Terminology & Icons



The above icon shows that this stove is a "nominal" 5kW, that it is "capable of 5kW output" and if that is your requirement then you will not be disappointed (unless you cannot fit your logs in but that is to do with firebox size). It does not mean that this is the maximum performance (it might be but then again the maximum could be 8kW depending on fuel load). When our firebox measurements show that a higher output is possible we add a "+" to the figure. In our experience nominal output is not a particularly useful figure. Please read terminology for "nominal" and "firebox size" below.



This icon means that the stove is approved by DEFRA to burn wood in a smoke control zone. If you cannot see this icon on a stove that stove IS NOT DEFRA approved and therefore not recommended to fit to a 5" liner regardless of collar size. 


This icon means that the stove is approved by DEFRA and a 5" chimney liner can be fitted (unless manufacturer states otherwise). Five inch chimney liners are often easier to fit than 6" chimney liners.



This icon means that the stove has a 6" collar (and so must be fitted to a chimney with a minimum diameter of 6"). 

NB: Although a stove with a 5" collar can be attached to a 5" chimney for the purpose of Building Regulations some manufacturers still state that a 6" must be used (Aga being one such company). 



This stove CAN be sited on a 12mm hearth with no constructional hearth underneath (e.g. 12mm glass hearth on top of carpet etc.) as long as the stove is "freestanding" (not in a recess). If no such icon, or if a stove IS in a fireplace recess, then a full 5" thick constructional hearth is required (often already in situ within fireplace recess). If you are fitting your stove within a fireplace recess and do not have a constructional hearth then it is up to whoever is signing off the job as to whether less than the full 5" is acceptable (for some reason Building regs have different rules for "in recess" and "freestanding outside recess").



Our own method of assessing firebox size. The numbers should enable you to compare one size of stove against another when thinking about maximum heat outputs and maximum log size. Remember that it is the amount of fuel in a stove that determines heat output, see "firebox size" further down in this list of icons and terminology.

Firebox size is most important when choosing a stove. The figures under the max kW rating (the big number in our icon) are the inside useable firebox dimensions: w=width, d=depth, uh = useable height (to a max of 15cm above any device to stop fuel falling out). The bottom figure represents "width x depth x useable height" in cubic cm and it is this figure that you can use to compare one firebox against another.

Note that it is never a good idea to fill a stove and then "slumber for long periods" because the room is too hot (burn less fuel). Nor is it a good idea to always have to "roar" the stove because you purchased a model that was too small (the life of the stove may be shortened).


These are either the minimum air gaps suggested in a stove manufacturer's manual or, in the absence of such information, our own suggestion. There is no safety issues with distances to non-combustibles: the gaps are there to ensure heat from the stove gets into the room and does not just heat up the walls of any recess. DO NOT confuse this with distance to combustibles (much larger numbers!). The last part in brackets means that if you require a sweeping door in your vitreous pipe (because stove cannot be swept through from inside) OR you are using two vitreous elbows to create an offset (OUR FP2, Fitting Pack 2) then a minimum 35cm air gap is required (to fit everything in!).


316 grade (used to manufacture chimney liner): A grade of stainless steel, typically carries a 15 year guarantee. Often chosen if just planning on burning wood light to medium use.

904 grade (used to manufacture chimney liner): A grade of stainless steel, typically carries a 30 year guarantee. Often chosen if burning smokeless fuel, coal or just for the extended guarantee (belt & braces choice). A good choice for heavy users of any fuel.

5”/6”/125mm/150mm: Most modern stoves connect to a 5" or 6" pipe (usually vitreous pipe but sometimes twin wall flue) that carries away the smoke. 5" may be referred to as 125mm and 6" may be referred to as 150 or 152mm. 5" liners are far easier to get doiwn a chimney in most cases.

Air vent: Stoves may require a vent in the room to allow air into the room to replace air use by the stove. See here: http://www.stovefittersmanual.co.uk/articles/do-i-need-an-air-vent-for-a-wood-burning-stove/

Building Control: Although some folks do not partake it is a legal obligation that a stove should be signed off by your local council (Building Control Department) or an organisation such as Hetas (see "Hetas"). See here: http://www.stovefittersmanual.co.uk/articles/building-regulations-for-wood-burning-stoves/

Building Regulations: Legally binding regulations for the building industry. For stoves we generally refer to Document J which can be found here (PDF file): http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADJ_2010.pdf

Carbon monoxide: Invisible gas that kills. Get a Carbon Monoxide detector.

Chimney liner:
Stainless steel tube inserted length of chimney to carry smoke/gases away in the most efficient manner. See also "316 grade" and "904 grade".

Chimney stack: The part of the chimney that rises above the roof of the main building (usually stone or brick).

Closure plate: Plate that seals off the chimney above the stove. See also register plate and: http://www.stovefittersmanual.co.uk/articles/closure-plate-register-plate/

Combustible materials: Materials not designated as A1-fire rated. Essentially brick, stone, steel etc. is non-combustible whilst wood, cloth, plastic etc. is combustible. Plasterboard is, surprisingly, classed as combustible because it breaks down over time when subjected to heat (even the fire retardant pink-plasterboard is classed as combustible for Building Regulations purposes).

Cowl: Sits on top of a chimney pot to prevent rain/birds/down-draughts getting in.

Chimney: Carries smoke and gases safely from fire. If the chimney is a polo mint then the "flue" is the hole. See also "Flue".

Data plate: http://www.stovefitterswarehouse.co.uk/collections/bits-n-bobs/products/data-plate-for-building-regulations

Defra approved/exempt: Stoves that DEFRA (Department Environment Farming and Rural Affairs) have stated CAN burn wood in a Smoke Control Area. Stoves with a 5" flue collar that have DEFRA approval can also be fitted with a 5" liner rather than the usual 6" minimum (makes fitting a liner easier) as long as the manufacturer does not state otherwise. See also "Smoke Control Area" and "flue collar". See here: http://www.stovefittersmanual.co.uk/articles/what-is-a-defra-approved-stove/

The difference between a Defra and non-Defra stove is usually just a small design change to ensure one of the air controls cannot be fully closed (just a tiny amount of air can still get in). This prevents the stove going to the fullest lazy-half-hearted-slumber (which clogs flues with soot and pollutes the environment).

Efficiency: If a stove has 80% efficiency then, to put it simply, 80% of the heat will pass to the room and 20% will go up the flue and off to the outside. The more efficient the stove then the better the flue needs to be (e.g. if a stove is 90% efficient then only ten percent is rising up the chimney and will need looking after to make sure it gets to the top before cooling and therefore stopping rising). High efficiency is not always a good thing as it means less draw and can lead to a lazy fire or a fire that is difficult to get going. High efficiency stoves (88% plus) should not be fitted in short chimneys (bungalows). The higher the chimney the better the draw.

Feathers: The bricks that separate two chimney flues in the same chimney. 

Firebox size: 

Considering the size of the firebox this is the maximum output the stove can produce.

How do we know this? Because we know that a set amount of wood produces a set amount of heat. So from this we can deduce that a set volume of firebox size (in cubic cm) will, if required, emit a set maximum amount of heat.

Stovefitter's formula shows that 2,852 cubic cm of "useable firebox size" should, in most circumstances when burning dry wood, emit 1kW of output. An example below:

DG Ivar 5: Width 27cm X Depth 38cm X Useable Height 21cm = 21,546 cubic cm. 
21,546/2,852 = 7.55 

So the DG Ivar, although rated at "nominal 5kW", has the potential to reach 7.55kW due to its firebox size.

Flue: If the chimney is a polo mint then the "flue" is the hole. See also "Chimney"

Flue collar: The spigot at the top of the stove where the vitreous pipe goes into.

Hardiebacker: 12mm A1-Fire-Rated board for creating closure plates and lining fireplace recesses. Available builder's merchants and some branches Jewsons/B&Q. See here: http://www.stovefittersmanual.co.uk/wp-content/uploads/2017/07/hardiebacker-multifuel-leaflet.pdf

Hearth: The base upon which the stove sits (there are Building Regulations to adhere to).

Hetas: Hetas trained engineers can fit solid fuel stoves and self-certificate (they do not have to use Building Control). Hetas engineers do 3-5 days Hetas training. See also "Building Control".

Liner: See "Chimney liner".

Lintel: A strong arch or beam used to bridge gaps in buildings (e.g. above doors, recesses, windows etc.).

Multifuel stove: A stove that can burn wood and coal/smokeless fuel. Will have a grate and ashpan.

Nominal: of, being, or relating to a designated or theoretical size that may vary from the actual. 

Non-combustible materials: Materials not designated as A1-fire rated. Essentially brick, stone, steel etc. is non-combustible whilst wood, cloth, plastic etc. is combustible. Plasterboard is, surprisingly, classed as combustible because it breaks down over time when subjected to heat (even the fire retardant pink-plasterboard is classed as combustible for Building Regulations purposes).

Register plate: See also "Closure plate.

Sealing plate: An item sold by Stove Fitter's Warehouse. A 9" square plate designed to allow the vitreous pipe to pass through a closure plate in an aesthetically pleasing manner.

SE: Stands for Smoke Exempt. This means that this stove can burn wood in a Smoke Control Area as determined by DEFRA. See "Defra", "Smoke Control Area".

Slumber: When a fire is burning at a very low rate because the air supply to that fire has been restricted. A slumbering stove does not burn off all of the pollutants in the fuel and these pollutants (including soot) will pass through the flue (and potentially block the flue with soot if a stove is slumbered often).

Smoke control area: Areas within the UK where certain materials cannot be used as fuel. Usually cities. DEFRA approved stoves CAN burn wood even in these areas. See "Defra", 
"Smoke exempt".

Smoke Exempt: See SE

Smokeless fuel: Fuel that can be burned in a Smoke Control Area (is similar to coal but has been tweaked in design so as to be less polluting than coal).

Solid fuel: Fuel that is not liquid.

Spigot: Same as flue collar. See also "Flue collar".

Thunderbolts: Thick-shanked screws that do not need Rawplugs. Google "Thunderbolts". I use the ones with tapered heads as these can be countersunk.

Twin wall: Insulated chimney pipe that is generally used to construct a chimney. Often used when a brick/stone chimney is not present. See http://www.stovefittersmanual.co.uk/articles/installing-a-twin-wall-flue-chimney/

Vitreous pipe: The pipe (usually black) that exits the stove. Usually sold in straight lengths (25/50/100cm), elbows (30 and 45 degree) and T-pieces (off back of stove).

Wood burning stove: A stove that can burn wood only. Will NOT have a grate or ashpan. Some "wood stoves" can be upgraded to multifuel with a kit, but others cannot.