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What installing a pellet stove or boiler actually involves

A proper installation covers the flue route, hearth clearances, combustion air, where the appliance sits, and the paperwork that proves it meets Building Regulations. This page sets out what a competent HETAS-registered installer's survey should cover, but it does not replace that installer's own assessment of your house.

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Survey stages

What an installer should check on survey

These are the points a competent installer works through before quoting the job, roughly in the order they come up.

  • Flue and chimney condition

    An installer establishes whether an existing chimney can take a flue liner (the inner sleeve fitted inside a chimney or flue run) or whether a new flue run is needed, and checks that the outlet reaches the height required above the roof and any nearby openings.

  • Hearth and clearance distances

    The appliance's stated clearance from combustible materials such as skirting boards and furniture has to be checked against the existing hearth, which may need replacing if it falls short.

  • Ventilation into the room

    The room needs a permanent air supply sized to the appliance's output, and an installer should confirm whether that means fitting a new vent.

  • Where the appliance can sit

    Siting has to allow for hopper refilling, ash removal and clearance from doors, windows and other fixed openings.

  • Building Regulations notification

    Work on a solid fuel appliance falls under Approved Document J of the Building Regulations, and gets notified either through a HETAS installer's self-certification or a separate application to local authority building control.

  • HETAS registration of the installer

    An installer's HETAS (Heating Equipment Testing and Approval Scheme) status should be checked on the HETAS online register, since self-certification only holds if the registration is current.

This sequence describes what a survey covers, and does not replace a competent installer's own assessment of your property. A shared flue, a listed building, or a room without an existing air vent can each need extra steps beyond this list.

Questions worth asking before you commission the work

A competent installer will answer these questions without hesitation, because the answers describe work they do routinely. Hesitation, vagueness or irritation at being asked is itself an answer worth noting.

What to ask before any work starts

  • Is the appliance covered by your HETAS registration? HETAS (the Heating Equipment Testing and Approval Scheme) registration is specific to appliance types and fuels, so an installer registered for gas is not automatically registered for biomass. Ask for the registration number and check it yourself on the HETAS online register.
  • What size flue liner does this appliance need, and why? The flue liner is the inner sleeve fitted inside a chimney or flue run to match the appliance's exhaust requirements. A proper answer names a diameter and a reason (appliance output, run length, number of bends).
  • What clearance distances apply to combustible materials? Hearth size and clearance to timber, plasterboard or furniture are set by the appliance manufacturer's instructions and checked against Building Regulations. An installer should be able to point to the manufacturer's data sheet.
  • How will the room be ventilated? Combustion needs a supply of air, and above certain appliance output thresholds a permanent vent is required regardless of how airtight the room already feels. Ask what the appliance's stated output is and whether that triggers a ventilation requirement.
  • Will this be self-certified or notified to building control? A HETAS-registered installer can usually self-certify the work under a competent persons scheme, which is faster and cheaper than a local authority building control application, but not every installer or every job qualifies. Ask which route applies and why, and ask for the paperwork that proves it happened.
  • What does the quote actually include? Flue liner, hearth, ventilation works, commissioning and certification are separate cost items that can be missing from a headline figure. A written quote should itemise each one.

What the answers tell you

A clear, specific answer to each question is a reasonable sign that the survey has been done properly. A shrug, a verbal assurance with nothing written down, or a quote that omits certification are reasons to ask again before committing.

None of this replaces a competent registered installer's own assessment of your property, and this page does not constitute energy advice. Read the fuller sequence of installation requirements, from flue assessment through to certification, in What Installation Really Involves, and check any installer's current status directly on the HETAS register before agreeing to work.

Building Regulations and the two routes to compliance

Fitting a pellet stove or boiler counts as notifiable work under Building Regulations, because it usually means a new flue penetrating a wall or roof, a change to the room's ventilation, and an appliance burning fuel inside an occupied building. The regulation that applies is Approved Document J, which covers combustion appliances and fuel storage. You do not choose whether the work is notifiable. You choose how it gets notified.

Two routes to compliance

There are two ways to satisfy Building Regulations for a solid fuel or biomass appliance, and they lead to the same legal outcome by different paths.

  • HETAS self-certification: a HETAS (Heating Equipment Testing and Approval Scheme) registered installer signs off the work themselves and notifies the local authority on your behalf. HETAS is a competent persons scheme recognised under Building Regulations for solid fuel and biomass appliances. You receive a certificate at the end, and no separate council inspection takes place.
  • Local authority building control notification: you or your installer notify the council before work starts, and a building control officer inspects the installation, usually after completion. This route applies if your installer is not HETAS-registered, or if you would rather have an independent inspection regardless.

Most homeowners use the HETAS route, because it avoids a separate council fee and a second site visit. It only works if the installer carrying out the work is actually registered for the class of appliance being fitted, which is not the same as being registered at all: registration can be scoped to stoves, boilers, or both.

What each route actually confirms

A HETAS certificate confirms that the specific installation, the flue run, the hearth, the clearances, the ventilation, meets the standard. A building control completion certificate confirms the same technical points through council inspection. Either document is what you produce if you sell the house, claim on insurance after a chimney fire, or need to show a mortgage lender that the heating system is compliant.

Checking before work starts

Ask which route the installer intends to use, and ask to see the HETAS registration number if that is the route. The number can be checked against the HETAS online register directly. If no certificate of either kind is offered at the end of the job, the work is not compliant regardless of how well the appliance runs.

This page does not replace an installer's own survey of your property, and building control requirements can vary by local authority. See Pellets: Quality, Storage and Delivery for what the fuel storage side of Approved Document J involves, or get in touch if you want to talk through what applies to your house.