The best known and cheapest fireproof material for outer walls is some form of hollow building tile sufficiently heavy to withstand water shock from a high pressure fire hose. This building tile is made in blocks of varying thickness, but the National Board of Fire Underwriters allow a preferential insurance rate for walls formed twelve inches thick. Blocks of this thickness measure twelve inches by twelve inches by twelve inches, and come plain or scored on one or both sides for the application of stucco or plaster. If this form of block is used it will be better for the sake of appearance to stucco the outer surface of the building either with a cheap rough splatter-dash coat or a smooth troweled surface. Stucco may be rendered any color by the addition of coloring mixtures. The same deductions are made for stucco openings as for wall openings.

Textile

A finished-face tile known as "textile," that requires no stucco, is also made by standard firms in twelve inch by twelve inch by six inch sizes. This block, when laid with rodded or raised mortar joints, presents a much better appearance than brick and costs but a trifle more than the ordinary hollow tile scored for stucco. There is also a tapestry-finished block, made in another form, which may be used at about the same cost.

All of these vitrified clay products are of the same composition as ordinary brick, except that in the process of manufacture they are baked in an additional degree of heat to render them more fire resisting. Building tile is made somewhat larger than brick and has vertical hollow air chambers between its exterior surfaces. The size and lightness of hollow tile makes it easier to lay than brick, and its hollow cells form a dryer and warmer wall in winter and a cooler one in summer.

Whole Blocks Only

Hollow tile can be laid much quicker than brick and costs about half the price per square foot to lay. If care be taken to specify that only whole blocks be employed, with corner, jamb and lintel blocks where required, a good bricklayer can set 400 blocks or about 400 square feet of wall in a day. Ordinarily much time is lost in patching broken blocks where no such provision is made, and 200 blocks are considered a good day's work. If the blocks be ordered on such specifications the block dealer will charge only for whole blocks, making full deduction for blocks arriving on the premises broken.

Proving their fire-resisting qualities, whole rows of hollow tile building walls stood plumb and uninjured at the recent great Baltimore fire, while brick walls lay crumbled in ruins. So, too, like gaunt sentinels, stood scores of steel Lally columns, later knocked down by men presumably employed in the interest of steel manufacturers.

A Severe Test

Another striking test of the fire-resisting properties of hollow tile was supplied by former Fire Chief Edward Croker of New York City, a recognized authority on such matters. Mr. Croker erected a fireproof bungalow on Long Island, with hollow tile walls and hollow tile floors, and invited a select coterie of friends to participate in a housewarming. The guests were served with the customary cocktail in a sitting room adjacent to the dining room before being ushered into the latter room for dinner. Once in the dining room, the door between the rooms was closed, and the guests enjoyed undisturbed for over an hour the refreshments proffered. At the conclusion of dinner they were bidden by the host to return to the sitting room to partake of coffee.

Imagine their surprise upon opening the door of the sitting room to find in that room nothing but a mass of charred ruins. While the guests had been dining Mr.. Croker's servant, acting upon directions previously given, had gone to the sitting room, saturated its contents thoroughly with kerosene and ignited them. The fire had consumed the entire furnishings of the room and burned itself out while the people in the very next room remained entirely unaware of what had happened.

Hollow Tile As Curtain Walls

In a steel-framed building the exterior walls are usually merely substantial curtain walls carrying comparatively light loads. In smaller theatres where no steel framing is employed, these hollow tiles may be set with their hollow chambers vertical, one above the other, and at all bearing points grouted or filled with a strong mixture of liquid concrete through these vertical cells to form concrete pilasters. When the concrete has set, monolithic concrete columns extending from the foundation base and capable of supporting great loads are the result. The framework for the floors and balconies, or for any other structural object, may be inserted into and rest upon these concrete uprights.

Division And Partition Walls. Interior Walls

Division walls should be laid with ordinary scored six-inch hollow tile blocks of sufficient strength to withstand the ordinary water pressure from fire hose, and partition walls of six or four inch tile partition blocks, or even thinner blocks made from gypsum. Where long stretches of wall occur, gypsum blocks should be braced by occasional rods or angle irons extending from the floor to the ceiling. Gypsum blocks are somewhat cheaper than tile partition blocks. Very light partitions may be built also of expanded metal or self-centered wire lath, covered with plaster on both sides. All of the above mentioned blocks will permit of the application of plaster direct. Deductions are also made in plastering contracts for openings.