Do You Need Planning Permission, a Building Warrant or Both?

If you’re thinking about adding a garden room, shed, or summerhouse, there are two different approvals you might need. It is easy to confuse them, but they cover different things

• Planning Permission deals with where you put the building and what it looks like to your neighbours.

• Building Standards (a Building Warrant) deal with how the building is built—its safety, strength, and insulation.

Depending on the size and use of your garden room, you might need one, both, or neither.

1. Planning Rules (The "Neighbour Test")

Many houses have "Permitted Development" rights. This means you can often build small outbuildings without asking the council for permission.

To avoid a planning application, your garden building must meet all of these rules:

• It must be located in the back garden (behind the front wall of your house).

• It must not cover more than 50% of your total garden area.

• It cannot be used as a self-contained home (no sleeping or living in it full-time).

• Height Rules:

• If it has a pitched roof, the top height is max 4m.

• If it has a flat roof, the top height is max 3m.

• Crucial Rule: If any part of the building is within 1m of a fence or boundary, the height of that part cannot be higher than 2.5m.

• Protected Areas: If you live in a Conservation Area or Listed Building, stricter rules apply (usually limiting the footprint to just 4m² before you need permission).

Living in a Flat?

If you live in a flat, "4-in-a-block", or maisonette, you generally do not have these permitted development rights. You will almost always need to apply for full planning permission for a garden building, even in a private back garden.

2. Building Warrants (The "Safety Test")

Building Standards are a completely separate set of rules. A Building Warrant is the legal permission that proves your design is safe, warm, and structurally sound.

You are exempt from needing a warrant (i.e., you don't need to apply) if your garden building meets all of these conditions:

• Size: It is single-storey, detached, and 30m² or smaller.

• Use: It is not used for sleeping.

• Facilities: It has no fixed combustion appliance (like a wood-burning stove) and no plumbing (toilet/sink).

• Distance from House: sits at least 1m away from your house.

• For Flats: It sits at least 3m away from the building and at least 1m away from the boundary.

• Fire Safety: If any wall is within 1m of a boundary, it must be structurally fire-resistant and clad in non-combustible material (like cement board or brick, not standard timber).

When do you need a warrant?

If your room is bigger than 30m², closer to the house/boundary than allowed, or includes a wood burner or toilet, you must apply for a warrant.

The Cost of Compliance

Getting the warrant approved involves a fee, but the real cost is the construction. A building that meets warrant standards is effectively built to the same quality as a house extension. This means:

• Thicker insulation in walls, floor, and roof.

• Stronger foundations (concrete slab).

• Specific ventilation and electrical certification.

• Fire-rated materials if near a fence.

3. Why you should check both

It is possible to pass one set of rules but fail the other.

• Example: You might design a room that is low enough for Planning (under 2.5m), but because it has a wood-burning stove, it legally requires a Building Warrant.

• Example: You might build a large room for a flat that gets Planning Permission, but because it is within 1m of the fence, it fails the exemption for a Warrant and needs full technical approval.

4. Costs and Fees (2025 Rates)

• Planning Fee: The council fee for a standard householder application is currently £357. Decisions typically take 8–12 weeks.

• Warrant Fee: This is based on the value of the works. For a standard garden room project, fees typically start from around £150–£200, but this does not include the cost of upgrading the build materials to meet the stricter standards.

What We Charge

If you only need planning permission (and not a warrant), we can usually build to our standard garden room specification.

• We offer a fixed-price service for £965 for our standard models. This covers the council fee (£357), drawings, and managing the application for you.

• For a bespoke build, our planning application service starts from £1,395.

We are happy to have an initial discussion free of charge to find out what’s best for your project.

5. Handy Tips for a Smooth Build

• The "1 Metre Rule": If you want to build right up to your fence (within 1m), you are limited to 2.5m in height, and you likely need non-combustible cladding (like cement weatherboard) on that side to comply with fire regulations.

• Don't Guess: A couple of centimetres can make the difference between an exempt build and an illegal one.

• Future Proofing: Even if you don’t need a warrant, we always recommend building to a high standard to ensure your room is warm and weatherproof year-round.