The Extension Planning Checklist

• Define what you need — more kitchen space? An extra bedroom? A home office? Be clear on the problem you are solving.
• Set a realistic budget — use our extension cost guide to understand typical costs
• Check if your project is permitted development — this determines whether you need planning permission
• Check your property for constraints — conservation area, listed building, Article 4 directions, tree preservation orders, flood zone
• Look at what neighbours have built — check the council’s planning portal for approved applications in your street
• Talk to your neighbours early — especially if your extension will be near their boundary

• Choose your design professional — architect, architectural technologist, or building designer
• Brief them clearly — what you want, what your budget is, and any constraints
• Review initial design options — consider layout, light, flow, and how the extension connects to existing rooms
• Finalise the design — agree on the final layout, dimensions, and appearance
• Confirm whether planning permission is needed based on the final design
• Get planning drawings prepared (if planning permission needed)
• Get building regulations drawings prepared

These can run in parallel to save time.

• Submit planning application (if needed) — £548, 8-week decision period (guide)
• Apply for an LDC (if building under PD) — £274
• Appoint a structural engineer — provide the architect’s drawings
• Receive structural calculations and drawings — typically 1–3 weeks
• Submit building regulations application — Building Notice or Full Plans
• Serve party wall notices — at least 1–2 months before work starts
• Wait for party wall responses — 14 days for neighbour to respond
• Appoint party wall surveyor if neighbour dissents — allow 4–8 weeks for the award

• Prepare a clear specification — what is included, what is excluded, materials, finishes
• Get at least 3 quotes from builders — provide the same drawings and specification to each
• Check references — visit previous projects if possible
• Verify insurance — public liability (min £2m) and employers’ liability
• Check for memberships — Federation of Master Builders, TrustMark, or similar
• Compare quotes carefully — cheapest is not always best
• Agree a written contract — scope, price, payment schedule, start date, estimated completion
• Agree a payment schedule — never pay more than 10–15% upfront. Stage payments tied to milestones.

• Confirm all approvals are in place — planning, building regs, party wall
• Confirm builder’s start date and estimated timeline
• Notify building control of commencement date
• Notify your buildings insurer about the planned work
• Arrange skip hire and check if a licence is needed
• Arrange scaffolding and check if a pavement licence is needed
• Clear the work area — move furniture, plants, and garden features
• Set up temporary kitchen if needed
• Agree working hours with builder and inform neighbours
• Check for underground services — request utility maps before any digging

• All approvals received
• Party wall process complete
• Builder contracted and insured
• Building control notified
• Site cleared and accessible
• Payment schedule agreed
• Neighbours informed

You are ready to build.