UK Building Regulations Part J — Log Burner Installation Reference

The 5 Part J requirements

Hearth (J4) — dimensions and thickness

• Minimum freestanding area: 840×840mm
• Front projection: ≥300mm beyond the stove door (catches falling embers during refuelling). Reducible to 225mm for certain closed appliances; mandatory 300mm if the stove is designed to operate with the doors open
• Side and rear projection: ≥150mm beyond the stove body
• Superimposed hearth thickness: ≥12mm — permitted only if the stove is certified to keep hearth surface temperature below 100°C
• Constructional hearth thickness: ≥250mm solid masonry, or 125mm masonry over a 50mm ventilated air gap — required if the stove heats hearth above 100°C or hearth is untested
• Fireplace recess install: hearth projects ≥500mm into the room from the front of the chimney breast and extends ≥150mm on either side of the recess opening

See our hearth cost guide for material choices and pricing.

Flue and chimney (J2) — height and clearance

• Minimum total flue height: 4.5m from top of the stove
• Within 600mm horizontal of the roof ridge: flue outlet ≥600mm above the ridge
• Elsewhere on a pitched roof: outlet ≥2,300mm horizontally from the nearest weathered surface AND ≥1,000mm above the intersection (or as high as the ridge)
• Near rooflights or openings: ≥1,000mm above the opening within 3m horizontal distance
• Flue size: not smaller than the appliance outlet — typically 125mm/5" or 150mm/6" for solid fuel stoves under 20kW

For no-chimney installs (twin-wall flue), see our no-chimney install guide.

Distance to combustibles (J4)

• Single-skin flue pipe: ≥3× pipe diameter from any combustible element. A 150mm (6") pipe needs ≥450mm clearance
• Twin-wall flue: per manufacturer specification (typically 50–60mm)
• General stove clearance where no manufacturer data exists: ≥150mm rear/sides, ≥300mm front to combustibles
• Through masonry chimney: ≥200mm between flue surface and any combustible structural element (with minor exceptions for small fixings)

Air supply (J1)

• Pre-2008 homes, stoves ≤5kW: usually no dedicated vent required
• Pre-2008 homes, stoves >5kW: permanent vent providing 550mm² per kW above the 5kW threshold
• Post-2008 (airtight) homes: vent likely required regardless of output. Very airtight builds (air permeability ≤5 m³/h.m²) require 850mm² per kW from 5kW upwards
• Room-sealed alternative: a stove with direct external air supply doesn't need a room vent — recommended for new airtight builds, conservatories, and media wall installs

CO alarm (J3)

• Mandatory in any room with a fixed solid fuel appliance
• Certification: BS EN 50291 (current revision 50291-1:2018)
• Position: 1–3m horizontal from the stove, ≥300mm from any wall if ceiling-mounted, mounted on the ceiling or high on the wall (≥150mm below ceiling)
• 10-year sealed lithium battery models are the UK standard — no annual battery changes required

See our CO alarm buyer's guide for top picks and positioning details.

Notice plate (J5)

Approved Document J Requirement J5 mandates a durable notice plate near the appliance or meter showing:

• Stove make, model, and date of installation
• Flue type and dimensions (size, material)
• Chimney designation (if applicable)
• Maximum permitted fuel type
• Notes on any installation specifics future owners need

Common failure: missing or absent notice plate. Required for certification — if your install doesn't have one, the installer must fit it before issuing the HETAS certificate.

Scotland, Wales, Northern Ireland

• Scotland: Building Standards Technical Handbook Section 3 (Environment) covers combustion appliances. Different framework but broadly equivalent technical content
• Wales: follows Approved Document J similar to England
• Northern Ireland: NI Building Regulations Part L (separate from England's Part L which covers energy)

Where to read Part J

The official document is Approved Document J 2010 (with 2013 and 2022 amendments), published on gov.uk. Direct PDF link (large file): ADJ_2022.pdf →

For most homeowners the relevant sections are Section 2 (solid fuel installation requirements) and Appendix E (commissioning and notification).

Part J for complex install scenarios

Standard installs (existing chimney, freestanding stove in a standard recess) hit the core requirements above. Some scenarios require additional Part J interpretation — typically for hearth dimensions, clearance to combustibles, and party-wall or structural considerations:

• Double-sided / through-wall stoves — hearth and clearance on both elevations, structural detailing for the opening. Double-sided install cost →
• Conservatory installs — twin-wall flue routing through uPVC/polycarbonate/glass roofing, room-sealed air supply for airtight builds. Conservatory install cost →
• Flat / leasehold installs — Party Wall Act 1996 notifications, shared chimney compliance, lease consent. Flat install cost →
• Back-boiler stoves — Part J alongside plumbing and water-side safety controls. Back-boiler install cost →
• No-chimney (twin-wall flue) installs — flue height, fire-stopping at floor and roof penetrations, weather flashing. No-chimney install cost →

Frequently asked questions