The stone- heat proof material – that fills the bottom of the fireplace or chimney opening , then extends into the room.
The section that extends into the room is for protection, the size of which is governed by building regulation. This may or may not be made of the same material as that within the hearth.
Some further criteria to take into account when choosing and designing are:
a) Fire – soot and smoke and ash – will quickly darken any material so it’s basic common sense to choose one that is inherently dark or which can be cleaned very easily – slate, flagstones, terracotta.
b) Any stone used will need to accommodate expansion joints and for this reason bricks and tiles or flagstones are enduringly popular.
c) Stone floors may run straight into the hearth, although traditionally there has usually been some level of demarcation.
d) The edge of a hearth might be decorative and finished with tiles, or a kerb.
e) For reasons of safety a working hearth is usually surrounded with a low fender – or hearth guard- some sort of metal that will go some way to stop low sparks flying out people falling in.
f) Fire guards must fit within the scope f the hearth stone.
g) Fender seating is a fender made tall enougb to provide comfortable seating around the sides and partially across the front of the hearth stone.
h) As an essential element of the structure, the hearth stone should be in keeping with the architectural style, the materials of the locality and other materials used in the house .
i) A hearth rug that sits in front of the hearthstone is there to catch stray sparks – something that is expendable or accommodating, such as a piece of an antique woollen rug- it doesn’t matter of it has seen better days.