6.8.18 All – fireplaces and hearths
Fireplaces and hearths shall safely accommodate the appliances for which they are designed.
Combustible material should not be placed under a constructional hearth unless it is:
- to support the edges of the hearth
- at least 250mm from the material to the top of the hearth, or
- separated from the underside of the hearth by an air space of at least 50mm.
Fireplace recesses should be constructed of solid
non-combustible material as shown in the figures (dimensions
are based on a 125mm concrete hearth below an open
fire). The space between a fire back and masonry forming
the recess should be filled with vermiculite concrete (1:4,
lime:vermiculite with water).
Figure 17: Fireplace recess — external cavity wall projection

Figure 18: Fireplace recess — external cavity wall with dimensions

Figure 19: Fireplace recess — internal wall with dimensions

Figure 20: Appliance recess with raft lintel (freestanding heater)

Figure 21: Lintelled opening for inset open fire (chimney throat insert)

Last updated: 2nd January 2025