How Long Does a House Extension Take? Typical Phases and What Affects the Programme

People often ask how long an extension will take. The honest answer is that it depends on the size and complexity of the project, but it helps to know the phases and where time tends to go.

Before work starts on site

• Design and survey: developing the brief, drawings and structural input

• Planning or permitted development: householder applications are usually determined within eight weeks, but preparation and any additional information can add time

• Building Regulations approval and technical drawings

• Party wall notices, where relevant

• Tender, programme and ordering long lead-time items

On site

• Setting out, groundworks and foundations

• Structure and any steel needed to open up the existing house

• Roof and weathertight shell

• First fix, plastering and drying time

• Kitchen, second fix, decoration and snagging

What can lengthen the programme

• Unexpected ground conditions or drainage found when digging

• Changes to design or finishes during the build

• Delays to deliveries of windows, doors, steel or kitchens

• Bad weather during groundworks and roofing

• Waiting for inspections or approvals from third parties

What can shorten it

• Finalising design and finishes before starting

• Ordering lead-time items early

• Clear decision-making during the project

• A single team coordinating design, engineering and construction

Plan for living through it

Think about how you will use the kitchen, bathrooms and garden during works. Discussing access, working hours and temporary arrangements early makes the process easier for everyone.

Find out more about our house extensions service.

Thinking about a project in London? Get in touch with Tota Design & Build to talk it through.