Orangery and conservatory drawings for Hillingdon homes — checked against the Class A rear limits and the 30m² building-regulations exemption, drawn to Hillingdon Council's guidance and revised free until your decision.
Hillingdon Council granted 84% of the householder planning decisions it made in its latest published year — 3 points below the 87% England-wide householder average. A large slice of the borough sits in Green Belt to the west, where extensions face the openness test rather than ordinary householder policy, which is where a policy-literate drawing pack earns its keep. Its dominant Edwardian (1901–1910), interwar (1918–1939) and postwar (1945–1970) housing stock sets the design brief on most streets.
Class A and Class B set the thresholds — a rear dormer to 40m³ on a terrace or 50m³ on a semi or detached, and a single-storey rear extension to 3m on a terrace or 4m on a detached house — beyond which Hillingdon Council needs a full application. Hillingdon carries at least one Article 4 direction, and conservation areas including Old Uxbridge, Harefield Village and Ickenham Village remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Hillingdon is determined against an 8-week statutory target.
Uxbridge (the town centre with its Old Uxbridge conservation area and Edwardian terraces), Ruislip (Metro-land semis around the Ruislip Village conservation area), Ickenham (a village green surrounded by interwar suburban housing), Harefield (a rural Green Belt village of cottages and detached homes), Northwood (affluent detached and semi-detached houses on leafy plots) and Hayes (mixed interwar and postwar estates near the former industrial belt) — these are the Hillingdon pockets our drawings cover most. Heritage designations here include Old Uxbridge, Harefield Village, Ickenham Village, Ruislip Village and Eastcote. Hillingdon Council weighs each proposal against Hillingdon Local Plan and the HDAS: Residential Extensions SPD, where the design guidance polices the spacing and building line of Metro-land semis so paired houses keep their rhythm. On roofs the borough is hipped roofs on the 1930s semis and gabled roofs on the older village cottages, over interwar Metro-land semi-detached houses, Edwardian terraces around Uxbridge and West Drayton and detached houses and cottages in the rural western villages.
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 Hillingdon Local Plan and the HDAS: Residential Extensions SPD. Hillingdon is largely interwar Metro-land semi-detached houses, Edwardian terraces around Uxbridge and West Drayton and detached houses and cottages in the rural western villages, 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 Old Uxbridge and Harefield Village, rear glazing is assessed on visibility from the street and on the effect on the rear elevation's character. Ruislip Village and the Harefield and Ickenham conservation areas carry tight controls, and Article 4 directions on some of these older village streets strip out the permitted-development rights suburban owners otherwise assume.
Many conservatories are permitted development. You will need an application to Hillingdon 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 Hillingdon Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Hillingdon grants a fair share of householder applications, with Green Belt openness in the western villages and roof and spacing changes to interwar semis the recurring pinch points. 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 Uxbridge, Ruislip and Ickenham, 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 metro-land 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.
A large slice of the borough sits in Green Belt to the west, where extensions face the openness test rather than ordinary householder policy. 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 Hillingdon. A few of the areas where they come up most often:
Orangery and conservatory drawings for Uxbridge — the town centre with its Old Uxbridge conservation area and Edwardian terraces — checked against the Class A limits and drawn to Hillingdon Council's guidance.
Orangery and conservatory drawings for Ruislip — Metro-land semis around the Ruislip Village conservation area — checked against the Class A limits and drawn to Hillingdon Council's guidance.
Orangery and conservatory drawings for Ickenham — a village green surrounded by interwar suburban housing — checked against the Class A limits and drawn to Hillingdon Council's guidance.
Orangery and conservatory drawings for Harefield — a rural Green Belt village of cottages and detached homes — checked against the Class A limits and drawn to Hillingdon Council's guidance.
Orangery and conservatory drawings for Northwood — affluent detached and semi-detached houses on leafy plots — checked against the Class A limits and drawn to Hillingdon Council's guidance.
Orangery and conservatory drawings for Hayes — mixed interwar and postwar estates near the former industrial belt — checked against the Class A limits and drawn to Hillingdon 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 Hillingdon postcode and house type. We confirm the Class A limits that apply, check designation status, and score your odds against live Hillingdon 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 Hillingdon 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 Hillingdon you will need an application to Hillingdon Council beyond those limits, and on designated land such as Old Uxbridge and Harefield Village.
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 Hillingdon address specifically. Hillingdon Council is the decision-maker.
For planning, none — both are rear extensions assessed against the same Class A limits by Hillingdon 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 Hillingdon address specifically. Hillingdon 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 Hillingdon address specifically. Hillingdon 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 Hillingdon Council's planning decision. We flag it at design stage so the notice period does not delay the start on site.
We quote each Hillingdon 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 Hillingdon Council approves. Call 020 7864 7245 to start.
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