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Q.I’m building an outdoor patio, and the plans call for a ceramic tile counter near the grill. What types of vitreous tile are suitable for outdoor use?

A.Tile consultant Michael Byrne responds: The most important factor to consider when choosing a tile for outdoor use is how often the tile will freeze, which depends upon the climate. In southern California or Florida, where an exterior tile installation might only freeze once in its lifetime, almost any tile will do. In a climate that has a frost once or twice a year, a vitreous tile should be fine. If your area gets a frost more than once or twice yearly, however, you need to use an impervious tile. Impervious tiles do not absorb any appreciable moisture that might expand when the tile freezes. Using substandard materials or methods can result in the loss of the tile after only one freeze/thaw cycle.

The tiles should be installed with latex-content thinset mortar and premium-quality latex grout. I recommend installing a sloping subsurface, a drainage layer to allow for runoff, and a crack isolation membrane to absorb differential movement between the tiles and the setting bed.

The correct placement of expansion joints is essential to the performance of the drainage and crack isolation membranes. Without them, an otherwise solid installation will eventually fail. On most tile installations, an expansion joint filled with caulk (instead of grout) is required wherever tiles change direction or meet other materials. In the case of your counter, you will need an expansion joint of at least 1/8 inch between the grill and the tiles. Since high heat may cause toxic fumes to be emitted from the caulk, this joint slot should not be filled. Your grill’s housing may overhang the tiles, hiding the open joint. If not, make certain the tile installer keeps the joint slot open, with tile edges neatly aligned. Resist the urge to butt the tiles right up against the grill. If you leave no room for expansion, when the grill heats up and expands, it could shear the tiles right off the surface.