Brick should be sound, free from cracks or flaws, stones, or lumps. They should be of uniform size, with sharp edges and angles, and true and square surfaces. If two good brick are struck together, they give out a ringing sound; while if the sound is dull, the brick is of inferior quality. A good brick will not absorb more than 10 per cent, of its weight of water; the best will not absorb over 5 per cent., while soft brick will take up from 25 to 35 per cent.

The crashing strength of good quality brick should not be less than 4,000 lb. per sq. in. Most good brick will have 2 or 3 times this strength. The weight of a common brick is about 4 1/2 lb., or 118 lb. per cu. ft.; pressed brick of the same size will weigh 5 lb. each, or 131 lb. per cu. ft.

The size of brick is variable, as shown by the following table. The standard brick, adopted by several associations of builders and makers, is 8 1/4" X 4" X 2 1/4" for common brick, and 8 3/8' X 4 1/8" X 2 1/4" for face brick.

Size Of Brick

Terra Cotta

All pieces of terra cotta for external work should be tested before use. They should emit a metallic sound when struck, and a fracture should show close texture and uniform color. The surface should be hard enough to resist a knife scratch, and the glazing should not be chipped off. Solid terra cotta weighs about 120 lb. per cu. ft., while hollow pieces of ordinary size average from 65 to 85 lb. The safe working strength of terra-cotta blocks in walls is about 5 tons per sq. ft., if unfilled, and 10 tons, if filled solid with concrete.