Thinking about a garden office, shed, workshop or studio? It’s not just planning permission you need to think about – outbuildings building regulations also decide what you can safely build, when you need approval, and how to keep Building Control happy.
This guide walks you through when small structures are exempt, the size and use limits that trigger approval, how Building Control checks the work, and what to do if you’re not sure your plans are compliant.
Wondering if your outbuilding needs Building Regulations approval?
Send us your sketch or estate-agent plan and we’ll tell you what regs are likely to apply – before you spend money on the build.
Outbuildings & Building Regulations – the basics
In UK law, planning permission and Building Regulations are two separate systems. Many small outbuildings can be built under permitted development without a planning application, but the Building Regulations for outbuildings can still apply depending on size, distance to boundaries, and what the space is used for.
Building Regulations deal with safety, structure, insulation, fire protection, drainage and electrics. They exist to make sure your new garden room, shed or home office is safe to use and won’t cause problems later if you sell or remortgage.
As a very rough rule:
- Small, simple sheds under about 15 m² with no sleeping are usually exempt.
- Medium outbuildings between 15–30 m² may be exempt if they’re well away from boundaries or built in non-combustible materials.
- Larger structures, anything with sleeping accommodation, or spaces attached to the house will almost always need approval.
Because the rules are detailed, many homeowners ask, “Do outbuildings need Building Regulations approval?” The answer is: sometimes yes, sometimes no – and getting it wrong can be expensive. Our job at Plans Made Easy is to help you sit on the right side of those rules.
Planning permission vs Building Regulations for outbuildings
It helps to separate the questions clearly in your mind:
- Planning permission is about what you are allowed to build and where on the plot.
- Building Regulations are about how that structure is built and whether it is safe and energy efficient.
You can, for example, have:
- An outbuilding that is permitted development in planning terms but still needs Building Regulations approval.
- A small shed that needs no application to Building Control but does need planning permission in a conservation area.
If you are mainly worried about planning, our guides on how planning permission works, when planning permission is required and sheds and planning limits walk through those rules. This article stays focused on Building Regulations for outbuildings – but you’ll usually need to think about both together.
Ways to get Building Regulations approval for an outbuilding
Once you cross the exemption thresholds, you’ll need a formal route to Building Regulations compliance. For most domestic outbuildings in England there are three common options:
1. Full Plans application
With a Full Plans application you submit detailed drawings and specifications before building. The council (or an approved inspector) checks them and issues a decision notice confirming compliance or asking for changes.
This route is usually best for:
- Garden rooms used as home offices, studios or gyms with services (electrics, maybe plumbing).
- Larger timber buildings over 30 m².
- Any outbuilding that needs structural calculations for steelwork, long spans or unusual roofs.
Our article on plans for Building Regulations explains what a good set of drawings looks like and what should be included.
2. Building Notice
A Building Notice route skips the pre-approval of drawings. You notify Building Control about 48 hours before starting, then they inspect on site at key stages.
This can work for straightforward projects with an experienced builder, but it gives you less certainty up-front. If Building Control wants changes once you’ve started, altering work can be disruptive and costly.
3. Approved Inspector / private inspector
Instead of the council, you can appoint a private Building Control body (where available) to check and sign off the work. They follow the same regulations but may offer more flexible site visit times.
What Building Regulations cover in an outbuilding
When people search for “building regulations outbuildings UK”, they’re usually trying to understand what standards actually apply. The main Parts of the regulations that affect garden structures are:
- Part A – Structure: foundations, floor slabs, walls, roof and stability in wind.
- Part B – Fire safety: fire resistance of walls and roofs, escape routes, separation distance from boundaries.
- Part F – Ventilation: background trickle vents, opening windows and extract fans where needed.
- Part L – Conservation of fuel & power: insulation levels, thermal bridges and glazing performance.
- Part P – Electrical safety: certification of fixed wiring in domestic outbuildings.
- Part M – Access: level thresholds and steps may be relevant if the outbuilding is intended for regular use.
For simple sheds storing tools, most of these will not be triggered because the structure is exempt. However, as soon as you create a comfortable workspace or hobby room used regularly, the standards above start to matter.
If you’d like to go deeper into the regulations in general, our Building Regulations homeowner guide and Building Control overview explain how they work across all types of home projects.
Typical costs & timelines for outbuilding Building Regulations
Costs vary by local authority and by the size and complexity of your project, but homeowners usually need to budget for:
- Drawings and specifications: From a few hundred pounds for simple plans up to four figures for complex garden rooms with plumbing and structural steel.
- Building Control fees: Often split into a plan-check fee and an inspection fee. For small domestic work this is commonly in the low hundreds, but larger projects cost more.
- Additional reports: Structural calculations, energy assessments or drainage designs where needed.
- Basic shed or small store, exempt – no Building Control fees, but you still pay to build it safely.
- Garden office 20–25 m² with electrics – drawings plus Building Control can easily reach £1,000–£2,000 combined.
- Larger outbuilding with bathroom or kitchenette – expect higher costs and more inspections.
For wider build budgets, our guides to extension costs and single storey projects give useful context.
In terms of timing:
- Full Plans applications are typically checked within 5–8 weeks.
- Building Notices allow you to start after 48 hours, but you carry more on-site risk if changes are required.
- Site inspections happen at key stages – foundations, floor, structure, insulation and completion.
Not sure if your idea fits Permitted Development and Building Regulations?
Send us a few photos and rough dimensions – we’ll flag whether you’re likely exempt or if you should budget for a Building Regulations application.
Step-by-step checklist for a compliant outbuilding
Here’s a simple process you can follow before you order a garden building or start digging foundations.
| Step | What to check |
|---|---|
| 1. Clarify the use | Is it storage only, a hobby room, a heated office, or somewhere people might sleep? The use has a huge effect on whether Building Regulations apply. |
| 2. Measure the floor area | Calculate internal floor area in square metres. Note whether you are under 15 m², between 15–30 m², or above. |
| 3. Check distance to boundaries | Measure from the proposed walls to fences or neighbour buildings. Structures close to boundaries are more likely to need Building Regulations for fire safety. |
| 4. Confirm planning status | Use the Planning Portal and our guides on sheds, garden rooms and planning permission to see if the structure is permitted development. |
| 5. Decide if Building Regulations apply | Use the size/use rules in this guide, or contact Building Control or our team if you are unsure. Err on the side of caution where people will work or sleep in the space. |
| 6. Prepare drawings | Get scaled plans, elevations and sections prepared. Our articles on planning drawings and drawings for applications explain what’s normally required. |
| 7. Submit and keep records | Submit your Full Plans or Building Notice, follow inspection advice, and keep every approval letter and completion certificate for future sales. |
Common pitfalls with outbuildings and Building Regulations
1. Treating a home office as a bedroom
Using a garden room for occasional guests may feel harmless, but sleeping use triggers stricter fire and insulation rules. If the building sits near a boundary or has limited escape routes, it may not comply without alterations.
2. Building too close to the boundary
An outbuilding constructed from combustible materials (typical timber garden rooms) within 1 m of the boundary is much more likely to need Building Regulations approval. Fire spread between properties is one of the key risks that regulators worry about.
3. Assuming small size means no rules
Homeowners often ask, “How big can an outbuilding be without planning permission or Building Regulations?” There isn’t a single magic dimension. Size, use and distance to boundaries all interact. A 14 m² heated office close to a fence may be more problematic than a 25 m² unheated store built in non-combustible materials further away.
4. Uncertified electrics
Even when the structure itself is exempt, new wiring in a garden building usually needs to be certified under Part P. Make sure you use a suitably registered electrician and get the paperwork at the end.
Key technical limits for outbuildings
The detailed rules can be complex, but these headline points are a useful starting checklist when thinking about outbuildings building regulations in England:
- Under 15 m² floor area: Generally exempt if single storey, detached, and with no sleeping accommodation.
- Between 15–30 m² floor area: May be exempt if single storey, detached, no sleeping, and either at least 1 m from the boundary or substantially non-combustible.
- Over 30 m² floor area: Almost always requires Building Regulations approval.
- Any size with sleeping: Treated more like habitable accommodation – expect full compliance.
- Attached structures: If an outbuilding is physically attached to the house, it is usually treated as an extension rather than a separate structure.
If your property is in a conservation area or you have a listed building, there may also be heritage controls. Our guides to conservation areas and works on listed homes explain how those extra layers sit alongside Building Regulations.
FAQs: Outbuildings and Building Regulations
Do outbuildings need Building Regulations approval?
Some do, some don’t. Small, simple, detached structures under 15 m² with no sleeping accommodation are usually exempt. Between 15–30 m² you may also be exempt if the outbuilding is at least 1 m from the boundary or built in non-combustible materials. Anything larger, attached to the house, or used for sleeping will normally require approval.
Do you need Building Regulations for a shed?
Most typical garden sheds used purely for storage and under 15 m² do not need Building Regulations approval, as long as they are single storey, detached and not used for sleeping. However, if you insulate, heat and wire the shed as a home office or hobby space, or if it grows larger than those limits, the position changes.
How big can an outbuilding be without Building Regulations?
There is no single number. The commonly-quoted figures are:
- Under 15 m² – generally exempt if detached and no sleeping.
- 15–30 m² – possibly exempt if detached, no sleeping and either 1 m+ from boundary or built in non-combustible materials.
Over 30 m² or anything with sleeping accommodation will almost always need approval. When in doubt, check with Building Control – they can confirm for your exact proposal.
Can you build an outbuilding without planning permission but still need Building Regulations?
Yes. It’s quite common for a garden office or workshop to fall within permitted development in planning terms, while still needing Building Regulations approval because of its size, construction, or intended use. Always treat planning and Building Regulations as two separate checks.
Can an outbuilding be attached to the house?
You can physically connect a new structure to the house, but the moment you do, Building Control will treat it more like an extension. That means stricter rules on insulation, structure and fire separation. In many cases it’s simpler to keep the outbuilding fully detached with a small gap.
Are outbuildings subject to Building Regulations in a conservation area?
Building Regulations are about safety and apply regardless of whether you are in a conservation area. However, heritage controls may restrict the appearance, height or location of the structure. You may also find it harder to rely on permitted development. Always check with the local authority before committing.
How often do Building Regulations change?
Major updates are not constant, but parts such as energy efficiency (Part L) and fire safety (Part B) are reviewed periodically. It’s one reason online advice about outbuildings building regulations can go out of date. If you’re planning a project, make sure you rely on current guidance or talk to a professional.
Key facts snapshot – outbuildings & Building Regulations
- Small sheds < 15 m² Usually exempt if single storey, detached and with no sleeping accommodation.
- 15–30 m² garden rooms May be exempt if detached, no sleeping and either 1 m+ from boundary or largely non-combustible.
- Over 30 m² or any sleeping use Expect to need Building Regulations approval and full compliance with Parts A, B, F, L, P and others.
- Electrics in outbuildings Wiring is normally notifiable under Part P – use a registered electrician and keep the certificates.
- Planning vs Building Regulations A structure can be permitted development in planning terms but still require Building Regulations approval.
- Paperwork to keep Approval notices, inspection reports and the final completion certificate – vital when you sell or remortgage.
Unsure where your project sits? Plans Made Easy can review your sketch and advise whether your outbuilding is likely to be exempt or needs Building Regulations approval.
Next steps & useful guides
If you’re planning a garden room, shed, studio or similar, these guides on Plans Made Easy will help you join the dots between planning permission, Building Regulations and costs:
- Building Regulations – complete homeowner’s guide
- Building Control – what it is and how inspections work
- Rules for sheds – sizes, locations and council quirks
- Building Regulations for garden rooms
- Garden rooms – planning and design overview
- Planning permission for a garden room
- Planning permission costs and making plans the right way if you’re at early design stage.
Official guidance & further reading
For the most up-to-date national rules on planning and Building Regulations, you can also check:
Need help checking your outbuilding design?
We can review your sketch, highlight any Building Regulations issues and help you get plans ready for Building Control.
Bringing it all together
Outbuildings can be a brilliant way to gain storage, workspace or leisure space without the disruption of a full extension. However, outbuildings building regulations still matter – especially once you add heating, electrics or sleeping space, or when the structure grows beyond the smallest shed.
By checking size, use and position early, choosing the right approval route, and keeping your paperwork in order, you can enjoy your new garden room with confidence that it’s safe, legal and sale-friendly in future.
Ready to move your project forward?
Plans Made Easy can prepare compliant plans, manage submissions, and guide you from idea to approval.
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