Tech Tip: Ask NTCA Technical Trainer Robb Roderick
Q: Are there any standards or situations where it is acceptable to install ceramic tile over gypsum wall board and not a tile backerboard?
A: There are two methods in the Tile Council of North America handbook for installation of tile over gypsum board. Method W242 which employs organic adhesive for a setting material. And Method W243 which employs the use of thinset mortars that meet ANSI 118.1 or 118.4 or better.
In W242 (organic adhesive method) in the section preparation by other trades it states ” The maximum allowable variation in the tile substrate is 1/16 of an inch in 3′ with no abrupt irregularities greater than 1/32″. Both methods specify the gypsum board is to be installed according to GA216. ” Treated with tape and joint compound with bedding tape only( no finish coat) Nail heads, receive only one coat.
In Method W243 (thinset method) it states ” Maximum allowable variation in tile substrate for tile with edges shorter than 15″ the maximum allowable variations is 1/4″ in 10′ from required plane with no more than 1/16″ variations in 12″ when measured from the high point of the surface. For tiles with at least one edge 15″ in length, maximum allowable variation is 1/8″ in 10′ from the required plane, with no more than 1/16″ variation in 24″.
So there are many standards depending on the type of tile and adhesive you are using.