Safe Distances to Combustible Materials

Due to the levels of heat emitted from flue pipes and stoves, it is essential these are installed at a safe distance from any combustible material which could catch on fire from heat transfer (typically wood, carpets and soft furnishings).

Clearances to combustibles vary from Single to Twin Wall flue and from stove to stove and are set out in Approved Document J of the Building Regulations (England & Wales) or by the stove manufacturer based on the test results of the appliance.

It is not uncommon to have to amend your original plans for where you wish your stove and flue to be installed once safe distances to combustible materials are taken into consideration however, they are solely designed to keep you and your home safe as heat transfer into wood can go unnoticed until combustion.

Single Wall Stove Pipe (Vitreous Enamelled)

As single skin stove pipes have no insulating material, they transfer a lot of their heat to the outer surface which can become incredibly hot. Therefore, it stands to reason that to be safe you must maintain quite a substantial distance between these pipes and combustible materials. Building Regulations state this clearance must be at least 3 x the internal diameter of the flue pipe as illustrated below. However, if the surface is constructed from a non-combustible material or you have shielded it with fire proof boarding such as our Vermiculite Boards, then this distance can be reduced to only 1.5 x the internal diameter of the flue pipe.

For example, a 5″ (125mm) internal diameter single wall pipe must have a safe clearance from combustible materials of 15″ (3 x 5″) and 7.5″ (1.5 x 5″) clearenace to non-combustible materials.

SW Distance to Combustibles

Twin Wall Insualted Flue Pipe

Due to the layer of insulation between the inner and outer skins of a twin wall flue pipe, the heat emitted from these is greatly reduced and therefore, so is the safe clearance to combustible materials. For our Shieldmaster Twin Wall, you must maintain a 60mm clearance all the way around the pipe and for SFL Sflue, it is a reduced 50mm distance. In reality, this means the size of hole you would need to cut in a combustible wall or roof for 125mm Shieldmaster Twin Wall would be 295mm across (175mm outer diameter + 60mm + 60mm).

This figure is included within the designation number applicable to your brand of Twin Wall pipes. There is no regulation for the distance of Twin Wall flue pipes to a non-combustible material.


Stoves require the greatest clearance to any potentially combustible material but this does come down to the individual brand and model of appliance and is stated on the data plate. This measurement could be in the region of 600mm, 800mm or even greater and may be different for the sides and rear. There is no regulation for the distance of a stove to a non-combustible material, only clearances recommended by the manufacturer (usually in the region of 100mm to allow air to pass around the appliance).

Data Plate

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