Building Regulations Checker
Building Regulations Checker
Building Regulations Checker
FAQs
Common questions
Common questions
How much does a home extension cost in the UK?
Extension costs vary significantly based on size, specification, and location. As a rough guide, single-storey extensions typically cost £1,500 to £2,500 per square metre. Two-storey extensions cost £1,800 to £3,000 per square metre. A typical 20 square metre single-storey rear extension costs between £30,000 and £50,000. London and the South East are 20% to 40% more expensive than other regions.
What factors affect extension costs?
The main factors are size, number of storeys, build complexity, specification level, and location. Structural changes like removing load-bearing walls add cost. High-end kitchens or bathrooms within the extension increase the price significantly. Difficult access, sloping sites, and poor ground conditions also push costs up. Your choice of materials, windows, and finishes has the biggest impact on final price.
How much does a single-storey rear extension cost?
A basic single-storey rear extension costs £1,500 to £2,000 per square metre. Mid-range specifications with bi-fold doors and a good kitchen run £2,000 to £2,500 per square metre. High-end finishes push this to £2,500 to £3,500 per square metre. For a typical 4m x 5m (20 sqm) extension, expect to pay £30,000 to £70,000 depending on specification.
How much does a two-storey extension cost?
Two-storey extensions cost £1,800 to £3,000 per square metre, but you get double the floor space for less than double the price since you share foundations and roof costs. A typical 3m x 6m two-storey extension (36 sqm total) costs £65,000 to £110,000. They offer better value per square metre than single-storey if you need the space.
What are the hidden costs of building an extension?
Common hidden costs include planning permission (£258), building regulations (£500 to £1,000), architectural drawings (£1,500 to £5,000), structural engineer fees (£500 to £1,500), Party Wall Act surveyors (£700 to £1,500 per neighbour), building control inspections, utility diversions, skip hire, and temporary accommodation if needed. Budget an extra 10% to 15% for contingencies.
How much do architect fees cost for an extension?
Architects typically charge 7% to 15% of the build cost, or a fixed fee of £3,000 to £10,000 for a standard extension. Architectural technologists and designers charge less, usually £1,500 to £5,000. The fee covers initial designs, planning drawings, building regulations drawings, and may include project management. Get quotes based on your specific project scope.
Is it cheaper to extend or move house?
Moving house typically costs 8% to 10% of the property value in fees, stamp duty, and expenses. For a £400,000 house, that's £32,000 to £40,000 before buying somewhere bigger. An extension often costs similar money but adds value to your current home without the disruption of moving. Extensions make most financial sense when you like your location and the cost is less than the value added.
How can I reduce extension costs?
Keep the design simple with a straightforward rectangular footprint. Choose a flat roof instead of pitched, which costs less to build. Stick to standard window sizes. Avoid moving drainage or gas mains if possible. Get three to five quotes and compare like for like. Consider a main contractor versus managing trades yourself. Phase the work if budget is tight, completing the shell first.
How much value does an extension add to a house?
A well-designed extension typically adds 50% to 75% of its cost to your property value. A £50,000 extension might add £25,000 to £37,500 in value. Adding a bedroom or bathroom generally adds more value than extending a living space. Quality of finish matters significantly. Over-extending for your street can limit returns, so check comparable sold prices before committing.
What is included in extension cost per square metre quotes?
Cost per square metre typically includes foundations, walls, roof, windows, doors, basic electrics, plumbing, plastering, and decoration. It usually excludes kitchen units, bathroom fittings, flooring, planning fees, professional fees, and landscaping. Always clarify what's included when comparing quotes. A cheap headline rate often excludes items that push the final cost much higher.
What are building regulations?
Building regulations are legal standards that ensure building work is safe, energy efficient, and accessible. They cover structural stability, fire safety, insulation, ventilation, drainage, and electrical safety. Unlike planning permission, which controls what you can build, building regulations control how you build it. Most significant building work in England and Wales requires building regulations approval.
Do I need building regulations for an extension?
Yes. All extensions require building regulations approval regardless of whether they need planning permission. This includes single-storey rear extensions, two-storey extensions, and side extensions. Building control will assess foundations, structural work, insulation, ventilation, electrics, and drainage. You cannot sell your home without proof of building regulations compliance for extension work.
What is the difference between building regulations and planning permission?
Planning permission controls what you can build, where, and how it looks. Building regulations control how you build it, ensuring safety and efficiency standards are met. You may need both, one, or neither depending on your project. A rear extension might not need planning permission under permitted development but will always need building regulations approval.
How much does building regulations approval cost?
Building regulations fees vary by council and project size. For a typical extension, expect to pay £400 to £900 for a full plans application or £300 to £700 for a building notice. Larger projects cost more. Fees cover the plan checking stage and site inspections during construction. You can also use a private approved inspector, whose fees are often similar.
What is the difference between a building notice and full plans?
A building notice lets you start work 48 hours after notifying the council, with no upfront plan approval. It's quicker but riskier as problems are found during construction. Full plans involves submitting detailed drawings for approval before work starts. You get formal approval and certainty before building. Full plans is recommended for complex projects or if you want documented approval.
What happens if I build without building regulations approval?
Building without required approval is illegal and creates serious problems. Your council can require you to expose or undo work for inspection, or even demolish non-compliant structures. When selling, buyers' solicitors will request compliance certificates. Missing certificates can delay or collapse sales. You may need an indemnity insurance policy or retrospective regularisation, which costs more than doing it right initially.
Do I need building regulations for a loft conversion?
Yes. Loft conversions always require building regulations approval. Key areas include structural floor strength, fire escape routes, stairs, sound insulation between floors, thermal insulation, and headroom. Fire safety is particularly important as the loft becomes a third storey requiring protected escape routes, fire doors, and interconnected smoke alarms.
Do I need building regulations for a garage conversion?
Yes. Converting a garage to habitable space requires building regulations approval. The garage floor typically needs upgrading for insulation and damp proofing. Walls need insulating to current standards. Ventilation, electrics, and fire safety must all comply. The new room must meet thermal efficiency standards, which usually means significant upgrades to the existing structure.
What does a building control inspector check?
Inspectors check work at key stages including foundations, damp proof course, drainage, structural elements before covering, insulation before plastering, and final completion. They verify that work meets regulations for structure, fire safety, insulation, ventilation, drainage, and electrics. You must notify building control before covering up work or they cannot sign it off.
How long does building regulations approval take?
For a full plans application, councils aim to assess plans within 5 weeks, or 8 weeks if you agree an extension. Complex applications may take longer. A building notice has no approval stage, so you can start 48 hours after submission. The overall process depends on your build timeline, as inspections happen throughout construction. Final completion certificates are issued after the last inspection.