Orangery and conservatory drawings for Harrow homes — checked against the Class A rear limits and the 30m² building-regulations exemption, drawn to Harrow Council's guidance and revised free until your decision.
Harrow Council granted 83% of the householder planning decisions it made in its latest published year — 4 points below the 87% England-wide householder average. Hip-to-gable conversions dominate because so much of the stock is hipped 1930s semis — roof bulk and the pair's balance are the tests, which is where a policy-literate drawing pack earns its keep. Its dominant Edwardian (1901–1910) and interwar (1918–1939) housing stock sets the design brief on most streets.
The permitted-development ceilings are fixed: 40m³ of new roof volume for a terraced loft and 50m³ for a semi or detached house under Class B, plus a 3m single-storey rear extension on a terrace or 4m on a detached house under Class A. Harrow carries at least one Article 4 direction, and conservation areas including Harrow on the Hill, Pinner High Street and Pinner Village remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Harrow is determined against an 8-week statutory target.
Harrow on the Hill (historic hilltop conservation area), Pinner (the medieval High Street and Metroland semis), Stanmore (detached and semi-detached interwar houses), Wealdstone (Edwardian terraces near the town centre), Rayners Lane (classic Metroland semi-detached estates) and Kenton (1930s hipped-roof semis) — these are the Harrow pockets our drawings cover most. Heritage designations here include Harrow on the Hill, Pinner High Street, Pinner Village, Roxeth and Harrow Weald. Harrow Council weighs each proposal against Harrow Local Plan and the Residential Design Guide SPD, where the borough resists loss of the gaps between semis that define Metroland streets. On roofs the borough is hipped roofs on the 1930s semis and steeper gabled roofs in Pinner village, over interwar Metroland semi-detached houses, Edwardian terraces around the stations and detached homes on the hill.
The difference is not marketing. A conservatory is predominantly glazed — at least three quarters of the roof and half of the walls — which is what earns it the building-regulations exemption. An orangery has a solid masonry perimeter with a glazed lantern set into a flat roof, so it usually reads as a conventional extension for building control and has to meet Part L thermal standards, Part A structure and Part B fire like any other room.
Both are judged the same way for planning: as rear extensions, against the Class A depth, height and eaves limits, and against Harrow Local Plan and the Residential Design Guide SPD. Harrow is largely interwar Metroland semi-detached houses, Edwardian terraces around the stations and detached homes on the hill, and the design question is usually whether the glazing reads as a lightweight addition to that stock or as a bolted-on conservatory kit. On period houses, an orangery with a properly proportioned lantern almost always sits better than a full-height glazed box.
In conservation areas such as Harrow on the Hill and Pinner High Street, rear glazing is assessed on visibility from the street and on the effect on the rear elevation's character. Harrow on the Hill and the Pinner conservation areas carry tight controls, and several streets have Article 4 directions removing permitted-development rights.
Many conservatories are permitted development. You will need an application to Harrow Council where any of these apply:
We check the scheme against the Class A planning limits and against the building-regulations exemption at the same time, so you know before committing whether you are building an exempt conservatory or a fully regulated room.
Below is Harrow Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Harrow grants a fair share of householder applications, with hip-to-gable roof bulk on Metroland semis and the spacing between paired houses the recurring considerations. Glazed rear additions are judged on depth, eaves height and how the glazing meets the existing elevation.
Source: MHCLG planning application statistics (householder decisions, rolling year). Compare every borough on our London approval-rate league table.
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Across Harrow on the Hill, Pinner and Stanmore, the schemes that succeed keep the eaves below the neighbour's ground-floor cill line, set the glazing back from the boundary, and use a solid parapet or brick perimeter to tie the addition into the house. On interwar metroland semi-detached houses, a lantern set in a flat roof usually reads better than a pitched glazed roof, and it avoids the summer overheating that makes full conservatories unusable for months a year.
Hip-to-gable conversions dominate because so much of the stock is hipped 1930s semis — roof bulk and the pair's balance are the tests. The decision worth making early is whether to keep the separating doors. Keeping them preserves the building-regulations exemption but leaves you with a room that is not part of the house; removing them creates one continuous space but brings the whole addition inside Part L, which changes the glazing specification and usually the heating design too. We set out both versions before you commit.
We draw glazed rear additions across Harrow. A few of the areas where they come up most often:
Orangery and conservatory drawings for Harrow on the Hill — historic hilltop conservation area — checked against the Class A limits and drawn to Harrow Council's guidance.
Orangery and conservatory drawings for Pinner — the medieval High Street and Metroland semis — checked against the Class A limits and drawn to Harrow Council's guidance.
Orangery and conservatory drawings for Stanmore — detached and semi-detached interwar houses — checked against the Class A limits and drawn to Harrow Council's guidance.
Orangery and conservatory drawings for Wealdstone — Edwardian terraces near the town centre — checked against the Class A limits and drawn to Harrow Council's guidance.
Orangery and conservatory drawings for Rayners Lane — classic Metroland semi-detached estates — checked against the Class A limits and drawn to Harrow Council's guidance.
Orangery and conservatory drawings for Kenton — 1930s hipped-roof semis — checked against the Class A limits and drawn to Harrow Council's guidance.
The planning test is the same for both. The building-regulations test is not.
| Structure | Planning route | Building regulations | Practical effect |
|---|---|---|---|
| Conservatory under 30m², doors retained | Class A rear extension limits | Largely exempt | Cheaper build, unheated in winter |
| Conservatory, doors removed | Class A rear extension limits | Part L applies in full | Continuous space, higher spec glazing |
| Orangery with solid perimeter and lantern | Class A rear extension limits | Fully regulated | Usable year round, better on period houses |
| Any of the above beyond the depth limits | Full householder application | As above | 8-week determination |
| Any of the above on designated land | Full householder application | As above | Design and visibility assessed |
Planning limits from the GPDO 2015, Schedule 2, Part 1, Class A; exemption criteria from the Building Regulations 2010, Schedule 2, Class 7.
A fixed process covering both consents, because they pull in different directions.
Send us your Harrow postcode and house type. We confirm the Class A limits that apply, check designation status, and score your odds against live Harrow Council decisions.
We measure the rear elevation, eaves and ground levels, and the neighbouring boundary — the numbers that decide both the projection limit and the 2-metre eaves rule.
Chartered designers develop the orangery or conservatory to your brief, and we set out clearly whether it stays inside the building-regulations exemption or becomes a fully regulated room.
We submit the certificate or application, manage validation and officer queries, and revise free until Harrow Council decides.
Often not. A conservatory is treated as a rear extension, so it can be permitted development within the Class A limits — 3 metres of projection on a terrace or semi, 4 metres on a detached house, with eaves under 3 metres where it sits within 2 metres of a boundary. In Harrow you will need an application to Harrow Council beyond those limits, and on designated land such as Harrow on the Hill and Pinner High Street.
A conservatory is largely exempt if it is under 30 square metres, at ground level, separated from the house by external-quality doors, and has at least 75% of its roof and 50% of its walls glazed. Glazing, electrics and any drainage work still have to comply. Remove the separating doors and the exemption falls away — the space becomes part of the house and Part L thermal standards apply. This applies to your Harrow address specifically. Harrow Council is the decision-maker.
For planning, none — both are rear extensions assessed against the same Class A limits by Harrow Council. The difference is in building control: an orangery's solid perimeter and flat roof with a lantern usually means it fails the glazing test for exemption, so it is fully regulated. That is why an orangery costs more to build but is comfortable in January.
Usually yes at the rear, though permitted-development rights are narrower on designated land and an Article 4 direction can remove them entirely. The assessment turns on whether the addition is visible from the street and how it meets the original rear elevation. A restrained orangery in matching brick with a lantern is consistently easier to get through than a proprietary glazed conservatory. This applies to your Harrow address specifically. Harrow Council is the decision-maker.
A fully glazed roof will, unless it is specified for it. That is the practical reason most of our clients end up building an orangery instead: a solid insulated roof perimeter with a lantern gives daylight without the greenhouse effect, and keeps the space usable across the year. We raise it at design stage because it is much cheaper to solve on paper than after the build. This applies to your Harrow address specifically. Harrow Council is the decision-maker.
If you excavate foundations within 3 metres of a neighbouring structure and deeper than its foundations, or build on the boundary itself, the Party Wall etc. Act 1996 applies and notice must be served. That is separate from Harrow Council's planning decision. We flag it at design stage so the notice period does not delay the start on site.
We quote each Harrow orangery or conservatory individually, because the structure and the roof form change the work considerably, and send a fixed, no-obligation quote within one working day. It covers the full drawing pack with free revisions until Harrow Council approves. Call 020 7864 7245 to start.
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