Short answer: yes. Nearly every house extension, loft conversion and structural alteration in London needs Building Regulations approval, even when planning permission is not required. The approval covers structure, fire safety, insulation, ventilation, drainage and electrics, and it ends with a completion certificate that you will need when you sell or remortgage.
We are Excel Construction, a Croydon-based builder working across Central London, South London and Surrey. This guide explains how Building Regulations work for house extensions and loft conversions, who signs the work off, and what to ask your builder before you sign a contract.
Building regulations vs planning permission: what is the difference?
Homeowners often mix these up, and they are two separate approvals:
- Planning permission decides whether the project is acceptable in terms of size, appearance and impact on neighbours and the street. Many projects fall under permitted development and need no application.
- Building Regulations approval decides whether the work is built safely and to the required standard. This applies to almost all extensions and loft conversions, including those built under permitted development.
- Party Wall notices are a third, separate process if you build on or near a shared boundary. Read our party wall agreement guide for how that works.
Which projects need building regulations approval?
- Rear, side-return and wrap-around extensions
- Loft conversions, including dormers and hip-to-gable work
- Removing or altering load-bearing walls
- Basement conversions and underpinning
- Flat roof replacements that change the structure or insulation
- New-build homes, see our new-build house guide
- Changes to drainage, new bathrooms and some electrical work
What do building control inspectors actually check?
The exact list depends on the project, but for a typical extension or loft in a London home inspectors look at:
- Structure: foundations, steel beams, floor and roof structure, usually backed by an engineer’s calculations
- Fire safety: protected escape routes, fire doors, smoke alarms and, in lofts, a safe route down to the front door
- Energy efficiency: insulation levels, glazing and heating
- Ventilation and damp: extractor fans, trickle vents and damp proofing
- Drainage: new connections and building over or near existing drains
- Electrics and stairs: safe installation, headroom and stair dimensions
Full Plans or Building Notice: which route is better?
There are two common ways to apply. A Full Plans application means the drawings and structural details are checked and approved before work starts, which gives certainty and is usually the better choice for extensions and lofts. A Building Notice lets work start sooner with no plan check, but it puts more risk on you if an inspector later asks for changes. We generally recommend Full Plans for anything structural.
Local council or Approved Inspector?
Your council’s Building Control team (for example Croydon, Sutton, Bromley or Merton) can inspect your work, or you can appoint a private Approved Inspector. Either route ends in a completion certificate. Ask your builder which they use and who is responsible for booking inspections.
Why the completion certificate matters
When the project is finished and passes its final inspection you receive a completion certificate. Keep it with your deeds. Buyers’ solicitors will ask for it, and without it a sale or remortgage can stall. If you are comparing builders, our 7 biggest mistakes homeowners make when hiring a contractor is a useful checklist, and main contractor vs separate trades explains who carries responsibility for sign-off.
Building regulations checklist before you hire a builder
- Ask who submits the application and who books each inspection
- Ask whether structural calculations and drawings are included in the quote
- Ask how and when you will receive the completion certificate
- Check the builder has experience of your area and council
- Ask to see recent projects in our project gallery and read client testimonials
Building regulations by project type
Cost and planning questions come up alongside Building Regulations on most projects, so these guides are worth reading together: loft conversion cost guide, kitchen extension cost guide, house extension cost guide and flat roof guide.
Areas we cover
We manage Building Control for projects in Croydon, Purley and Coulsdon, Sutton and Cheam, Wimbledon and Morden, Kingston and Surbiton, Bromley and Beckenham, Clapham and Streatham and Epsom and Esher, plus the wider South London and Surrey.
Frequently asked questions
Do I need building regulations approval for a house extension in London?
Yes. Almost every extension needs Building Regulations approval, whether or not it also needs planning permission. The two are separate systems: planning looks at how the extension affects the street and neighbours, while Building Regulations check that the work is structurally safe, energy efficient, properly drained and fire safe.
Do I need building regulations for a loft conversion?
Yes. A loft conversion changes the structure of the house and creates a new habitable floor, so it needs Building Regulations approval. Key checks include the floor structure, a protected escape route down the stairs, fire doors, insulation, ventilation and safe stair access.
Who signs off building regulations in London?
Your local council’s Building Control team or a private Approved Inspector can inspect the work and issue the completion certificate. Your builder should tell you which route they are using before work starts.
What happens if I build without building regulations approval?
The council can require work to be opened up, altered or removed, and a missing completion certificate commonly causes problems when you sell or remortgage. It is far easier to get approval before and during the build than to fix it afterwards.
Is building regulations approval the same as planning permission?
No. Some extensions and loft conversions are built under permitted development and need no planning application, but they still need Building Regulations approval. See our guide to loft conversion planning permission in London and Surrey for the planning side.
Does Excel Construction handle building regulations?
Yes. We coordinate drawings, structural design and Building Control inspections as part of the project so you are not chasing different people. Call 03303 110740 to arrange a free site visit.
Get a free site visit and written quote
Call 03303 110740 (Mon–Sat, 9am–5pm) or use the quote form below. We will handle drawings, structural design and Building Control for you.