Chimneys Roofs

ROOFS, CHIMNEYS, ETC.

Concrete Roofs. It

will be impossible to build a concrete roof that will not crack, unless the walls are rightly constructed and on a foundation that will not settle. Roofs require special care to render them water-tight. The sinking of the brickwork on new structures is often the cause of cracks in a concrete roof. Of course a crack in a roof of this material is more serious than in any other work, as it means a leaky building. The rough coat should be laid and solidly rammed and compressed. So far as possible, the top coat should be laid in one piece. Roofs exposed to the sun should be kept damp for a number of days after being laid, as they are easily affected by the heat. Expansion may be counteracted by the use of strips around the walls. A skirting six inches high and one inch thick should be keyed to the walls. A good top coating is made with one part Portland cement, one-half part of slaked lime, and one part of fire brick dust.

Cement shingles of various shapes and de signs—in some cases reinforced with fine wire mesh—are beginning to be used extensively, and are giving the best of satisfaction when properly laid. They are applied in the same way as slate, and provision must be carefully made to avoid cracking during the process of laying. In some instances this is done by inserting in the body of the shingle small pieces of asbestos board through which the nails or screws may be driven.

Cement Brick for Chimneys.

Concrete blocks and cement brick make desirable chim neys; and, if care is used in the construction, entire satisfaction ought to be attained. Dry concrete being fireproof to the extent of its raw material, it has been found that sand usually en dures more heat than cement. It is therefore necessary to select a cement that has been highly burned—no less than 1,200 degrees—which will make a chimney safe. But the chimney may dis color at 800 degrees without injury. For wood and soft coal fires, Portland cement is acceptable. For hard coal and coke, the cement must be selected, and gravel, limestone, and soft sand stone must be omitted. The inside of the chim ney should be plastered with mortar made of one part cement to three parts of sand, mixed with strong salt water.

Cement Roofing.

The practicability of ce ment roofing is no longer a question. It was in troduced in the United States several years ago, and its use spread very rapidly, so that we now find its application in many States, on nearly every class of building. There are a number of concerns manufacturing concrete roofings of one type or another, nearly all of which turn out a product which is giving universal satisfaction.

The question of obtaining satisfactory roof ing for industrial plants has been a perplexing problem for some time. There are a number of roof coverings which give satisfactory service for a time; but, when subjected to the elements, it is only a matter of a short period until they are partially or totally destroyed. The fumes and gases from furnaces and factories, prevalent in manufacturing districts, attack the old-time roofing, and accomplish the work of destruction in a comparatively short time. The natural ele ments bring the same results in a somewhat longer period.

Cement roofing has proven itself economical, practical, and durable. While the original cost of this kind of roofing is somewhat more than that of slate or other materials, in the end the concrete covering always proves the most econ omical.

Cement roofing tile have proven their tability on a large number of buildings of prominent industrial concerns. The tile are re inforced. The weight, which will about equal that of a slate roof on two-inch sheathing, is in the neighborhood of thirteen pounds to the square foot. The tile are about seven-eighths of an inch in thickness, cover a space four feet long by two feet wide, and are attached directly to the purlins. A permanent red color is ob tained in these tile, which is claimed to be non effaceable by the elements, requiring no painting. The tile are self-adjustable and interlocking, which provides in every way for expansion, con traction, and vibration, and at the same time afford a covering unaffected by temperature changes, and one which is fireproof and water proof. See Plate 1, upper figure.