SAFE DISTANCES TO COMBUSTIBLE MATERIALS AND HEAT SHIELDING FOR STOVES IN A NEW BUILD AND TIMBER FRAMED HOMES

Ensuring that your new stove and its flue maintain a safe distance to combustible materials, some of them concealed, is of paramount importance. Some issues can be avoided by careful consideration of the stove type and the individual manufacturer's safe distances declarations – which can vary greatly, as well as how the stove will eventually be installed and exactly where it will be placed. If you're planning on building a Class 1 chimney with a traditional fireplace, then in terms of safe distances to combustible materials, there is not much to consider compared to a free-standing installation.

With a free-standing installation you'll need to create a bespoke chimney with a twin wall flue system and this will no doubt introduce a number of issues regarding its proximity to combustible materials. The flue system will either need to exit the building through the wall and up the side of the house close to the eaves or alternatively through the ceiling, two if it's a two-storey house, and then through the roof. However, with some careful consideration, and possibly some minor compromises – provided you plan ahead, you can ensure that the flue system will safely route its way through your house.

Single skin vitreous enamelled flue pipe would need to be kept clear of combustible materials a minimum of three times its diameter – that's 375mm for 125mm (5") and 450mm for 150mm (6") diameter flue pipe, which would clearly be impractical and is why it should only ever be used sparingly to connect the stove to a concealed flexible liner (within a Class 1 chimney) or to a complete twin wall flue system. Twin wall, with its double skin construction and insulation sandwich, will deliver greatly reduced safe distances to combustible materials compared to the stove and any single skin connecting pipe. This is usually somewhere between 50 to 70mm from the twin wall pipe surface which will easily allow a 150mm diameter twin wall pipe (overall diameter 200mm) to maintain safe distances through the 400 to 600mm standard gaps between ceiling and floor joists or roof rafters.

Due to the type of construction, many walls in new build homes could be classed as combustible because of their plasterboard finish and / or timber stud inner leaf. You must bear in mind therefore that some stoves can require safe distances to combustible materials of up to 500mm at the rear which would clearly be impractical, as well as unattractive looking, without taking additional measures to reduce such distances. Even those stoves with standard or optional heat shields can still require a significant space.

In order to reduce the installation footprint and also have complete control over how close the stove can be placed against the wall then the safest option, if you can, is to design and build in a non combustible finish behind the stove which protects at the very least the appropriate area of the wall behind the stove and connecting flue pipe. One of the simplest and most cost-effective solutions is to use a suitable high temperature fire-board instead of plasterboard, ensuring that the manufacturer's instructions are followed – but beware, it is not unusual for cracks to eventually appear between the various joints. In our view by far the two best solutions for a free-standing stove is to create an attractive back drop constructed full height from floor to ceiling with a sympathetic non combustible feature material such as stone or tile. Alternatively for ease of installation and complete peace of mind choose decorative plain or patterned vitreous heat shield panels from the stunning specialist Vlaze collection. These ensure that the required BS8303 air gap is always maintained. Check out the exceptional Vlaze range of decorative vitreous enamelled heat shields here.

When considering any bespoke heat shielding for a stove in a free-standing installation (one that's not situated within a fireplace recess) you must refer to BS8303 which outlines the protection needed to be given to combustible materials in order to comply with Building Regulations Document J, Section 4.
Regarding heat shielding, in summary BS8303 states...

• The stove should not have a nominal heat output greater than 7.0kW (NB higher output stoves may need to meet increased safety standards not specifically covered in BS8303).
• The heat shielding should be manufactured from suitable non-combustible materials, for example 1.5mm minimum thick steel, appropriately fixed using non-combustible fixings.
• A 25mm air gap should be maintained between the rear surface of the heat shield and the face of the protected combustible material.
• Heat shielding panels should be open at the top and bottom to provide a flow of air through the gap between the heat shield and the protected area to prevent heat building up.
• Minimum distance of the heat shield to the closest point of the stove should be 95mm (unless the stove manufacturer stipulates less for their stove when it is fitted with their rear heat shield)
• Minimum distance of single skin vitreous enamelled single skin flue pipe to the heat shield should be 1.5 times its diameter: 188mm each side for 125mm (5") and 225mm for 150mm (6"). In order to reduce this you could leave out the single skin connecting pipe and use twin wall (with the appropriate adaptor) straight off the top of the stove.
• Minimum distance from the top of the stove or single skin flue pipe to the top edge of the heat shield should be 300mm.
• The overall width of the heat shield should be at least the width of the hearth which should conform to building regulations. The minimum width for a free-standing hearth is 840mm and in the case of wide body stoves the hearth should also provide a minimum distance of 150mm from the sides of the stove.

Hetas have provided some useful diagrams and guidance which further illustrate how to conform to BS8303 heat shield requirements and you can click the link here.  https://www.hetas.co.uk/heat-shielding-requirements/

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