Key Takeaway
Most homeowners know they need planning permission before building an extension. Far fewer understand that Building Regulations approval is a separate legal requirement — and that a full technical drawing package is what makes it possible.
Planning Permission vs Building Regulations: Two Separate Hurdles
When homeowners discover they need approval before building an extension, they usually assume the planning application is the main hurdle. Planning matters — but it only covers whether you're allowed to build something. Building Regulations are a completely separate legal framework that governs how you build it.
You can have planning permission granted and still be unable to start on site until Building Regulations are in place. Conversely, if your extension falls within Permitted Development rights and doesn't need planning permission, you still need Building Regulations approval before breaking ground. There is no exemption.
What Building Regulations Cover
Building Regulations set the minimum technical standards for construction in England and Wales. For a house extension, the relevant Parts include:
- Part A — Structure: Foundations, walls, floors, roof, beams and lintels must be structurally adequate
- Part B — Fire safety: Escape routes, smoke detection and separation of uses
- Part C — Moisture resistance: Damp proofing, drainage and weatherproofing
- Part E — Sound: Sound insulation between rooms, particularly if creating a new bedroom
- Part F — Ventilation: Fresh air provision for habitable rooms and kitchens
- Part L — Energy efficiency: Wall, floor and roof insulation standards; U-values for glazing
- Part M — Accessibility: Level access thresholds, door widths and turning circles where applicable
What Is a Building Regulations Drawing Package?
A Building Regulations drawing package is a set of detailed technical drawings prepared to the standard required by your local Building Control body (BCB). It provides the inspector with enough information to assess that your extension meets the required standards — and gives your contractor the information needed to actually build it correctly.
A complete package for a typical single-storey rear extension includes:
- Proposed floor plans and elevations — showing dimensions, room layouts, openings and the relationship to the existing property
- Construction cross-sections — detailed sections through walls, floors and roof showing the build-up: insulation layers, DPC positions, cavity width, breathable membranes and finishes
- Structural details — beam sizes, padstone specifications, lintel schedules and load-bearing wall information. Where structural engineer calculations are required, these are incorporated
- Block plan and location plan — OS-based site plans showing the footprint in context, required for the Building Notice submission
- Construction notes — written specifications covering materials, insulation performance values, drainage connections and other key requirements
Building Notice vs Full Plans Application
There are two routes to Building Regulations approval. Understanding which applies to your project can save time:
Building Notice is a simplified submission route where you notify the council of your intention to build and an inspector visits at key stages. It's suitable for straightforward extensions that don't involve complex structural work, drainage connections to public sewers, or fire safety measures. Our drawing package gives the inspector everything they need to assess compliance at each stage visit.
Full Plans Application involves submitting detailed drawings in advance for the BCB to approve before work begins. This takes longer upfront (typically 5 weeks) but gives you a formal approval document that confirms compliance before any money is spent on construction. It's recommended for more complex projects or where you want certainty before tendering.
Hampshire Build prepares drawing packages suitable for both routes. During your consultation, we'll advise which approach is right for your project.
What Happens Without Proper Drawings?
Some builders offer to "sort out the building regs" themselves, or suggest you can start work on a Building Notice without detailed drawings. This is a false economy. Without proper technical drawings:
- Your contractor doesn't have the information needed to build correctly — particularly for structural elements and insulation
- Building control inspectors can and do stop work if they cannot verify compliance
- You may face costly remedial work if construction doesn't meet standards
- When you come to sell, your solicitor will need evidence of Building Regulations compliance — without it, you may struggle to complete
Hampshire Build's Fixed-Fee Building Regulations Service
Our Pre-Build Package (£1,950+VAT) includes both planning drawings and a full Building Regulations drawing package — everything you need to get on site. There are no hidden fees for structural details or additional drawings. Our fixed-fee model means you know the cost before we start.
We cover extensions, loft conversions, garage conversions and internal remodelling work across Hampshire, Surrey, Berkshire, Hertfordshire, Buckinghamshire, Oxfordshire, Wiltshire and West Sussex.
Book a complimentary consultation to discuss your project — we'll confirm the planning route, likely Building Regulations requirements, and a fixed fee for the work.
