Building regulations for extensions
Extension guide covering structure, insulation, drainage, fire safety, ventilation and completion evidence.
Short answer
Most extensions need building regulations approval even when the planning route is permitted development. The key early decision is usually full plans versus building notice, with structure, foundations, insulation, drainage and ventilation settled before work is covered.
For the planning permission side, use UKPlanningGuide. Keep that separate from building regulations approval and completion evidence.
What usually triggers extra checks
- New foundations or altered ground levels
- Steel beams, roof structure or widened openings
- Drainage runs, public sewer proximity or new bathrooms
- Part L energy details and Part F ventilation strategy
Route options to discuss
Use full plans when you want detail checked before work starts, when the builder needs clear specifications, or where structure and energy details are not simple. A building notice may fit smaller straightforward domestic work, but it leaves more detail to be resolved on site.
Evidence to keep
- Approved drawings/specification
- Structural calculations and beam details
- Inspection records for excavations, drains, insulation and completion
- Completion certificate and installer commissioning records
Mistakes to avoid
Do not assume planning permission, permitted development or a builder's quote answers the building regulations question. Do not cover up work before required inspections. Do not rely on a certificate claim without checking who issues it and how you will receive a copy.
Common questions
Does building regulations for extensions need building regulations approval?
Often yes, especially where the work changes structure, fire safety, insulation, ventilation, drainage, electrics or heating. The exact route depends on the specification and building control body.
Can planning permission and building regulations be separate?
Yes. Planning permission controls whether development is allowed in planning terms; building regulations deal with safety, energy, ventilation, drainage, structure and completion evidence.
What should I keep for sale or remortgage?
Keep the application reference, drawings, inspection notes, photos before work is covered, installer certificates and the completion certificate or equivalent evidence.