th a better grade of brick or perhaps another kind. Frequently,
also, tile will be combined with the brick finish as a hearth or facing.

[Illustration: A cross-section showing the construction of a
large stone fireplace with slightly arched opening]

A support for the hearth is usually obtained as indicated--by bringing
what is called a "row-lock" or "trimmer" arch between the foundation
masonry of the chimney and a pair of floor joists set out at the proper
distance, depending upon the desired width of the hearth. While this is
the customary method, occasionally a support is secured in some other
way, such as corbeling out from the masonry foundation, or by extending
two short projections of this masonry from the bottom up at either end
of the hearth and throwing an arch across between these. Upon a bed of
cement the hearth bricks themselves are laid, usually flush with the
floor, although occasionally enough higher to permit a beveled molding
strip to cover the joint between brick and floor more closely. In some
cases the hearth itself is raised the full thickness of a brick above
the floor, as in one of the photographic illustrations shown.

The width of the hearth is ordinarily made about sixteen or eighteen
inches beyond the face of the opening with the average size fireplace,
twenty inches or even more with larger ones. This width should be
increased, of course, if the opening is made considerably larger. The
question of materials for the hearth and facing will be discussed in the
next chapter.

The chimney itself should extend at least a foot or two above any nearby
roof ridge and it should work without any cowl, whirligig or other
device of that type on the top. There is no great objection to having
the opening a horizontal one at the top of the chimney, although in that
case if the flue is nearly straight throughout its course, some rain
will find its way down to the hearth in a hard storm. In most cases
there is enough bend in the flue to prevent this, and if not it may be
avoided by covering the top of the chimney with a stone and having the
openings vertical ones on all four sides just under this.

All of the brickwork throughout chimney and fireplace should be laid in
first-class cement mortar which consists of one part Portland cement to
three parts clean, sharp sand. Although lime mortar was used in all
brickwork up to recent years, it is not durable, particularly in the
vicinity of heat.