fire exposure to the ASTM E119 standard time temperature curve. It has to be installed with mechanical fasteners but I have never seen a requirement for taping of joints.

This is not a "fire-resistance rated assembly" intended to prevent the spread of fire; it is a "protective thermal barrier" intended to keep the foam from releasing harmful gasses before occupants can exit the house.

GWB has good fire-resistance and thermal barrier properties because it releases water vapor when heated which cools the assembly as it vaporizes. It and other materials carry no fire-resistnce rating by themselves but can be rated as part of an assembly. (Type X GWB is defined as 5/8" GWB that will achieve a 1-hour fire-resistnace "rating" if installed on both sides of a wall stud, but that doesn't give Type X GWB a fire-resistance "rating" by itself.)

The thermal barrier over foam plastic insulation is not required when the foam is protected by 1" of masonry or concrete.

I would get the building inspector's approval before using a fiberglass reinforced concrete backerboard as a thermal barrier unless you can find evidence of its thermal barrier properties listed in an ICC ES report.