Building Regulations in the UK: What You Need Approval For

Planning permission gets most of the attention, but building regulations are the system that governs how your project is actually built. Many homeowners are surprised to find that works can need building regulations approval even when no planning permission is required — and that skipping this step can cause serious problems when you come to sell.

Building Regs vs Planning Permission: Two Separate Systems

Planning permission controls whether a development is appropriate in its location. It is administered by the Local Planning Authority.

Building regulations control how a building is constructed — its structural integrity, fire safety, insulation, drainage, electrical installation, and ventilation. They are administered by Building Control, which may sit within the council or be provided by a Registered Building Inspector.

You can need one without the other, or both. A rear extension typically requires both planning permission and building regulations approval. Replacing like-for-like windows usually requires neither. Installing a new boiler requires building regs but rarely planning permission.

What Always Requires Building Regulations Approval

• Extensions to a house (any size)
• Loft conversions (creating a habitable room in the roof space)
• Garage conversions to habitable space
• New dwellings or change of use to a dwelling
• Structural alterations — removing or altering load-bearing walls, forming new openings
• Electrical work — installation of new circuits, consumer units, or work in kitchens and bathrooms (Part P)
• Boiler installations and heating systems — replacement boilers, new central heating
• Cavity wall insulation and solid wall insulation
• Roof replacements on more than 25% of the total roof area
• Installation of replacement windows — unless by a FENSA or CERTASS registered installer
• Underpinning and most structural foundation work
• New or replacement drainage connecting to a sewer

What Is Exempt

• Like-for-like repairs — replacing a cracked tile, repairing plasterwork, redecorating
• Most garden structures — sheds, summerhouses, greenhouses (subject to size limits)
• Some porches — under 30m², at ground level
• Most fences, gates, and walls below certain heights
• Temporary buildings — not intended to remain for more than 28 days

If you are unsure, contact your local Building Control team for a free pre-application query.

Two Routes to Approval

Full Plans Application — You submit detailed drawings and specifications before work starts. Building Control checks them and approves or requests amendments. Work then proceeds with inspections at key stages. This route gives you certainty upfront and is recommended for complex projects.

Building Notice — You notify Building Control that work is about to start (usually 2 working days before). No drawings are submitted in advance. Inspectors visit during the works. This route is faster to initiate but riskier — if the inspector finds a problem at a late stage, you may have to undo completed work.

For most homeowners doing an extension or loft conversion, Full Plans is the safer choice.

The Inspection Stages

The Completion Certificate and Why It Matters

When all works are satisfactorily inspected, Building Control issues a Completion Certificate:

• Solicitors and conveyancers will ask for it when you sell the property
• Mortgage lenders may require it for remortgaging
• Insurers may require it for claims related to works

If you cannot produce a Completion Certificate, your solicitor may require indemnity insurance — which does not fix the underlying problem. For a full breakdown of what a Completion Certificate is, how to obtain one retrospectively, and your options if work was done without one, see our Building Regulations Completion Certificate guide — including the three routes available (regularisation, IBG, and the 10-year enforcement rule) and what conveyancers check for.

Retrospective Approval: The Regularisation Certificate

If work was carried out without approval, you can apply retrospectively for a Regularisation Certificate. The process involves Building Control inspecting the completed work — which may mean opening up walls or floors. Fees typically start at around £300 to £500.

Typical Fees (2024/25)

For basement conversion projects specifically, building regulations requirements are more complex — covering structure (Part A), fire escape, waterproofing (Part C), ventilation, and Part P electrical work. Our basement conversion costs and planning guide explains which parts apply, the difference between Full Plans and Building Notice for below-ground work, and what Building Control will check at each inspection stage.

Appointing a qualified contractor who understands building regulations — and will manage the inspection stages correctly — is essential. The guide to finding and vetting a builder in the UK explains how to use FMB and TrustMark accreditation to identify contractors with the competence and insurance to deliver compliant work.

For a side-by-side explanation of when you need planning permission, when you need building regulations, when you need both, and when you need neither — with a full decision table covering 14 common project types — see our building regulations vs planning permission guide.

If you are planning an extension, loft conversion, or structural alteration, Renovate Me gives you a personalised renovation roadmap with the right tasks in the right order. Start at renovate-me.madethis.app.

Published June 2025