What is a construction programme for a house extension?

It is a time-based plan listing every phase of the build with planned and actual start and finish dates. It is the time equivalent of a budget: the budget tracks money, the programme tracks weeks, and it keeps the sequence visible so nothing stalls waiting on something that should have started earlier.

What is the difference between a construction programme and a schedule of works?

A schedule of works is a contract document listing what the builder will do and what it costs. A construction programme is a time-tracking tool that sits alongside it and shows when each phase should start and finish. You need both, and they serve different purposes.

How long does it take to start building after planning permission is granted?

Permission granted is a milestone, not a build start. Party wall notices, building control approval, and builder mobilisation typically eat several months before a digger is on site, even in a smooth project, and longer if a meter relocation or party wall dispute is involved.

Why do builders start later than the date they promise?

Start-date slip is almost always caused by the builder's previous job overrunning, with weather, illness, and subcontractor availability adding to it. It is so consistent that you should treat any quoted start date as optimistic and build a buffer into your programme from day one.

What long-lead items need ordering early on an extension?

Glazing, fitted kitchens, and utility meter relocation all carry lead times measured in weeks or months, so they must be ordered during the design or early structure phase rather than when you think you need them. Waiting until the walls are up means waiting with a half-built extension.

When is the best time of year to start an extension build?

Late spring, roughly March to May, is ideal because it gives you summer for the structure and roof and lets you reach the wet trades before the cold months. The worst case is hitting plastering and screeding in November, when drying times stretch and push every later phase back.

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Phase 2 · Pre-Construction · Task 12 of 13

Construction Programme: Building Your Schedule

Most extensions take 9-15 months from architect to sign-off. A construction programme stops you losing weeks to avoidable sequencing mistakes.

13 min readUpdated 2026Premium

Construction programme timeline infographic showing eight build phases from planning through completion, with four lead-time arrows for ordering the kitchen, ordering glazing, utility meter relocation, and the build-over agreement pointing to the phases they must precede, a weathertight-shell divider, and a builder delay buffer zone

Prerequisites

Complete these first

The most common source of stress on an extension project isn't the budget. It's the feeling that you don't know what should be happening right now, or what needs to happen next month for everything to line up.

Builders don't volunteer this information. They're thinking about their current task, not the seven things that need to happen in the right order over the coming months. That's your job, and it requires a construction programme.

What this guide covers

01What a Construction Programme Actually Is
02What Happens After Planning Permission Is Granted
03The Dependencies That Catch You Out
04Typical Phase Durations
05The Builder Start-Date Buffer
06How to Build Your Programme
07Seasonal Timing
08Using Your Programme to Communicate
09When the Programme Slips
10What Good Looks Like

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