This is usually one of the first questions after cost, and the honest answer is that it depends heavily on scope, but most homeowners underestimate the time needed before building work even starts, and overestimate how quickly the finishing stages go.
Before Anything Is Built
- Design and planning application: 4 to 10 weeks, depending on complexity and whether pre-application advice is sought
- Planning decision: up to 8 weeks for a standard application, longer if the council requests amendments or the application is called in for committee review
- Building regulations approval and structural engineer input: can run alongside planning, typically 2 to 4 weeks once designs are finalised
- Booking trades and ordering long-lead items, such as bespoke windows or structural steel, can add several more weeks before the first spade goes in the ground
In total, it is common for six months or more to pass between the first conversation and the start of on-site work, particularly for anything beyond a simple permitted development project.
Typical On-Site Timelines
- Single-storey rear extension (20 to 30 square metres): 8 to 14 weeks
- Double-storey extension: 14 to 20 weeks
- Kitchen extension including full open-plan conversion: 10 to 16 weeks
- Loft conversion: 6 to 10 weeks
These figures assume no major unforeseen issues, reasonable weather during weather-sensitive stages, and no delays sourcing materials or trades.
What Actually Causes Delays
- Late decisions on fittings, such as kitchen units or bathroom suites ordered after the point they were needed on site, holding up subsequent trades
- Discoveries once walls are opened up, particularly in older properties, such as unexpected wiring, damp, or foundations that do not match original drawings
- Weather during roof-off periods or external finishing stages
- Poor sequencing, where trades are not booked in the right order and end up waiting on each other
How We Keep Projects on Schedule
- A single project manager coordinating every trade against one schedule, rather than the client having to chase separate contractors
- Materials and fittings ordered against a schedule, with decisions flagged to the client well before they become urgent
- Realistic timelines quoted from the outset, including the pre-construction stages most builders leave out of their estimate
If you want an honest, realistic timeline for your specific project rather than an optimistic one designed to win the job, get in touch and we will walk you through it stage by stage.