Outbuildings
What Size Outbuilding Can I Build Without Planning Permission? (2025)
Garden rooms, sheds, home offices, workshops — how big can they be? The answer depends on height, position, and how much of your garden is already covered. Here are the exact limits.
⏱ 5 min read
📅 Updated June 2025
🏠 England only
The Quick Size Limits
Under permitted development (Class E, GPDO 2015), there is no absolute maximum footprint for an outbuilding. Instead, the rules use a combination of:
- Height limits — which vary depending on roof type and distance from the boundary
- A 50% garden coverage limit — your outbuilding(s) cannot cover more than half your original garden
- Position restrictions — outbuildings cannot be in front of the principal elevation
Within these parameters, you have significant freedom on the size and footprint of your outbuilding.
✅ No maximum footprint in the rules
There is no rule saying “your shed must be smaller than X square metres”. The limits are height, garden coverage, and position. A very large garden could accommodate a large outbuilding without any planning permission — provided the 50% rule and height limits are observed.
Height Rules in Detail
| Roof Type / Location |
Maximum Eaves Height |
Maximum Overall Height |
| Dual-pitched roof (anywhere in garden) |
2.5 metres |
4 metres |
| Any other roof type (flat, mono-pitch, etc.) |
2.5 metres |
3 metres |
| Any structure within 2m of a boundary |
— |
2.5 metres maximum |
The eaves height restriction of 2.5 metres applies everywhere. The overall height limit then depends on the roof type. But if the outbuilding is within 2 metres of any boundary, the overall height — regardless of roof type — must not exceed 2.5 metres.
Note that height is measured from natural ground level — not from any raised base or platform. If you’re installing a deck or raised base, be careful that the combined structure doesn’t breach the height limits.
The 50% Coverage Rule
This is where many plans run into problems. The total footprint of all outbuildings and extensions combined must not exceed 50% of the curtilage of the original dwelling house (i.e., the garden when the house was built, excluding the footprint of the house itself).
What’s included in the calculation?
- All existing outbuildings — sheds, garages, greenhouses, summerhouses
- Any extensions already added to the house
- The new outbuilding you want to build
- Any garden structures with a roof (pergolas without a solid roof may not count)
What’s excluded?
- The original footprint of the house
- Patios, paths, and decking at ground level
- Open fences, walls, and gates
⚠️ Smaller gardens have less room
In a small urban garden of 50m², you can only cover 25m² with outbuildings and extensions combined. If you already have a 6m² shed, only 19m² is left for your new garden room. In a larger rural garden of 400m², you could potentially build a 200m² outbuilding.
Real-World Size Examples
| Garden Size |
Max Total Outbuilding Coverage |
Existing Shed (6m²) |
Available for New Build |
| 50m² (small urban) |
25m² |
6m² |
19m² |
| 100m² (average suburban) |
50m² |
6m² |
44m² |
| 200m² (larger suburban) |
100m² |
6m² |
94m² |
| 500m² (large/rural) |
250m² |
6m² |
244m² |
These figures assume no extensions have been added to the house (extensions also count against the 50% allowance). If you’ve already added a 30m² extension to your 200m² garden plot, only 70m² is left for outbuildings.
The 2-Metre Boundary Rule
The 2-metre boundary rule is one of the most tripping points for homeowners. If your outbuilding — or any part of it — is within 2 metres of your property boundary, the maximum height of the structure drops to 2.5 metres.
This limit applies to the overall height of the structure, including any ridge or peak. So a standard flat-roof garden room at 2.7m height would not comply if placed within 2 metres of the fence.
The 2-metre measurement is from the boundary — typically the fence line, but legally the boundary as recorded in the title register. The measurement is to the nearest part of the outbuilding (including any eaves overhang).
🚫 Check your garden room’s measurements carefully
Many off-the-shelf garden rooms are 2.5m to 2.8m at the ridge. If the room is within 2m of the boundary, even a 2.6m ridge height would require planning permission. Always check the precise height of any structure you’re buying.
Exceptions and Special Cases
The rules above apply to standard houses in England. The position changes in certain circumstances:
- Conservation areas, National Parks, AONBs, World Heritage Sites: Outbuildings to the side of a house require planning permission. Limits on size and position may be tighter.
- Listed buildings: Any outbuilding requires listed building consent. The same size rules don’t apply.
- Flats and maisonettes: Class E does not apply to flats — any outbuilding would require planning permission.
- Article 4 Directions: Some councils have used Article 4 Directions to remove PD rights for outbuildings in specific areas.
- New build planning conditions: Some new developments have conditions removing PD rights — check your title deeds.
Frequently Asked Questions
How big can a shed be without planning permission?
There is no absolute size limit for a shed under permitted development. It must be single storey, must not exceed the height limits (max 4m with a pitched roof, 3m with a flat roof, or 2.5m if within 2m of the boundary), and combined with all other outbuildings and extensions must not cover more than 50% of the garden. It must also not be in front of the principal elevation of the house.
Is there a maximum size for a garden room without planning permission?
No specific maximum footprint exists in the planning rules. The practical limits are the 50% garden coverage rule and the height limits. A garden room could theoretically be very large if the garden is large enough and the height stays within limits. However, Building Regulations will apply to structures over 30m² (or even some smaller ones if within 1m of a boundary), which adds cost and complexity.
Does a garden room need to be a certain distance from the house?
No, planning rules don’t specify a minimum distance between an outbuilding and the main house. You could build a garden room immediately adjacent to the house. However, fire safety regulations under Building Regulations may require a minimum separation distance in some cases, particularly for larger structures or where the outbuilding wall is combustible. Your building inspector will advise on this.
Do I need planning permission for a 5x4m garden room?
A 5x4m (20m²) garden room will usually not need planning permission, provided: it stays within height limits, it doesn’t push total garden coverage over 50%, and it’s positioned in the rear or side garden (not in front of the principal elevation). Check the height carefully — if it’s within 2m of a boundary, the maximum height is 2.5m. Building Regulations approval may not be needed for a 20m² structure if it’s more than 1m from the boundary, made of non-combustible materials, and not used for sleeping.
Want More Detail on PD Rules?
Our complete permitted development guide covers outbuildings, extensions, loft conversions, and everything else you need to know.
Read the Complete PD Guide →
