288. Most of the materials employed for protecting the structural portions of buildings from fire and heat, and for filling between the floor beams and rafters, are of earthy composition and come within the province of the mason or plasterer.

The constructive fireproof materials - i.e., those which have to support any weight - most extensively used in this country are : dense, hollow tiles, porous terra cotta tiles or blocks and various concrete compositions, generally combined with steel in the shape of small bars, wires or netting. These materials are used in different shapes and in different ways, both of which are, as a rule, covered by patents controlled by large manufacturing corporations. Most of these manufacturing corporations also take contracts to furnish all the fireproofing material required in the building and to put it in place, leaving the building ready for the plasterer and carpenter. A few manufacturers, however, prefer to confine their business to manufacturing the material, and of late years the practice has become quite general, especially in the East, for the owner or general contractor to buy tiles and the mason contractor on the job to build them in place in the building.

While with contractors of large experience this practice has worked very well, it will generally be found more satisfactory to the architect to have the party that furnishes the material put it in place, as. the responsibility for the proper and prompt execution of the work is then undivided. If the putting in place of the fireproofing must be done by another party, the contract should be let to someone who is familiar with that kind of work and with the material to be employed.

Whichever way the contract is to be let, however, it is well for the architect to specify both the kind and quality of the material to be employed and also the way in which the work is to be done. It is also advisable and customary to require that the floor construction shall be subjected to certain tests before it is accepted.

The kind of material and method of fireproofing that is to be employed should also be decided upon before the framing plans are made, as some systems require different framing than others. Some systems also effect a sufficient saving in dead weight to enable lighter beams and columns to be used than are required where heavy arches of dense tile are used.

If competitive bids are desired to assist in determining the kind of fireproofing to be employed, these can usually be obtained before the plans are completed, the position of the columns determining the spans and width of arches.

If it is decided to use either porous or dense tile arches it is not absolutely necessary to specify any particular make of tile, but the specifications may be written so that any tile may be used which fulfills the conditions therein contained.

The subject of fireproof construction has received a great deal of attention during the past few years, and the increased demand for a safe and economical system of fireproofing has led to the introduction of many systems, nearly all of which, however, may be said to be still in the experimental state. A great many tests have been made of the strength of fireproof floors, but many of these have been conducted in such a way as to be of little value in determining the real strength of the system. As it is not the purpose of this book to enter extensively into the subject of strength of materials, but rather to describe methods of construction, we shall here undertake only to describe the methods of fireproofing most commonly in vogue in this country, referring the reader to the author's "Pocket Book" and especially to a record of tests on fireproof floors published in the Brickbuilder for 1895, for more complete data relating to their strength and to the designing of the metal work.

For lack of space it will also be necessary to confine ourself to the description of the fireproofing of buildings constructed of incombustible materials. The fireproofing of buildings constructed with wooden joist and posts is now almost entirely confined to plastering applied to some form of metal lathing, or to plaster boards or blocks. These will be described in Chapter XI (Lathing And Plastering).

The fireproofing of non-combustible buildings may be divided into three divisions - floor construction, partitions and the casings of posts, girders, trusses, etc. For convenience we will describe the different methods under the above headings first, however, describing briefly the different materials employed in fireproofing.