Hearths for stoves - in Document J, pages 31-33
Stove building regs pages:
Stove building regulations intro
Installation and Building Control
Stove hearth sizes
Flue outlet heights
Ventilation for stoves
Flue pipe - distance to combustibles and heat shielding
Flue pipe - recommended lengthTwin wall flue - boxing in
Lining existing chimneys
Hearths in general
The idea of a hearth for a stove is that the stove sits on a slab of non-combustible material that protects any combustible materials underneath and around the stove from the heat of the stove and from any burning fuel that might accidentally fall out from the stove.
If burning fuel falls from the stove then the hearth should be of sufficient size that it lands on the hearth and not on the floor, carpet, or other combustible material.
The edge of the hearth should be at a different level from the floor to clearly define the safe perimeter - you can easily do this by making the hearth higher than the rest of the floor.
We can supply a range of floor plates
(a floor plate is also a hearth) made from glass, steel and resin.
The stove must sit on a hearth of non-combustible material extending a minimum of 150mm (6") out from the stove at the sides and 300mm (12") in front.
Technically this 300mm distance can be reduced a little if the stove is not designed to be run with the door open, but in practise just about all stoves can be run with the door open so we recommend using 300mm to the front of the stove as a baseline.
If the hearth is on a combustible floor it must be at least 250mm thick or...
The hearth may be 125mm thick if there is a 50mm air gap underneath it or....
If a stove has been tested and shown to not raise the hearth temperature to over 100 degrees centigrade then a 12mm hearth may be used.
If the hearth is on a non-combustible floor (for example and concrete floor slab) then the total thickness of the hearth and of the non-combustible floor must be 250mm or...
125mm thick with a 50mm air gap underneath or....
Again if a stove does not raise the hearth temperature to over 100 degrees centigrade then a 12mm hearth may be used.
Hearths for freestanding stoves
The minimum hearth size for a freestanding stove is 840mm x 840mm, unless the stove is installed in a recess.