There is no single legal distance from the boundary that applies to every air conditioner in England. Older chat about a one metre setback from the fence is not a rule to tape out on site. Place the outdoor unit so it meets the manufacturer's service and airflow clearances, so an engineer can work on it, and so the planning conditions that do exist are met: amenity, the MCS 020a noise route if you are using permitted development, highway and conservation limits, and the roof-edge rule where that applies. Survey the neighbour's windows. F-gas access matters as much as the fence.
A tape held against the garden fence
Class G, as the Planning Portal summarises it now, does not set one universal gap between the outdoor unit and the boundary fence. People still repeat an old one metre boundary habit. Relying on it will not make a noisy unit lawful, and ignoring a real condition because a forum said the metre rule had gone is just as weak. Read the current order or ask the local authority about this house.
Do not use a one metre boundary setback as a universal rule. Current Class G conditions do not set a single boundary setback of that kind. Check the current law for your site.
The manual's gaps, which are not neighbour law
What the manual does set are clearances: often a few hundred millimetres in front of the coil and space to remove covers, varying by model. Those exist so the unit can reject heat and be serviced. They are not a neighbour-law distance. Look them up for the exact outdoor model. Do not borrow another brand's diagram.
- No universal legal metre from the boundary.
- Follow the manual's clearances for that outdoor unit.
- Leave room for an engineer, not only for airflow.
- Bedroom windows matter more than the fence line.
The metre that belongs to a flat roof edge
If you are relying on permitted development in England, the unit has to meet the whole Class G list: MCS 020a, volume limits, not on a pitched roof, and on a flat roof at least one metre from the roof edge. Legislation.gov.uk is that Class G text. That roof-edge metre is a roof rule, not a boundary-fence rule. Conservation areas restrict highway frontages. The unit must not be used solely for cooling. Listed curtilage is outside the right.
A second unit on a semi or terrace often needs an application because only the first installation is permitted development on a house that is not detached. Flats often still need permission. Article 4 directions and conditions on the estate can remove the rights. None of those tests is replaced by standing one metre off the fence.
A side passage blowing at a close timber fence
Further from a neighbour's bedroom window is kinder and usually sounds better, even when the fence itself is not the legal measure. A unit jammed in a side passage, blowing at a close timber fence, can be noisier than the same unit on a more open rear wall. Reflection and vibration are physical. Energy Saving Trust describes air-to-air heat pumps. It does not set a fence distance.
Manual clearances keep the machine alive. They do not settle noise or permitted development. You can put the unit right on the boundary only if planning, the lease and basic neighbour amenity also allow that spot. Survey it properly.
Stop if a tight box is how you fix the boundary
Do not solve the boundary by building a tight acoustic box. You will starve the coil, raise electricity use and shorten the equipment. Screens, if you use them, have to preserve the manual's air paths. The surveyor should sketch that, not a salesperson. On the survey, ask them to mark the outdoor unit against the boundary, the nearest habitable windows, the manual clearances, and whether they are relying on permitted development or an application. Include service access. A unit that cannot be reached will not be maintained, GOV.UK F-gas ticket or not. Photos along the boundary and up to the neighbour's windows, from your side, are the record. You want the position that meets the manual and the actual planning conditions.
Frequently asked questions
Is there a legal one metre rule from the boundary?
Do not use one as a universal rule. Current Class G conditions, as summarised on the Planning Portal, do not set a single boundary setback of that kind. Check the current law for your site. Do follow the manufacturer's clearances and any planning condition that is actually imposed.
What is the one metre figure that does appear?
On a flat roof, Class G requires the air source heat pump to be at least one metre from the external edge of that roof. That is a roof-edge condition, not a distance from the garden fence.
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.