Q. Can I use a pneumatic nail gun to fasten tile backerboard to floors and walls?

A.Michael Byrne responds: ANSI (American National Standards Institute) specifications require that a corrosion-resistant roofing nail be used when nailing tile backerboard, and that the nail penetrate the wood framing at least.

3/4 inch. While there are no direct references to pneumatic nailing, I see no reason why pneumatic roofing nails couldn’t be used, as long as the fasteners were of sufficient length. It’s important that the nail head does not break the fiberglass matting material imbedded in the backerboard, so make sure to properly set both the gun’s depth adjustment and the air pressure.

Corrosion-resistant screws can also be used, providing their head diameter is large enough to resist a 125-pound pull-through force. Hi-Lo S Rock-On screws (ITW Buildex, 1349 W. Bryn Mawr Ave., Itasca, IL 60143; 800/323-0720) meet this requirement.

Backerboard installed over a plywood subfloor should always be fully bedded in mortar or adhesive. In these situations, many contractors mistakenly think that the fasteners serve as clamps and that their holding power is not an issue after the mortar or adhesive "grabs." But the primary function of the setting bed is to provide a leveling bed for the backerboard; the fasteners are what holds the backerboard in place for the life of the tile installation.

For detailed guidelines on tile installation requirements, contact the Tile Council of America (P.O. Box 1787, Clemson, SC 29631; 864/646-8453) for a copy of the Handbook for Ceramic Tile Installation.

A tile contractor for more than 20 years, Michael Byrne is now director of the Ceramic Tile Education Foundation in Clemson, S.C.