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Get a quoteLoft conversion planning permission and building regulations
From permitted development to party wall agreements, here's what you need to know before converting your loft
Most loft conversions can be carried out without planning permission, but you'll still need to satisfy building regulations.
In this guide, we tell you how to work out whether you need planning permission or not, what building regulations to consider, how party wall agreements work, and any other permissions you may need in place before you start.
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Do you need planning permission for a loft conversion?
Most homes will come with an allowance for permitted development (PD), which means you can go ahead with your conversion without planning permission.
You shouldn't need planning permission for a loft conversion if your proposed conversion satisfies the following conditions:
- The total area of the additional space won't exceed 40 cubic metres for terraced houses or 50 cubic metres for detached or semi-detached houses (this allowance includes not only any extra space you create with this loft, but also any previous additions that have been made, such as an extension).
- The extension does not reach beyond the outermost part of the existing roof slope at the front of the house.
- The extension does not go higher than the highest part of the roof.
- Materials are similar in appearance to the existing house.
- There are no verandas, balconies or raised platforms.
- Side-facing windows are obscure-glazed (for example frosted or patterned to stop people seeing in).
- Side-facing window openings are 1.7m or more above the floor.
- Your house is not on designated land, namely national parks, areas of outstanding national beauty, the Broads, conservation areas and World Heritage sites.
- Roof extensions, other than hip-to-gable ones, are set back as far as practicable, at least 20cm from the original eaves.
- The roof enlargement does not overhang the outer face of the wall of the original house.
If you're unsure, or think you might need planning permission, an initial discussion with an architect or builder should be able to confirm this.
Read our guide to loft conversion costs to discover how much you can expect to spend
Which houses can't have a loft conversion?
If your roof space isn't tall enough, or you live in a conservation area, national park, area of outstanding national beauty or similar, the issue of planning permission for a loft conversion may be more complicated.
You can ask a builder, architect or surveyor to visit your home and check this out for you, but there are a couple of assessments you can carry out yourself prior to this. Read Can my loft be converted? to find out more.
Another great way to get a sense of whether your loft can be converted is by seeing whether any similar properties on your street have had theirs converted already. If you do spot examples, it's more likely to be a possibility.
Which loft conversion building regulations do I need to follow?
Regardless of whether or not you need planning permission, your loft conversion has to meet building regulations.
These are in place to make sure any work done is structurally sound, the new room is fire-safe and that sound is reasonably insulated between the loft and the rooms below.
The specific regulations that apply will depend on the type of conversion you have.
As a starting point, the elements covered by building regulation include:
- Fire safety: fire-resistant doors will be needed to make the new room fire-safe. Mains-powered smoke alarms will also be needed.
- Floor and beams: it's likely that new floor joists will be needed to support the weight of the new room.
- Sound insulation: it's important to make sure that noise between rooms is sufficiently minimised.
- Stairs: new stairs will be needed to provide escape in the event of a fire (a retractable staircase or ladder aren't enough).
- Walls: any new walls will need to support any existing or new roofs where existing supports have been removed.
- Windows: they need to be big enough, providing an escape route in case of fire
- Bathroom: if you're adding a new one, there are regulations regarding the plumbing and electrics
- Thermal installation: there are regulations relating to insulation.
This isn't the complete list – there are plenty more things to be taken into consideration when planning your conversion.
You can find further information by visiting the Planning Portal, or by speaking with your builder, architect or local building control.
See how to plan a loft conversion for further advice on making sure your conversion runs smoothly
Will I need a party wall agreement for a loft conversion?
If the work you're planning is going to affect the wall that joins your house to your neighbour's, you'll need to have a party wall agreement. This is an agreement between you and your neighbour that aims to ensure the work done is fair and won't endanger your neighbour's property.
You'll need to give a Party Wall Notice – a summary of your proposed work and copies of your plans – to your adjoining neighbours. You can find free templates for these online, or get help from your builder or architect. It's then up to your neighbour to sign the agreement.
If they are concerned, they may request an independent party wall surveyor to approve the work. You can recommend a surveyor, but it's ultimately up to them to decide who they use, and you're obliged to pay for their services.
The surveyor will come and inspect the plans and may request further documentation before signing off the work to go ahead or asking for any reasonable amendments to be made.
You can find out more about the Party Wall Act 1966 and what it covers by visiting the government planning website.
Read more about party wall agreements and how to keep the peace with neighbours during building work
Will I need a bat survey for a loft conversion?
If you think you have bats living in your loft, you'll need to have a bat survey, which can cost £300-£400.
Bats are a protected species and, if your loft is home to a roost of them, you may need to obtain a mitigation licence to carry out the work.