The compressive strength of the individual tile depends upon the materials used and upon the method of manufacture, in addition to the thickness of the shells and webs. A minimum compressive strength of tile masonry of 300 lb per square in, based on the gross section may be expected. The tensile strength of structural clay tile masonry is small. In most cases, it is less than 10 percent of the compressive strength.

The abrasion resistance of clay tile depends primarily upon its compressive strength. The stronger the tile, the greater its resistance to wear-ing. The abrasion resistance decreases as the amount of water absorbed increases. Structural clay facing tile has excellent resistance to weathering. Freezing and thawing action produces almost no deterioration. Tile that will absorb no more than 16 percent of its weight of water have never given unsatisfactory perform-ance in resisting the effect of freezing and thawing action. Only portland cement-lime mortar or mortar prepared from masonry cement should be used if the masonry is exposed to the weather.

Walls containing structural clay tile have better heat-insulating qualities than walls com-posed of solid units because of the dead air space that exists in tile walls. The resistance to sound penetration of this type of masonry compares favorably with the resistance of solid masonry walls, but it is somewhat less.

The fire resistance of tile walls is considerably less than the fire resistance of solid masonry walls. It can be improved by applying a coat of plaster to the surface of the wall. Partition walls of structural clay tile 6 in, thick will resist a fire for 1 hr provided the fire produces a temperature of not more than 1700F.

The solid material in structural clay tile weighs about 125 lb per cubic foot. Since the tile contains hollow cells of various sizes, the weight of the tile varies, depending upon the manu-facturer and type. A 6-in. tile wall weighs approximately 30 lb per square foot, while a 12-in. tile weighs approximately 45 lb per square foot.