take
the ends of joists and distribute the weight along the wall. The plates
bolted on the side of girders are of sizes to suit the width of the
flanges.

The medieval floor (fig. 27) consisted of the framed floor with wood
girders, binding, bridging and ceiling joists; and the underside of all
the timbers was usually wrought, the girders and binders being boldly
moulded and the other timbers either square or stop chamfered.

Flooring is strengthened by the use of strutting, either herring-bone
(fig. 28) or solid (fig. 29). Herring-bone strutting consists of two
pieces of timber, usually 2 in. X 2 in., fixed diagonally between each
joist in continuous rows, the rows being about 6 ft. apart. Solid
strutting consists of 1-1/4 in. boards, nearly the same depth as the
joists and fitted tightly between the joists, and nailed in continuous
rows 6 ft. apart. Where heavy weights are likely to be put on floors
long bolts are passed through the centre of joists at the side of
strutting; since this draws the strutting tightly together and does not
produce any forcing stress on the walls, it is undoubtedly the best
method.

Floors are usually constructed to carry the following loads (including
weight of floor):--

Residences, 1-1/4 cwt. per foot super of floor space.

Public buildings, 1-1/2 cwt. per foot super of floor space.

Factories, 2-1/2 to 4 cwt. per foot super of floor space.

_Local By-laws._--With regard to floor joists in domestic buildings,
the following are required in the Hornsey district, in the north of
London. The size of every common bearing floor joist up to 3 ft. long
in clear shall be 3 in. X 2-1/2 in.; from 3 ft. to 6 ft. in clear it
shall be 4-1/2 in. X 3 in.; from 6 ft. to 8 ft., 6-1/2 in. X 2-1/2
in.; from 8 ft. to 12 ft., 7 in. X 2-1/2 in., and so on according to
the clear span. The Hornsey by-laws with regard to trimmers are as
follows:--A trimmer joist shall not receive more than six common
joists, and the thickness of a trimming joist receiving a trimmer at
not more than 3 ft. from one end and of every trimmer joist shall be
1/8th of an inch greater than the thickness for a common joist of the
same bearing for every common joist carried by a trimmer. For example,
if the common joists are 7 in. X 2-1/2 in. and the trimmer has six
joists trimmed into same, the size of trimmer would have to be 7 in. X
3-1/4 in. The Hornsey council also requires that the floor b