Bricks. - In considering the essential qualities of bricks for the small house it must be appreciated that those bricks which are used on the exterior must be able to resist the effects of weather and produce the best artistic results, while those which are in the interior of walls or chimney need not be held up to such rigid standards. The determination of the resistance of bricks to frost and weather action is quite simple. A brick which struck by a hammer gives a clear ring is one which has been well burned and has no soft spots, cracks, or weak places. Such a brick can be said to be satisfactory for exterior use, provided that it has the proper form and color desired and is not so overburned as to be twisted and warped. Another requirement sometimes specified is that the face brick made from soft clay should not show a percentage of absorption in excess of 15 per cent, and for the stiff-moulded or dry-pressed bricks not more than 10 per cent. This, however, cannot be a hard-and-fast rule, due to the variation of clays-Certain red bricks, unless they are burned very hard, show, when built into the wall, a very ugly white surface discoloration, called "whitewash" or efflorescence. This is not entirely due to the brick, since the mortar that is used may sometimes produce it. If it is due to the brick it can be discovered before the brick is used in the wall, by placing a sample brick on edge in a pan containing one inch of either rain or distilled water. As the water is absorbed by the brick, the white discoloration will develop on the top surface after several days of standing if it contains the salts which will cause the whitewash. Those bricks which have been very hard-burned will not discolor under any circumstances. If after passing this test the brick wall should develop whitewash, it can be laid to the mortar. In order to prevent any such occurrence it is necessary to waterproof the joints around window-sills and between the foundations and the wall, so that the minimum amount of water will be soaked up into the wall when it rains. An expensive addition of 2 per cent of barium carbonate to the mortar will tend to fix the soluble salts which cause this efflorescence.
Hollow Tiles. - Hollow terra-cotta tiles covered with stucco or brick veneer are being used more extensively than ever, due to the cheaper cost of laying them, since they are larger units, and also to the fact that they build a cellular wall. Wherever these tiles are used for bearing walls it is important that they be hard-burned, but the softer ones may be permitted in non-bearing partitions. Tiles for use in outer walls should be hard-burned, free from cracks, straight, and should not show a greater absorption of water than 10 per cent. As these tiles are intended to support loads from floor-joists, it is essential that they should have the correct proportion of voids to solid shells and webs. The maximum width of any voids should not exceed 4 inches and the thickness of any shells or webs should not be less than 15 per cent of this measurement. In tests it has been shown that tiles laid with webs vertical are stronger than those with webs horizontal, but this difference in strength is not of very great importance in the small house, where the loads are very light. The chief thing to avoid in the setting of tile, when they are vertical webbed, is the dripping of mortar to the bottom and the insufficient spreading of it over the ends of the webs and shells. This can be overcome by laying wire lath over each course, and then buttering the mortar on the inside and outside edges. The mortar is prevented from falling out of place by the lath, and because it is not continuous through the wall, any penetration of moisture through it is stopped.
Method of testing a sample brick to see whether it will have a tendency to whitewash.
Showing the use of metal lath in the joints of vertically webbed hollow tile, to prevent the dropping of the mortar into the voids and also allow the separation of mortar joint.