As a large proportion of fires in residences originate in the chimney,
it is well to have this part of the house as nearly fireproof as
possible. It can be made entirely so by building it of concrete. If
this is not convenient, at least let the chimney cap be of concrete.
[Illustration]
These caps are cast in one piece, on the ground, and in any shape
desired.
The outside form is a wooden box, with inside dimensions corresponding
with the outside dimensions of the desired cap. Usually the cap is 6
inches thick, and has an “over-hang” or “drip” extending on all sides
beyond the outside of the chimney.[3] Thus, if top of chimney, over
all, is 18 inches square, make outer form 22 inches square, an extra
allowance of 2 inches on all sides, thus obtaining a cap that will have
an “over-hang” of 2 inches all the way around.
[3] A simple method for building a chimney entirely of concrete is
described on page 50.
The inside form may consist of a piece of terra-cotta tile. If more
than one opening is desired in the cap, use two pieces of tile or as
many as there are to be openings.
Mix concrete 1: 2: 4, the mixture to be a thoroughly wet one. Place
in the form, after greasing outside of terra-cotta so that same may
be easily removed. Leave undisturbed for two days. Remove forms and
place cap in position, attaching it to the brick chimney with a cement
mortar, one part cement to one part sand.
[Illustration]