Garden Buildings: Sheds, Offices, Gyms and Studios — The Rules

Usually, no. Most garden buildings — including offices, gyms, studios, and summer houses — are permitted development under Part 1, Class E of the GPDO 2015, as long as they meet the size and position rules.

The key requirement is that the building must be “incidental to the enjoyment of the dwellinghouse.” This is the single most important test. A garden office used by the homeowner for working from home is generally accepted as incidental. A building designed as a separate dwelling, a business premises with employees and customers visiting, or a rental unit is not.

The 50% curtilage rule explained

This trips up more homeowners than any other outbuilding rule. The total area of ground covered by all buildings behind the principal elevation — including your extension, your existing shed, your garage (if behind the front), and the new garden building — must not exceed 50% of the total curtilage of the original house.

“Curtilage” means the land around the house that forms part of the property — essentially your garden and driveway. “Original house” means the house as first built or as it stood on 1 July 1948.

If a previous owner built a large extension, that might have already used up most of your 50% allowance.

Height near boundaries

If the garden building is within 2 metres of any boundary, the maximum height drops to 2.5 metres. This applies to the ridge of the roof, not just the eaves. Many garden office companies sell buildings that are 2.5m to the ridge specifically to comply with this rule.

• The building exceeds the height limits (4m dual-pitched, 3m other, or 2.5m within 2m of a boundary)
• The building would push the total ground coverage over 50% of the curtilage
• The building is forward of the principal elevation
• The building is not incidental to the dwelling — for example, it is a self-contained living unit, a business with visiting customers, or a rental property
• Your property is a listed building (you also need listed building consent)
• An Article 4 direction removes outbuilding PD rights
• Your PD rights have been removed by a planning condition
• The building is a flat or maisonette (no Part 1 PD rights)

A householder planning application costs £548.

Many garden buildings do not need building regulations approval. The exemptions are:

What “no sleeping accommodation” means

If you intend to use the garden building as a bedroom, guest room, or annex with a bed, building regulations will apply regardless of size. A garden office with a sofa that occasionally has someone sleep on it is a grey area — but if the building is designed or marketed as sleeping accommodation, it needs building regulations.

When building regs do apply

If your garden building does need building regulations (because it is over 30m², has sleeping accommodation, or is close to a boundary), the requirements typically cover:

• Structural stability
• Fire resistance (especially walls and roof close to boundaries)
• Electrical safety (Part P — if the building has its own electrical supply)
• Drainage (if the building has a WC or sink)
• Energy efficiency (Part L — for heated buildings)

Electrical work

If you are running electricity to the garden building from your house, the electrical installation must comply with Part P of the building regulations. This applies to new circuits — not just the building itself. The work must be done by a qualified electrician registered with a competent person scheme (such as NICEIC, NAPIT, or ELECSA), or you must apply for building regulations approval separately.

One of the most common concerns: does running a business from a garden office need planning permission?

In most cases, no. If you are working from home in your garden office — doing desk work, making calls, using a computer — this is generally considered incidental to the residential use of the property. No change of use is needed.

It becomes a planning issue when:

• Customers or clients regularly visit the garden office
• Employees come to work in the building
• Deliveries and commercial activity generate traffic, noise, or other impacts on neighbours
• The building is used for manufacturing, storage for a commercial business, or other activities that go beyond typical home office use

The test is whether the character of the property has changed. If a neighbour or council officer could not tell from outside that any business was being run, you are almost certainly fine.

You cannot use a garden building as a separate dwelling under permitted development. A building that is “incidental to the enjoyment of the dwellinghouse” is by definition not a separate dwelling.

If you want to create a self-contained annexe (with its own kitchen, bathroom, and sleeping accommodation), you will almost certainly need planning permission. The council will consider whether it constitutes a new dwelling — which has implications for:

• Council tax — a separate dwelling triggers a separate council tax bill
• Building regulations — full compliance required, including fire safety, insulation, drainage, and accessibility
• CIL (Community Infrastructure Levy) — may apply to new dwellings

Foundations

Most garden buildings sit on a concrete slab, concrete pads, or ground screws. A properly prepared base is essential — an uneven or inadequate base will cause the building to shift and water to pool.

For buildings over 15m², consider a proper concrete slab with a damp-proof membrane.

Drainage

If the garden building has hard-standing around it or a large roof area, you may need to consider surface water drainage — particularly if you are in a flood risk area. In most cases, rainwater can discharge to a soakaway or permeable ground within your garden.

Services

Running water, electricity, and broadband to a garden building adds cost but makes the space genuinely usable. Budget £1,500–£4,000 for a proper electrical supply and insulation that makes the building comfortable year-round.

Additional costs:

• Groundworks and base: £1,000–£3,000
• Electrical supply: £1,500–£3,000
• Plumbing (if needed): £2,000–£5,000
• Building regulations fees (if applicable): £400–£900

1. Ignoring the 50% rule. Count up everything behind the front of the house — the shed, the garage, the existing extension, and the proposed garden building. If it exceeds 50% of the curtilage, you need planning permission.

2. Building too high near a boundary. Within 2 metres of a boundary, the maximum height is 2.5 metres — not 3m or 4m. Many off-the-shelf garden offices are designed to just meet this limit, but check before you buy.

3. Assuming it is a change of use. Working from a garden office does not usually require a change of use application. But having customers visit regularly or employing staff there may do.

4. Not getting building regulations when needed. If the building is over 30m² or has sleeping accommodation, you need building regulations. Ignoring this creates problems when you sell.

5. Not getting an LDC. A Lawful Development Certificate costs £274 and gives you official confirmation that the building is lawful. It is invaluable when selling. Our PD Certificate Report can help.

1. Check your property using our free PD checker
2. Read our PD rules guide to understand the limits in detail
3. Protect your build — our PD Certificate Report helps you apply for an LDC