Pease's Patent, Figs. 53IG and 532H, a very ingenious arrangement, consists of sheet iron or steel tubes, so constructed that a cup, as it were, is formed to cany the concrete as a centre; at the same time the whole is bound into a solid mass; these tubes, which can be used as long as 12feet, rest on the flanges of the girders, and as a protection to the underside slabs can be hung up by bolts, as Fig.. 532c.
There are many other similar floors in use, which are perhaps equally as good as those hereinbefore enumerated; the general disadvantage of most of them is their disposition to conduct sound from floor to ceiling, necessitating the use, very often, of counter-ceilings, with an intermediate space, which is the best non-conductor. It will be noticed how most of them endeavour to attain this end in the floor itself.
The floor-boards above these systems are fixed to dove-tailed wood fillets, or Wright's patent breeze dove-tailed blocks, embedded in the concrete, and made level as the ordinary joists, similar to Fig.. 533; while the wrought-iron members, unprotected underneath, are, or should be, covered with patent wire-wove material, which keeps up the concrete casing, and forms a key for the plastering for ceilings and ornamental beams.
Fireproof Partitions are constructed with tubes on Pease's principle, or by hollow blocks, as Fig. 532j, which are light, and made that they lock together, forming a solid mass - this is Picking's arrangement; and Banks has a patent consisting of steel X-shaped standards, with a double row of helical lathing, Fig. 532K and Fig. 532L, plastered similarly to the ceilings in his patent floor.
The blocks may be of any regular thickness from 1 1/4 inches up to 2 1/2 inches, the ordinary kind being from 9 to 18 inches long and about 3 inches wide; and it is absolutely necessary that they be truly square, so that when laid they fit together well. Moreover, it is most important that they are thoroughly dry, and they should not be brought on to the building until the cement screed or bed is quite dry, and they are actually required for use. Very often good dry blocks are brought into a building which cannot be really dry; and whilst they are waiting to be laid, they absorb the moisture of the building and surroundings, with the result that they swell, and in this condition they are laid, and as soon as they and the building get dry they shrink, and show large cracks, and in many cases (hey even rise up.
A wood-block floor can be laid to designs and patterns in any kind of wood, and they are kept down in their positions by a solution containing pitch, resin, and other patented mixtures, which are of a Sticky nature when hot, and on cooling are so cohesive that they keep the blocks and screeding together.
There are several patent systems of laying these blocks, the general principle being to form keys or dovetails - this end being attained by a triangular sinking or groove made in the edges of the blocks, close down to the bottom, so that the solution on the bed can be pressed up into the grooves formed between the blocks. This dovetail keying is also formed by small iron channels embedded in the cement screeding. Another idea is to keep down the blocks by dowelling them together, and Stockholm tar is used to make them adhere to the cement bed.
In hospitals and other similar buildings teak or other hard-wood ordinary floor boards are secretly nailed directly on to the cement screed itself without the fillets shown in Fig.. 533.