The short answer for Rayners Lane
Planning authority
London Borough of Harrow
Postcode district
HA2
Households in terraces
1,426 of 2,908
Conservation area
One, on Alexandra Avenue
Not sure you are in Rayners Lane? Check your area
Yes, we cover Rayners Lane. It is a suburb of terraces: at the 2021 Census 1,426 of the 2,908 households in Rayners Lane ward lived in a terraced house, against 15,136 of 89,642 across Harrow. Harrow's own study describes the 1930s Nash estate as rows of three, four and six houses, with narrow gaps at the ends of the rows and a service alley behind every house. That points the outdoor unit to the back wall, and national permitted development covers one outdoor unit on a terraced house, so ask about a second room before you plan it. The only designation is a small conservation area on part of Alexandra Avenue by the station, with no Article 4 direction. Planning here is Harrow's, though the ward's south western edge runs along the Hillingdon boundary.
Wall mounted systems start from £1,995 fully installed, and the price does not change with the postcode.
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- We come and do a free survey at your address.
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The survey is free, and nothing is booked before you have the price in writing.
What the housing actually is
Households by accommodation type at the 2021 Census, for Rayners Lane ward and for the whole of Harrow. Terraced is the largest single group in the ward, and in Harrow it is well behind semi detached and flats.
| Area | Households | Detached | Semi-detached | Terraced | Purpose built flats |
|---|---|---|---|---|---|
| Rayners Lane ward | 2,908 | 102 | 910 | 1,426 | 327 |
| Harrow, whole borough | 89,642 | 10,174 | 33,281 | 15,136 | 23,528 |
ONS Census 2021, table TS044, accommodation type by household, as at 21 March 2021, on the 2022 ward boundaries. Only the categories ONS publishes are shown; the remaining households are in converted or shared houses, other converted buildings, commercial buildings (42 in the ward, such as over a shop) or temporary structures. The Nash estate also runs into neighbouring wards, so these figures describe the ward and not the estate.
The Nash estate, and the lane behind the house
Harrow's conservation area appraisal says T F Nash and Company took most of the land south of the station and concentrated on mass producing cheaper housing, and that most of it was finished by 1935. Harrow's 2011 character study describes the result as mainly terraced houses in rows of three, four and six, with a few smaller pockets of semi detached ones.
The same study notes narrow spaces at the sides of end terraces, though access roads break up the frontage, and says every house is served by a rear service alley. It also records that many front gardens have been lost to forecourt parking.
So the front of a house is bays and parked cars, and the back wall is the usual place for the outdoor unit. A front room in a mid terrace has no side to run pipework along, so the route to the back matters. The starting price includes three metres of pipework, and any run beyond that is a priced line on the quote.
One conservation area, and it is one road
Harrow dates the Rayners Lane conservation area to 2003 and adopted its appraisal in December 2009. Its schedule lists properties on Alexandra Avenue only, numbers 411 to 475 and 420 to 472, plus the Underground station and the former cinema. Harrow's table gives it no Article 4 direction.
What it protects is shops with flats above, round the station. The former Ace Cinema, which Harrow's schedule also calls the Grosvenor, is Grade II star on Historic England's list, and the station is Grade II. A third listing, the Rayners public house on Village Way East, is also Grade II and is not in the conservation area schedule.
Harrow's appraisal lists air conditioning units among the pressures on the area, saying they can be very visually obtrusive where poorly sited and visible from the street. Its answer is that they be as concealed as possible, which usually means installation where they are not visible from the street.
What applies to you
You own a terraced house
That is most of the suburb. Permitted development covers one outdoor heat pump on a terraced house, and a second outdoor unit is where an application starts to be needed, so decide your rooms before the survey. The unit goes on the back wall, and we position it with your neighbour's windows in mind.
You own a semi detached house
910 households in the ward. The same one unit limit applies, because only a detached house gets two. A semi usually has a side to use as well as the back, and since the one metre boundary rule went on 29 May 2025 a narrow side is no longer ruled out on that ground.
You live in a flat
327 households in the ward are in purpose built blocks, and 42 more live in commercial buildings such as over a shop. The freeholder's written consent comes first. Harrow's appraisal says alterations to flats in the conservation area require planning permission, and its planning team can say whether your flat has permitted development rights.
Your address is in the conservation area or listed
In a conservation area the unit cannot go on a wall or roof that fronts a highway, so it goes to the rear, out of sight of the street, which is what Harrow asks for. A listed building has no permitted development at all and needs a conversation with Harrow's conservation team first.
You are a business
The shops and restaurants round the station are non domestic, outside the heat pump permitted development rules, so an application to Harrow is likely. Our commercial page covers how we handle those, and we will give you the unit dimensions and position for the form.
Which council, and the Hillingdon edge
The station, the former cinema and the postcodes sampled across the ward all fall in Harrow on the Office for National Statistics boundaries, and the ward's postcodes are in HA2. The ward's south western edge is different. There it runs along the Hillingdon boundary, and Harrow's study notes Hillingdon open space at the end of Yeading Avenue.
A house just across that line is Hillingdon's to decide, and its postcode can change with it. Harrow's conservation team takes questions on 020 8736 6101, and its conservation area page lets you check a postcode. We establish which council your address is in before we quote.
Your planning authority is London Borough of Harrow
They decide any application for your address, and they publish the conservation area maps you would need to check it. We do not submit applications on your behalf, but we will tell you at the survey if one is likely and give you the unit dimensions and position to put on the form.
London Borough of Harrow conservation areasWhat we would fit in Rayners Lane
Every price is fully installed and includes the unit, the installation, the electrical work and VAT.
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Instant estimate
Mid terrace, end of terrace or semi?
Tell us the room and the type of house and we will say where the outdoor unit is likely to go. Size your room in about a minute and we will give you a figure.