Do Conservatories Fall Under Permitted Development? Building Regulations and Permitted Development for Conservatories Explained

The purpose of this blog post is to explain the building regulation requirements

and permitted development status of conservatories and conservatory replacements. If you're looking to enhance your home with a new conservatory, you've come to the right place! We construct bespoke home extensions for all homeowners. Read on to find out if conservatories fall under permitted development & learn more about building regulations for home extensions.

Are There Building Regulations For A New Conservatory?

Thankfully, a conservatory is an exempt building under Regulation 9(1) and Schedule 2 Class 7 of the Building Regulations (2010) as amended, and is, therefore, exempt from

building regulations.

However, there is no statutory definition of a conservatory, and some of the more

popular modern designs for a ‘conservatory would be more properly classified as an

extension which would, therefore, have to be compliant with building regulations.

Under the MHCLG Divisional Circular Letter ‘Conservatories and Porches’ (30 July

2013), a document which provides guidance on the interpretation of building

regulations for inspectors, a conservatory will normally qualify for an exemption if:

1. It is on the ground level

2. It must not exceed 30m 2 of internal floor area

3. It must be ‘substantially glazed’ – this is commonly interpreted in industry

practice to be around 75% of the roof as glass and around 50% of the walls.

4. Thermal separation is maintained between the house and the conservatory

(i.e. existing external doors remain in place).

5. The heating system is not extended.

If your conservatory or conservatory replacement does not comply with all the above

points it is most likely to be classified as an extension and not as a conservatory, and

therefore, will need to comply with full building regulations.

Most home extensions that we build at Allgood Construction require full building

regulations. However, we are more than happy to build conservatories for customers

that want them and you will find several examples of conservatories that we have

built for customers on this page.

Many older conservatories were originally built as exempt structures under building

regulations. However, when replacing a conservatory, particularly when installing a

solid roof system or removing the thermal separation (i.e. the external doors between

the conservatory and home) that exemption is lost.

In this situation, the structure is likely to be treated as a home extension and then

must comply with building regulations.

Do Conservatories Fall Under Permitted Development?

A conservatory will usually fall under Class A of your permitted development rights.

We have a deep dive available here and we would encourage you to read the

Government technical guidance documents available here.

The short version is that you will most likely be able to build up to 3 metres off the

back of your house if you are a semi-detached or terrace house, and 4 metres off the

back if you are a detached house. You will also be able to extend to the side 50% of

the width of the original house.

So long as your project complies with your permitted development rights, then you

will not require planning permission.

Can I Extend My Existing Conservatory Under Permitted Development?

Extending old conservatory bases to allow for a larger conservatory is a common

request from our customers, and there are a few things to consider when looking at

extending the base.

The first is the quality of the existing base. As conservatories are an exempt building

under building regulations, there are substantial variations in the quality of the base.

It is not uncommon to find older bases which lack sufficient depth to be structurally

sound, lack insulation and have no damp proof coursing. In such cases, our recommendation is to remove the base and start with a fresh, well-built foundation to

ensure maximum longevity for your project.

The second common issue is regulatory ambiguity, specifically under section 11.3 of

Approved Document L Conservation of Fuel and Power Volume 1: Dwellings, 2021

edition incorporating 2023 amendments.

This section states that where a thermal element is renovated and this constitutes a

‘major renovation’ (this is defined as where more than 25% of the surface area of the

external building envelope is renovated) then the whole of the thermal element must

be improved.

There are some building inspectors who will interpret this section as requiring that

the existing conservatory base will have to be improved as a result of extending the

base. However, other building inspectors will not view extending the base as

renovating the existing thermal element. This is a matter of ambiguity in the

regulation.

As a matter of routine, we will always engage with the building inspector on their

expectations to ensure that we have absolutely clarity on whether we will need to

alter the base or not.

Why Should You Replace Your Conservatory?

Older conservatories often suffer from poor thermal performance, condensation and

ventilation issues, and a dated appearance. Often, buyers treat them as a project to

be dealt with, rather than adding value to your home they can subtract it.

Simply swapping the roof system can introduce new issues. As a consequence of

older conservatories not being built under building regulations, there is a high

likelihood that the conservatory foundations is not going to be adequate for a

traditional brick extension. This would require either underpinning the foundations, or

removing the base and starting from scratch, both adding additional cost into your

jobs.

There are some exceptions that we do come across when we visit customers jobs,

especially in the case where conservatories were build at the same time as the

original house and therefore has the same foundations. However, this is not the case

for the majority of cases that we encounter.

Where we have foundations which are properly insulated, well-built and damp proof

coursing, we would usually use Ultraframe’s Hup! Extension System. We are

network installer for this system, and where a conservatory base is otherwise good

but cannot withstand the weight of a brick extension, we always recommend the

Hup! System.

Hup! Is precision engineered using Structural Insulated Panels (SIPs) to give you

proper wall construction, structural integrity designed for solid roof loads, and predictable compliance with building regulation requirements. Due to the lightweight

nature of Hup! We can usually use older conservatory bases to save cost, without

compromising of the quality of the extension.

There are additional advantages. For instance, because the thermal performance of

the Hup! System is superior to brick, they are thinner than a traditional extension wall

and usually provide between 10-15% greater internal space compared to a

traditional extension.

Disclaimer: These blog posts reflect the experience and opinion of our organisation

as primary contractors working in the construction sector. We are not Registered

Building Control Approvers, legal professionals, planning professionals or affiliated

with any Local Planning Authority. We will always recommend that our customer

seek guidance from their Local Planning Authority on all matters relating to planning

permission or building regulations and it is your responsibility to do so.