Trades Around
Renovation timeline planner · 2026

How long will your single-storey rear extension actually take?

A rear addition on the ground floor — typically a kitchen-diner, family room or extended living space. Build on site is usually 12–16 weeks for a 20–30 m² extension, but the full project from design to handover runs 9–12 months once you factor in drawings, planning, building regs, tender and steel/glazing lead times.

Sources cited per phaseNo email gateUpdated quarterly
The plan

Single-Storey Rear Extension

A rear addition on the ground floor — typically a kitchen-diner, family room or extended living space. Build on site is usually 12–16 weeks for a 20–30 m² extension, but the full project from design to handover runs 9–12 months once you factor in drawings, planning, building regs, tender and steel/glazing lead times.

Tell us about itLive updates — no submit button.
Scope
Standard 20–30 m² (permitted dev, single knock-through)
Planning route
Permitted dev (Lawful Dev Cert)
Knock through?
No — keep separate
Glazing
Standard windows & door
Week-by-week

Your timeline

Hover any bar for the trade detail · scroll horizontally on small screens
Phase
W-27
W-25
W-23
W-21
W-19
W-17
W-15
W-13
W-11
W-9
W-7
W-5
W-3
W-1
DAY 1
W1
W3
W5
W7
W9
W11
W13
W15
W17
Pre-construction · before day 1
Engage architect — concept design
Submit planning application
Submit Lawful Development Certificate
Submit Prior Approval (Larger Home)
Structural engineer drawings
Submit Building Regs Full Plans
Tender — get 3+ quotes
Party wall notice
Order bifolds / sliding doors / roof lantern
Confirm builder & sign contract
Steel beams (RSJ) for fabrication
Order bricks/blocks to match existing
Skip & scaffolding licence
On site · from day 1
Site setup & strip-out
Excavation & footings
Drainage, DPC & oversite
Floor slab & insulation
Blockwork & cavity walls to wall plate
Steel installation (knock-through opening)
Roof structure
Roof covering
Windows, bifolds, doors & rooflights
First-fix plumbing & heating
First-fix electrics
Internal stud walls & insulation
Plasterboard & plastering
Floor finish
Second-fix plumbing & electrics
Decoration & external works
Building control sign-off & handover
On-site trade workRegulatory / professionalDecision deadline (you act)Contractor prep / lead time
On-site total
15.7–16.3 weeks

On-site only. Add ~26 weeks of pre-construction (planning, ordering, lead times) before day 1.

Reality check

Where it tends to slip

If your project goes long, it’ll usually be one of these. Worth knowing before you sign anything.

01Bad weather during groundworks — heavy rain in winter floods trenches, frost stops concrete pours; can add 1–3 weeks to early phases.
02Hidden ground conditions — tree roots, made-up ground, old drains or crumbling boundary footings forcing deeper or piled foundations (2–4 weeks).
03Bifold doors or roof lantern arriving late — typically 6–12 weeks lead, and the build can't go fully watertight until they're in.
04Steel fabrication backlog — 2–3 weeks is typical but can stretch in busy spring/summer windows.
05Building control inspection scheduling — site can sit waiting for the inspector at foundations, drains, steel and pre-plaster sign-offs.
06Party wall surveyor disputes — formal awards can delay start by 4–8 weeks if neighbours dissent.
When you’re ready

Trades you’ll need

All listed on TradesAround. No paid placements, no sponsored bumps.

Ready to get quotes?

Find local trades on TradesAround.

Browse the directory