FREQUENTLY ASKED QUESTIONS
Your choice of stove should take into account many factors: the area you are trying to heat; whether or not your stove will be the primary heat source; which fuels you plan to burn (wood burning stoves will generally have a larger firebox with a wood ‘tray’, multifuel stoves will have a grate on which both wood and smokeless fuels will burn); safety factors such as clearances to combustibles; whether or not you have an existing chimney or fireplace, as well as aesthetic style considerations.
Some stoves, especially models from Nordic countries where wood-burning is ubiquitous, are only able to burn wood. To burn coal, a grate and some means of removing ash (usually an ash pan) are required. It is now commonly accepted that wood burns just as well, if not better, on a grate. Many of our favourite stoves are supplied ready to burn either fuel as standard. Such a dual-fuel appliance is known as a “multifuel” stove.
Yes. The chimney is in effect both ‘exhaust pipe’ and ‘engine’ for your stove. It needs to terminate in clear air, and be tall enough to provide the necessary draught. Ideally it should be well insulated to keep flue temperatures above the dew point, but engineered to cope with abuse. Please ask for our advice and feel free to show us your plans before you build.
The chimney can be of traditional brick or stone construction, preferably lined with pumice flue liners. Clay is a poor lining material which struggles to keep a chimney warm. The resulting tar-like condensate then runs down the non-porous surface and into your fireplace or stove, often accompanied by staining and an acrid stench emanating from the chimney. Refractory concrete has also been commonly used, but for similar reasons is not an ideal lining material.
It should be remembered that a traditional chimney stack requires a proper foundation; thus whilst it will almost always be the most appropriate choice for new build, blending in with the rest of the building materials, it is usually the most expensive option if one is adding a chimney onto an existing property.
Less expensive options include several proprietary prefabricated block chimney systems such as Isokern DM, with one block stacked one on top of the next Lego-fashion. However, the most frequently-used method for providing a new chimney is to use a top-quality prefabricated twin-wall insulated stainless steel system such as Chimaster MF. These chimneys can usually be installed either up through the inside of a building, or externally fixed to the outside wall.
We can advise you on the most appropriate flue options for your installation.
If you feel competent, yes, but it is essential that you fully comply with Building Regulations and obtain the necessary Building Control approval. An application should be made to Building Control prior to the work being started.
Alternatively, using a HETAS registered installer guarantees a compliant installation, and will save you the expense and bother of obtaining Building Regulations Approval, not to mention the headache of re-doing the whole job if it fails to comply. All our installation team leaders are HETAS registered.
In October 2010 the law changed with the further revision of Section J of the Building Regulations. The revised Approved Document J (AD.J) provides guidance on how one may comply with the regulations.
Under the new regulations, work on fireplaces, hearths, flues and chimneys, and the installation of wood burning or multifuel stoves are all controlled building operations. Unless the work is carried out by an approved installer such as ourselves under the HETAS ‘Competent Persons’ scheme, customers are advised that an application should be made to Building Control prior to the work being carried out.
In new build, Building Regulations have required since 1965 the installation of suitable Class 1 liners in a masonry chimney. These are usually composed either of clay, refractory concrete or pumice. We frequently advise the re-lining of many chimneys where poor materials have been used, or where they have been incorrectly installed. A common mistake made by many builders in the UK has been to install clay liners upside down, practically guaranteeing the leakage of creosote out of the chimney and into the fabric of the building.
Before installing a stove into an existing unlined chimney, it should be inspected by a Competent Person to determine whether it is safe to use without a liner. Older chimneys generally require lining and insulating, and the material used should be appropriate for the appliance being fitted. It is, for instance, both dangerous and illegal to connect a light duty flexible gas liner to a solid fuel appliance. The appropriate diameter liner should also be used, both to achieve the correct chimney draught, and to ensure that all the products of combustion are safely evacuated.
The material most commonly used for retrospective lining is stainless steel. Where an existing flue is perfectly straight, rigid sections of fluepipe can be used: but where, typically, there are bends in the brick flue, a flexible liner is more appropriate. This is available in two grades of stainless steel: 316 and 904L, the latter being more corrosion-resistant and suitable for use with approved solid fuels. The liner is normally surrounded with an insulating material – most commonly “Leca” (small beads of lightweight expanded clay aggregate), or mineral fibre such as high temperature Rockwool. It is important that a practical cleaning access is provided to facilitate regularly chimney sweeping. Any visible stainless steel is usually sprayed with high temperature paint to match the stove.
Yes. With an insulated liner installed, flue deposits should be much less than without one: but regular annual or semi-annual sweeping not only keeps the liner clean, but confirms that dangerous tarry deposits which might result in a chimney fire are not being formed. Regular sweeping is your best insurance policy against chimney fires, and knowing the flue is clean throughout its length provides peace of mind.
At least once a year, and more frequently if you are burning solid mineral fuel or moist wood, or if you are not burning your wood cleanly. Ideally the chimney should be swept before, during and after the heating season. Sweeping reduces the risk of a chimney fire, and optimises the performance of your heating appliance. Always use a qualified sweep who will leave you with a Certificate of Chimney Sweeping for Insurance Purposes
For new-build, a ‘constructional hearth’ in front of the chimney breast of at least 500mm (20”) from front to back is required. Where there is a concrete floor slab, this is usually sufficient; but with a suspended wooden floor, the floorboards / joists must be cut back and concrete used to build up a constructional hearth, usually from ground level. The ‘finish hearth’ is then laid on top of this using tiles, bricks, granite, slate or marble; this finish hearth must extend at least 300mm in front of a stove, and at least 150mm on each side.
Where there is no chimney breast, a freestanding constructional hearth must have minimum dimensions of at least 840 x 840mm: however, there should still be at least 300mm of hearth in front of the stove, and at least 150mm on either side of the stove, and at least 150mm behind the stove (or extending back to a suitable heat-resistant wall), so the actual dimensions may be greater for some stoves. A new relaxation to the regulations allows the constructional hearth to be dispensed with and a minimum 12mm thickness of non-combustible material to be laid over a wooden floor, providing the temperature under the stove never exceeds 100 degrees C during normal operation.Every installation is different, and individual requirements for fluepipe therefore vary considerably. For this reason, flue materials are never included in the basic price of the stove, but are supplied as necessary for each situation.
It is essential that combustion appliances have enough oxygen to enable the fuel to be burnt safely and efficiently. Approved Document J of the Building Regulations specifies the size of permanently open air supply that must be provided for the different types of fuel burning appliance. For existing dwellings, no air vent is required for wood burning or multi-fuel closed stoves with a rated output of 5kW or less. For every additional kW, Building Regulations specify 550 mm2of permanent ventilation. However, for new build, the increased airtight construction required to satisfy Approved Document L means that an air vent is now required for all stoves, irrespective of output.Where a suitable air vent is not already present, replacement combustion air can either be taken from the ventilated airspace below a suspended wooden floor via brass grilles, or one or more circular vents or conventional airbricks can be installed through a suitable outside wall. Some stove manufacturers make provision for air to be drawn from outside and fed directly into the combustion chamber of the stove, and for new build this is often the most appropriate method. We can advise you on the best way to ensure your permanent ventilation is suitably installed.
Building Regulations and stove manufacturers specify minimum clearances between the appliance and its flue and combustible materials. This applies to wooden beams, fire surrounds and less obvious materials like plasterboard. It is important to observe these clearances to enjoy the safe use of your stove. However, an informed selection of the correct stove, heat-resistant materials, insulated fluepipe, stove placement and fireplace design, can often allow the inclusion of wooden beams and surrounds. We can advise you on all the possibilities and offer bespoke solutions. We stock an extensive range of aged wooden beams in our showroom, and have long experience in integrating them safely into your fireplace design.
Some people have distant childhood memories, or perhaps more recent personal experience, of an open fireplace which was notoriously difficult to light. A modern wood burning stove is in fact very easy and quick to get going, and the best materials are freely available: balled-up sheets of yesterday’s newspaper, pieces of cardboard, and a few handfuls of dry kindling wood. One match should be all that is needed, and within a couple of minutes the fire is roaring away and small logs can be added.
The cardinal rule is this: whatever type of wood you burn – be it softwoods such as pine or larch, or hardwoods like oak, beech and holly – the dryness of the wood is by far the most important factor. Wood with a high moisture content will be much more difficult to light: once alight, it will provide little useful heat because most of its latent energy is being used to drive off the moisture as steam, and the risk of cool moisture-laden flue gases condensing in the chimney are greatly increased. Such condensates are potentially dangerous if they catch fire, and are very likely to produce tarry stains and smells if they seep through the chimney brickwork.
Wood must be “seasoned” for at least one summer before being burnt — and seasoning for two summers is preferable. To season wood properly, pieces which are too long need to be sawn to stove length and tree trunk ‘rounds’ need to be split. The wood then requires maximum exposure to sun and wind: the sunnier and draughtier the position of the woodpile, the better. The top should be covered to stop rain soaking down through the pile, and logs should be stacked with gaps to allow air movement. Storing unseasoned wood in the garage or in a closed shed is not recommended: it will not be able to dry out easily, and wet timber will just encourage rot and the growth of fungi. Unused greenhouses and conservatories that are exposed to the sun can make excellent ‘solar driers.’
We highly recommend purchasing a Moisture Meter to check your logs. Ideally, they should read 20% or less. Take the reading from the inside of the log by splitting a log in two.
There are two basic designs of wood burning and multifuel stove: the “inset convector”, and the “freestanding” stove. Inset stoves are designed to be ‘built in’ using brick, stone, granite, marble or some similar non-combustible material to surround them, and they often incorporate internal air channels and heat exchangers to transfer heat back into the room by convection. So long as the fireplace recess is marginally larger than the dimensions of the stove firebox, such a stove can usually be built into an existing or specially prepared opening.
Freestanding stoves, however, are designed to have air circulating all around them, and it is especially important that there is as much space above a stove as possible, with the ideal being something between 300mm and 450mm. A minimum of about 100mm on either side and 25-50mm behind should also be allowed. Where the space above the stove would have to be much less than 300mm, it would be better either to position it in front of the opening, or at least half in and half out (but always remembering the building regulation requirement for the minimum 300mm hearth extending in front of the stove).
Chimneys or flues added to buildings within Conservation Areas generally require planning permission, and listed buildings require listed building consent. It is always advisable to check with your local authority whether they require an application to be made before deciding to proceed.
The word ‘Chimney’ refers to a solid built structure and the ‘Flue’ is a passageway or duct for the venting of smoke or related gasses. The ‘Stack’ is the part of a chimney that rises above a building, and the chimney ‘Pot’ is placed on top as a cheaper method of adding a little more height.
Having your chimney modified to increase the updraught is not a new idea; the discovery is that of Sir Benjamin Thompson – Count Rumford, around the 1790’s. His method known as ‘The Rumford Fireplace’ increased efficiency and airflow by simply narrowing and restricting the flue with a choke.
The modern day stove was created by Benjamin Franklin around 200 years ago, though his version sold poorly as it needed to improve on efficiency and it was also a little flawed in design as it cooled the smoke far too much before it entered the chimney. His design did not have doors on the front, nor could you use it to cook food.
