Do the Welsh rules allow an outdoor heat pump without a planning application?
In Wales the outdoor unit must stay within 1.5 m³ on a house and 1 m³ on a block of flats (Class G, checked 25 Sep 2026). The pump still has to satisfy the noise method the Order names.
computed
The Town and Country Planning (General Permitted Development) Order 1995 (SI 1995/418), Schedule 2, Part 40, Class G, as amended by The Town and Country Planning (General Permitted
Instrument checked 25 Sep 2026. Version 1.0.0.
| Point | Clause | Quote | Source | Version | Checked | In plain words | Input |
|---|---|---|---|---|---|---|---|
| WAL-01 | Class G, permitted development | The installation, alteration or replacement of an air source heat pump—(a) on a dwellinghouse; or (b) within the curtilage of a dwellinghouse, including on a building within that curtilage. | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | This proposal is not covered by this permitted-development class; a planning application may be needed. | Is the building a house, or a building that is wholly flats? |
| WAL-02 | G.1, as amended WSI 2026/79 art. 4(2) | Development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Compliance with the MCS 020a noise limit is required for this to be permitted development — see the noise check. | What is the noise result at 1 m outside the neighbour's nearest habitable-room window? |
| WAL-03 | G.2(a), as substituted WSI 2026/79 art. 4(3)(a) | in the case of the installation of an air source heat pump, it would result in the presence of—(i) more than one air source heat pump on, or within the curtilage of—(aa) a dwellinghouse which is not a detached dwellinghouse; (bb) a block of flats | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Too many air source heat pumps already on this building/curtilage for Class G (limit: 1, or 2 on a detached house). | How many outdoor units will the building have once this one is installed?; Is the house detached?; Is the building a house, or a building that is wholly flats? |
| WAL-03-WIND | G.2(b) (unamended by WSI 2026/79) | in the case of the installation of an air source heat pump, a stand alone wind turbine is installed within the curtilage of the dwellinghouse | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | A stand-alone wind turbine already in this curtilage blocks Class G for an air source heat pump. | Is there a stand-alone wind turbine in the garden? |
| WAL-04 | G.2(c), as substituted WSI 2026/79 art. 4(3)(b) | the volume of the air source heat pump's outdoor compressor unit (including any housing) would—(i) … a dwellinghouse, exceed 1.5 cubic metres; (ii) … a block of flats, exceed 1 cubic metre | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | The outdoor unit's volume exceeds the Class G limit for your building type in Wales (1.5 m³ house / 1 m³ block of flats). | What is the outdoor unit volume in cubic metres, including the housing?; Is the building a house, or a building that is wholly flats? |
| WAL-05 | G.2(e) (unamended) | the air source heat pump would be installed on a pitched roof | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Class G does not cover pitched-roof mounting. | Is the unit mounted on a roof? |
| WAL-06 | G.2(f) (unamended) | the air source heat pump would be installed on a flat roof where it would be sited within one metre of the external edge of that roof | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | A flat-roof unit within 1 m of the roof edge is not covered by Class G. | Is the unit mounted on a roof?; On a flat roof, how far is the unit from the external edge, in metres? |
| WAL-07 | G.2(h) (unamended) | the air source heat pump would be installed on a site designated as a scheduled monument | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Scheduled monuments are excluded from Class G. | Is the building a scheduled monument? |
| WAL-08 | G.2(g), as substituted WSI 2026/79 art. 4(3)(d) | the air source heat pump would be installed on a building or on land within the curtilage of the dwellinghouse or the block of flats if the dwellinghouse or the block of flats is a listed building | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | This cannot be checked reliably against the index — please check your address directly in Cadw's listed buildings register. | Is the building listed? A postcode search cannot clear this. |
| WAL-10 | G.2(i), as substituted WSI 2026/79 art. 4(3)(e) | in the case of land within a conservation area, the air source heat pump—(i) would be installed on a wall or a roof which fronts a highway; (ii) would be installed so that it is nearer to any highway which bounds the curtilage than the part of the dwellinghouse or block of flats which is nearest to that highway | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Conservation area: this wall-to-highway condition needs checking against your specific address. | Is this exact address inside a conservation area?; Does the wall the unit would sit on face a highway?; Does the roof face a highway?; Would the unit sit nearer the highway than the building does? |
| WAL-11 | G.2(j), inserted WSI 2026/79 art. 4(3)(f) | in the case of land, other than land within a conservation area, the air source heat pump would be installed on a wall of a dwellinghouse or block of flats if—(i) that wall fronts a highway, and (ii) … above the level of the ground floor storey | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | A highway-facing wall above ground-floor level is not covered by Class G outside a conservation area. | Does the wall the unit would sit on face a highway?; Is the unit above the ground floor? |
| WAL-09 | G.3(a), as substituted WSI 2026/79 art. 4(4) | the air source heat pump must not be solely used for the purpose of cooling | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Class G covers reversible air source heat pumps, not appliances used solely for cooling; this proposal is not covered by this permitted-development class — a planning application may be needed. | Will the pump be used only for cooling, or for heating as well? |
| WAL-DEF-DWELLINGHOUSE | paragraph J (interpretation), as substituted WSI 2026/79 art. 6(a) | “dwellinghouse” does not include a building containing one or more flats, or a flat contained within such a building | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Enter: Is the building a house, or a building that is wholly flats?. | Is the building a house, or a building that is wholly flats? |
| WAL-DEF-BLOCK-OF-FLATS | paragraph J (interpretation), inserted WSI 2026/79 art. 6(c) | “block of flats” means a building which consists wholly of flats | www.legislation.gov.uk/uksi/1995/418/schedule/2 | 1.0.0 | 25 Sep 2026 | Enter: Is the building a house, or a building that is wholly flats?. | Is the building a house, or a building that is wholly flats? |
| WAL-A4 | article 4(1), 'Directions restricting permitted development' | they may give a direction under this paragraph that the permission granted by article 3 shall not apply to—(a) all or any development of the Part, Class or paragraph in question in an area specified in the direction; or (b) any particular development, falling within that Part, Class or paragraph, which is specified in the direction | www.legislation.gov.uk/uksi/1995/418/article/4 | 1.0.0 | 25 Sep 2026 | An Article 4 direction applies here — the exact wording of the specific direction needs checking (it may or may not cover air source heat pumps). | Is there an Article 4 direction on this address?; Does that direction name this permitted-development class? |
| WAL-DATASET | n/a — DataMapWales/Cadw coverage gap | No statutory sentence is stored for this row. It records a gap in the geographic file, and a missing row is not a clearance. | — | 1.0.0 | 25 Sep 2026 | Enter: Is this authority covered by the planning dataset that was consulted?. | Is this authority covered by the planning dataset that was consulted? |
| mcs020a_1_1 | §1.2 | the permitted development noise limit of 37 dB LAeq,5mins (at the assessment positions ignoring the effect of the façade) | mcscertified.com/wp-content/uploads/2025/07/MCS- | 1.0.0 | 25 Sep 2026 | The noise limit in this method is 37.0 dB(A). | Sound power of the outdoor unit, distance to the neighbour’s window, and directivity Q. |
Next pages
The Town and Country Planning (General Permitted Development) Order 1995 (SI 1995/418), Schedule 2, Part 40, Class G, as amended by The Town and Country Planning (General Permitted Development) (Amendment) (Wales) Order 2026 (WSI 2026/79), · 25 Sep 2026 · n=17 · Each row is a point in docs/decision-contract.yaml. The engine that scores them is scripts/contract_engine.py. · updated 25 Sep 2026 · version 1.0.0 · CSV of the values on this page
Source detail
https://www.legislation.gov.uk/uksi/1995/418/schedule/2