Advice and FAQs

We're asked many questions by our customers, some of which are listed below. Please click a question for the answer:

» What size and output of stove do I need?
» Do I require a chimney?
» Is planning permission required?
» Is lining an existing chimney necessary?
» What flue size should I have?
» How to choose your logs
» Seasoning wood
» What is a moisture meter?
» What happens if I burn green or unseasoned logs?
» What is the best type of wood to burn?
» What coal can I burn?
» Is it best to buy a wood burning or Multi-fuel stove?
» Cast iron or Steel stove?
» Do I require a hearth?
» Can I install my own stove and chimney system?
» Can I use the stove to help run my central heating and hot water supply?
» Do I require an air vent to be fitted?
» What information is useful to bring along to the showroom?
» How often do I need to sweep my chimney?
» Can I have a Wooden Beam or surround - distance to combustible materials?
» What are smoke control areas and a DEFRA exempt appliance?

 

» What size and output of stove do I need?

It is important to try and get the most appropriate output for the area you are trying to heat. If you have the stove in a fireplace it is important to ensure it fits into your fireplace opening with sufficient clearance. The online calculators are a useful guide but other factors will need to be taken into account. For example the insulation value of the walls, whether the windows are double or single glazed and if you have high or vaulted ceilings. Having a stairs in the room will also affect the distribution of heat in the room and so will archways or door opening into other rooms. It is always best to have a survey by a registered engineer.

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» Do I require a chimney?

Yes, a wood or multifuel stove must be connected to a chimney that is suitable for use with solid fuel, which is often called a "class 1" chimney. This can be traditional brick or stone construction sometimes with clay, refractory concrete or pumice liners. If no chimney is present then there are different types of chimney products and construction available depending on your property. - see building a new chimney section.

Please ask our advice for the best solution for your property and feel free to bring in your plans, best before building has started.

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» Is planning permission required?

Planning is not required for installation of a stove but may be required for a new chimney. It is always best for you to check with your local authority to confirm if permission is required. More details are given under the planning permission section.

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» Is lining an existing chimney necessary?

It is not always necessary to line your chimney but it depends upon the condition of the existing chimney and the heating appliance it will be used with.

It is common to find that old chimneys are in a poor condition and can leak fumes, particularly if the flue is not lined. Over time hot smoke, tars and acids eat into the chimney walls and erode mortar joints causing staining to the exterior stone or brickwork, and leakage of dangerous fumes into the property. Large and uneven flues can also create poor up draught causing smoke to blow back into the room.

It was only in 1965 that Building Regulations required new chimneys to be built with suitable flue liners to protect the chimney structure and provide a smooth flue for efficient performance of the heating appliance.

Old chimneys should be checked by a professional competent person before being put back into use. This should identify what work or repairs are needed. It is prudent, and often essential, to fit a new liner to provide a smooth sealed flue way that ensures maximum safety and efficiency. Most stove and fire manufacturers require their appliances to be used with chimneys that have a suitable liner and flue size to match the appliance.

Topstak supplies a choice of systems as shown in the relining old chimneys section.

Many existing chimneys have been constructed with clay liners. Clay is not an ideal material for use with stoves burning wood as the material is non porous and poor at keeping the chimney warm. This causes a tar like substance to form and run down the liners in to the fireplace or stove. This substance can leak out over time causing staining and also an acrid smell.

A new build property with a masonry chimney construction that has been built correctly should not normally require lining assuming it passes the relevant tests and the flue size suits the stove being installed.

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» What flue size should I have?

The size depends on the make of stove and this should be given in the manufacturer's installation instructions. A minimum flue size of 150mm (6 inches) is required for most small stoves, but always check the installation instructions. However, the 2010 edition of the Approved Document J permits a minimum flue diameter of 125mm for a closed appliance of up to 20kW rated output which meets the requirements of the Clean Air Act when burning wood, which is normally called an "exempt appliance".

Beware of anyone who says you can use a 5 inch (125mm) diameter flue liner with a wood burning stove if they cannot prove that the stove is an exempt appliance and this flue size is permitted in the manufacturer's instructions. More details on Flue sizing are given in the Regulations section.

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» How to choose your logs

Choosing the best log length is important. This is determined by the type and size of the stove or fire. A good start is to check the user instructions for the appliance, which should recommend a suitable log length. For example Clearview recommend a 15 inch (375mm) log length for their Vision 500 stoves. This ensures you get a good long clean burn by having a log that's sized to suit the firebox. The cross section of the logs is also relevant and Clearview give good advice that logs over 5 inches (125mm) in diameter are best split unless really dry.

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» Seasoning wood

Green or freshly cut logs will have a very high moisture content, which is not good for burning and will cause all sorts of problems such as tarring of the flue and very low heat. This is why the logs need to be seasoned to reduce the moisture content to below 25% or less depending on the appliance. To achieve this wood should be cut and split into the required logs size, then stored under cover with good all round air circulation to allow the moisture to evaporate. This can take a year or more depending on the type of wood. Storage under cover means there is a covering above the wood to shed off rain, just like the Topstak log stores. Logs will not season very well in a closed shed, garage or stable as there will not be enough air circulation. It is a good idea to invest in a moisture meter to help check how the logs are drying.

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» What is a moisture meter?

This is a great tool for checking the moisture content of your logs.Moisture Meter

There are different types including the Euroheat meter shown to the right which is one of our best sellers!

The two sharp prongs are pushed into the wood to provide a moisture reading that is shown as a percentage. The 36.9% in the photograph is too high so the logs will have to dry out for a lot longer to get down to at 25% or less.

The reading has to be taken at the right place as shown in the operating instructions.

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» What happens if I burn green or unseasoned logs?

Burning green or unseasoned logs must be avoided as it creates many problems. When logs with high moisture content are burnt they generate very little heat as most of the energy is being used to drive off the moisture in the form of water vapour and steam. This mixes with the resins and products of combustion to create tar that can damage the appliance and block the flue, which in turn risk the dangers of a chimney fire or fumes escaping back into the room. Burning green or wet wood is very inefficient and also creates lots of polluting smoke, so must always be avoided.

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» What is the best type of wood to burn?

The first answer is dry wood is the best and always check the appliance manufacturer's operating instructions. Seasoned hard woods such as ash, oak, beech, birch, sycamore or hawthorn tend to give a longer burn as they are denser than softwoods. Softwoods tend to burn quicker, so are usually used for kindling sticks. Some types of wood such as spruce and horse chestnut spit badly making them a hazard in an open fire.

Treated timber must not be used as it can produce harmful fumes, which is why most appliances manufacturers say they must not be burnt. Some even advise against burning joinery off cuts as they can produce very high temperatures, which in some cases can damage the stove.

Clean processed wood is also available in the form of briquettes or compressed logs, such as the excellent Megatherm logs that we sell. These can burn very hot so care is needed to avoid over firing.

If you intend to burn wood check that you are not in a smoke control area, and if you are make sure you have an exempt appliance, otherwise you could be breaking the law.

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» What coal can I burn?

As there are so many different types of coal (or solid mineral fuel as it is often called) you need to check the appliance manufacturer's operating instructions. Ordinary house coal is not usually considered suitable for use on a closed stove. This is why smokeless fuel is often suggested particularly in smoke control areas, and if you are in one of these areas make sure you use an approved smokeless fuel. Details on "approved" fuels are given on the HETAS website - http://www.hetas.co.uk

Many appliance manufacturers say that "Petro coke" must not be burn as it produces an incredibly fierce heat that usually damages the appliance.

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» Is it best to buy a wood burning or Multi-fuel stove?

Wood burns best on a flat bed of ash with air coming down onto it. Solid mineral fuel or coal as it is usually called requires a slotted grate with air coming up from underneath. If you are only going to burn wood it is generally best to go for a wood burning only stove but most multi-fuel stoves will still burn wood well. If you are going to burn solid fuel then a grate with external riddling to shake the ash down in to the ash pan is a good choice.

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» Cast iron or Steel stove?

A Cast Iron stove will take longer to warm up but will retain the heat a bit longer than steel, whereas steel will heat up quicker but not hold the heat quite so long. There is not much difference between the two materials in performance. What is important is to choose a stove that is designed and made to a high standard with a really efficient superheated air wash system.

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» Do I require a hearth?

A hearth is always required and more details are given under hearths in the Regulations section.

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» Can I install my own stove and chimney system?

It is possible to install your own stove and or chimney, but you must comply with the Building Regulations and obtain the necessary Building control approval, if you do not the consequences can be serious as explained in Failure to Comply. It is generally recommended that you use competent persons to do the work, such as a HETAS registered installer

All our installers are HETAS registered.

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» Can I use the stove to help run my central heating and hot water supply?

Yes, many stoves feature the option of a boiler to provide domestic hot water and or central heating. It is important to seek the advice of a qualified plumber to calculate what boiler output is required for your needs, such as domestic hot water and or radiators. The plumber will also need to take into account heat loss from pipework and work out what heat output is required into the room where the stove is to be installed.

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» Do I require an air vent to be fitted?

All combustion appliances need oxygen to enable the fuel to burn safely and efficiently. Approved Document J of the Building Regulations for England & Wales specify the permanently open air supply that must be provided for the different types of fuel burning appliance.

Subject to the "air tightness" of the building an air vent is not generally needed for a wood or multi-fuel burning closed stove that has a rated output of 5kW or less. If the stove has an output greater than this a suitable air vent giving at least 550mm2 for each kW above 5kW needs to be provided. The 2010 edition of Approved Document J specifies additional air supply requirements if the building is built to the higher standards for air tightness. More details are given in the Ventilation - Air supply to stoves in the Regulations section.

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» What information is useful to bring along to the showroom?

It is helpful to bring as much information as possible such as: The rough size of the room you are thinking of installing the stove into; dimensions of the existing fireplace if you have one (height x width x depth); A digital photo of the fireplace and chimney is also useful even if taken on your mobile phone. If the chimney is old and may need lining you could download the Chimney relining form, complete the details and bring it with you.

If you would like a chimney for a new build, extension or barn conversion then the drawings including the plans and elevations with dimensions will be helpful.

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» How often do I need to sweep my chimney?

If burning dry seasoned or kiln dried wood you should sweep your chimney at least once a year and twice a year if burning solid mineral fuel (anthracite etc). Ideally the chimney should be swept before, during and after the heating season. Sweeping the flue keeps the chimney clear, to ensure the appliance operates efficiently and safely. Removing any tar like deposits will reduce the risk of a chimney fire. If wet wood has been burnt it is advisable to sweep the chimney more often to remove these deposits. Always check that the sweep is qualified and leaves a sweeping certificate, and beware of any sweep who does not use a proper bristle brush suited to the size of the flue.

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» Can I have a Wooden Beam or surround - distance to combustible materials?

The Building Regulations specify minimum clearances between flue pipes and combustible material such as beams. This is necessary to prevent burning the beam, see the Flue pipe and stove clearances from combustible materials guidance in the Regulations section.

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» What are smoke control areas and a DEFRA exempt appliance?

See the Smoke control areas explanation in the Regulations section.

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