Conservatory Building Regulations: When You're Exempt and When You Need Approval
Updated: 5 days ago
You are planning a new conservatory or changing the one you have, and you keep hearing "exempt", "Building Control" and "permitted development" as if they mean the same thing. They don't. Whether you need approval comes down to a short list of conditions, and a few common changes, like a solid roof or opening the room up to the house, take you outside them. Here is how conservatory building regulations work in England, from a team that replaces conservatory roofs every week.
Do you need building regs for a conservatory?
Usually not, if it meets the exemption rules. A new conservatory is normally exempt from Building Regulations when it is single storey, at ground level, under 30 square metres, separated from the house by external-quality walls, doors or windows, and heated independently. Glazing and fixed electrics must still comply.
The exemption only lasts as long as the conservatory keeps meeting those conditions. Swap the roof for a solid one, take out the doors to the house or plumb the room into your central heating, and you will usually need Building Regulations approval.
The conservatory building regulations exemption
Be built at ground level and be single storey
Be less than 30 square metres in floor area
Be separated from the house by external-quality walls, doors or windows
Have independent heating, with its own temperature and on/off controls
Have glazing and fixed electrics that meet the relevant Building Regulations
That last point catches people out. Even an exempt conservatory has to use safety glass in the right places, and any fixed electrical work has to meet the regulations. Exempt means you do not need to make an application. It does not mean anything goes.
When a conservatory needs Building Regulations approval
If any one of the exemption conditions is not met, the conservatory needs approval. According to LABC's guidance for homeowners, the most common triggers are:
It is over 30 square metres. A conservatory that size is treated as an extension.
It is open plan with the house. You will need to show the room is as energy efficient as the rest of your home.
It is heated from your central heating. Exempt conservatories must have independent heating.
It has plumbing. A sink, washing machine or toilet means an application is needed.
There is a new opening into the house. This needs approval even if the conservatory itself is exempt.
Heating: the easiest way to lose the exemption
Running a radiator off your boiler feels like a small job, but it is enough to end the exemption. LABC's guidance is that an exempt conservatory cannot be heated through your central heating system. A plug-in heater, or a separate system with its own controls, keeps you within the rules.
Opening the conservatory up to the house
The doors between the house and conservatory are what keep it "thermally separated". Take them out and the room is no longer separated from the house, so the exemption goes. Making a new opening, or widening an existing one, also needs Building Control approval in its own right, because it affects the structure of the house wall.
Building regs for a conservatory roof
If you are replacing a glass or polycarbonate roof with a solid one, you need Building Regulations approval. LABC is clear that switching a translucent conservatory roof to a solid roof needs an application, because the change has to be approved.
Replacing a glazed roof with another glazed roof is a different matter. Like-for-like translucent replacements do not change how the conservatory performs, so they do not affect the exemption in the same way.
This is the question we get asked most, because most of our work is conservatory roof replacement. We fit insulated solid roof systems from Warmer Room, a UK manufacturer, which turn a room that bakes in summer and freezes in winter into one you can use all year. The trade-off is that the room now needs sign-off.
What Building Control checks on a solid roof
The inspector will want to see that the new roof and the structure holding it up comply with the regulations, and that the rest of the conservatory is no worse than before. In practice that usually means:
Structure. Whether the existing frames and base can carry the new roof, or need extra support.
Insulation. The new roof has to meet current thermal standards.
Weatherproofing. How the roof meets the house wall, and how rainwater is taken away.
Once the work is signed off, you get a completion certificate. Keep it with your house paperwork, because it is your proof the job was done properly.
Building regulations vs planning permission
These are two separate systems, and being exempt from one does not mean you are exempt from the other.
Planning permission covers what you can build: the size, height, position and appearance. Many conservatories fall under permitted development, so no application is needed, but listed buildings, conservation areas and National Parks have tighter rules.
Building Regulations cover how it is built: structure, insulation, glazing, electrics and fire safety. A conservatory can be exempt from Building Regulations and still need planning permission, or the other way round, so check both before you commit to a design.
When your conservatory becomes an extension
If you want a room that is fully open to the house, heated from your central heating and comfortable every day of the year, you are describing an extension, and Building Regulations will apply either way. At that point it is often better to replace your conservatory with a timber frame extension built to extension standards from the start, rather than upgrading an old structure piece by piece. A new extension gets the same insulation and structure as the rest of the house, with Building Regulations approval built into the job from day one.
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