How Long Do Home Extensions Take?

Home extension timelines vary depending on design, planning permission, engineering checks and the build method itself. In most cases, the full process takes several months—and sometimes up to a year—from concept to completion.

One of the most common questions asked about home extensions is: how long will it take? The answer depends on a range of factors including design complexity, materials and even the weather. However, there are some general expectations for each stage of the process.

The design process

Design can take anywhere from two weeks to two months, depending on complexity.

The first step in creating an extension is the design phase—either with an architect or through a simpler process if you’re using a timber frame extension kit. Architects will measure your property, prepare plans, and make revisions as needed. This stage typically takes between 2 weeks and 2 months.

Planning permission

With your plans ready, you can determine whether planning permission is required. If not, you can progress immediately. If it is needed, expect an additional 6–8 weeks for approval. If declined, you’ll need to amend the plans or appeal the decision.

Building approval

Once planning permission is secured (or confirmed as unnecessary), the next phase involves technical design and building control approval. A structural engineer assesses foundations, beams, roofing and other key components. This typically adds around 1 month.

Party wall notices

If your project affects shared boundaries or walls, you will need to issue party wall notices to neighbours. Speaking with them beforehand often speeds up the process.

The building process

Actual construction time varies depending on materials and the project type. Timber frame extensions are typically faster, while brick or block structures take longer. In general:

Altogether, from planning to completion, an extension can take up to 12 months. Some stages can be sped up, while others—like weather delays or planning decisions—are outside your control. Understanding the timeline helps set realistic expectations and minimises disruption.