Permitted development limits for rooflights
150mm above the roof plane, not above the ridge, and none of it applies to flats.
Part of our Conservation Rooflight Installation guide
Permitted development allows certain work without a planning application. For rooflights the conditions are specific.
The main conditions
No more than 150mm above the plane of the existing roof slope. The one people know.
Not higher than the highest part of the roof, so nothing projecting above the ridge.
On a side elevation, any window must be obscure glazed and non-opening below 1.7m above floor level.
Where it does not apply at all
Flats and maisonettes. Permitted development rights for this work do not exist.
Listed buildings. Listed building consent is required regardless.
Where an Article 4 direction applies, which may remove rights for the elevations covered.
Where rights have been removed by planning condition, common on newer estates.
Where rights have been used up by previous extensions.
Conservation areas
Rights still exist but are narrower. As a working rule, a slope facing a highway usually needs permission; a rear slope often does not.
Roof lanterns
A pitched glazed structure on a kerb is by definition taller than 150mm. On a rear extension this is normally assessed against the extension’s own roof and lanterns are routinely fitted; on a main roof slope it is a real constraint.
Building Regulations are separate
A job can need planning permission, Building Regulations approval, both or neither. A new opening is notifiable regardless of the planning position.
Checking
We check the designation and any Article 4 before quoting, because it changes the process and sometimes the product.
The three conditions
On an unlisted house outside any Article 4 direction, a rooflight is permitted development provided all three of these are met.
It projects no more than 150mm beyond the plane of the roof slope. Measured from the existing roof surface to the highest point of the new unit. This is the condition that matters most and it is why low profile units exist. A bulky dome standing well proud of the tiles fails it.
It is no higher than the highest part of the existing roof. In practice, nothing above the ridge.
On a side elevation facing a boundary, the glazing must be obscure, and any opening part must be either non opening below 1.7 metres from the floor of the room, or restricted so it cannot open below that height.
Meet those and no application is needed.
What removes the rights entirely
A listing. Consent is required for any rooflight on a listed building, on any slope, whether or not it can be seen. No exceptions and no thresholds.
An Article 4 direction. Common in conservation areas, frequently applying to elevations fronting a highway. A conservation area on its own does not remove the rights; a direction does.
Being a flat or maisonette. No permitted development rights at all, anywhere, ever.
A planning condition. Barn and agricultural conversions, and some new estates, are granted with permitted development rights removed by condition. Those run with the property regardless of who owns it now.
What the rights do not cover
Permitted development is a planning concept only. It says nothing about Building Regulations, which apply independently.
A new opening engages Part A for structure and Part L for energy efficiency. In a habitable loft room it engages Part B for means of escape. A replacement engages Part L as a controlled fitting. All of that is notifiable whatever the planning position, and it is the installer’s job to handle.
How to be sure
Two free enquiries. Search the national heritage list for your address. Then ask the local planning authority whether you are in a conservation area and whether an Article 4 direction applies.
Where there is genuine doubt, a lawful development certificate from the council confirms the position formally. It costs a fee and it is worth having on an unusual case, particularly if you expect to sell within a few years.
We do the first two checks as part of quoting.
Measuring the 150mm
From the existing roof surface to the highest point of the finished installation, including the flashing upstand where it stands proud. Not from the top of the rafters and not from the underside of the covering.
Manufacturers publish a section drawing showing exactly this dimension for each model, and it is the document to keep with your records in case the question ever arises.
Ask us
Tell us the address and we will check the listing, the conservation position and any Article 4 direction ourselves as part of quoting. It costs nothing and it takes a day rather than a week.
Where there is real doubt
A lawful development certificate from the council confirms the position formally. It costs a fee and it is worth having on an unusual case, particularly if you expect to sell within a few years or if a neighbour is likely to query the work. For a straightforward rear slope on an unlisted house outside any direction, it is not necessary.
One last point
Permitted development is a planning concept only. It says nothing about Building Regulations, which apply independently and are notifiable whatever the planning position. The two are frequently confused and they are entirely separate systems.
The conditions, in one place
Projection. The rooflight must not project more than 150mm above the existing roof plane, measured perpendicular to the slope at the highest point of the installation. That includes the flashing upstand and any kerb, not just the glazed part.
Height. No part may be higher than the highest part of the roof. A unit close to the ridge can fail this even where the projection is fine.
Side elevations. Where a rooflight serves a habitable room and faces a side elevation, obscure glazing and restricted opening conditions can apply.
Who does not have these rights
Flats and maisonettes have no permitted development rights for this at all.
Listed buildings need listed building consent regardless.
Conservation areas lose the rights on the principal elevation, and an Article 4 direction can remove them everywhere.
And rights may have been removed by a planning condition, which is common on newer estates, or used up by earlier extensions.
Confirming the position for a specific address takes one call to the council, and it is worth having in writing before ordering anything bespoke.
More on Conservation Rooflight Installation
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