178. In Fig. 85 is shown a system of floor construction, which is known as the Fawcett ventilated floor, by the use of which a saving of one-quarter of the dead weight is effected.

Ventilated Floors 212

Fig. 85.

The pieces are made of dense fireclay tile, the upper part a being semicircular, and cut, as at b, to rest on the beams; this cut-out is sufficient to leave a 1/2-inch air space between the beam and the flat under surface c, which extends to the middle of the support, as at d, forming, with the air space, a thorough protection; the under side of c is grooved so as to form a good key for the ceiling plaster. For this floor, the beams are spaced 2 feet apart, more being required than with other systems. Owing to this close spacing of the beams, very light ones can be used, 5 inches being the usual depth for spans not over 15 feet; the floors can, therefore, be made considerably thinner than in other systems; 10 inches is the total thickness of a floor having 5-inch beams. This is an important saving, amounting to 6 or 8 inches on each story. Another advantage is that these floors can be laid without centers, and by ordinary laborers.

When the tiles are laid, concrete is placed on them, resting on the lower flange of the I beams, between the curved parts of the tile; when set, the concrete between each piece acts as a beam, transmitting much of the floor load directly to the steel framing.

The great advantage of this system is the thorough ventilation afforded by the peculiar form of the tiles, the interior spaces being in continuous connection with the external air, which is admitted through air bricks in the outer walls. At (b), Fig. 85, is shown a longitudinal section through the tile, showing clearly the air spaces a, the hollow brick b, and the method of supporting them at the walls, as at c.