If you’re planning a house extension, one of the first things you’ll likely want to know is: how long do house extensions take? It’s a fair question, and the answer can be the difference between smooth sailing and a stressful build.
While there’s no one-size-fits-all answer, this guide gives you a realistic look at the timeline—step by step—from your first sketch to moving into your brand-new space. Whether you’re thinking about a single-storey kitchen extension or a full wraparound project, here’s everything you need to know.
What Affects How Long a House Extension Takes?
Several factors influence the timeline of a house extension. Here’s what typically impacts how long your project will take:
- Type of Extension: A single-storey extension is quicker than a double-storey or a wraparound. The more complex, the longer the build.
- Planning Permission: Not all extensions need it, but if yours does, allow 8–10 weeks for approval.
- Design Complexity: Open-plan spaces with structural steel, bi-fold doors, or custom finishes take more time.
- Site Conditions: Sloping land, poor drainage, or access issues can slow down your groundwork.
- Time of Year: Bad weather can delay outdoor tasks like roofing and rendering.
- Availability of Trades and Materials: Shortages or waiting on contractors can add weeks to your schedule.
Being aware of these variables from the start helps you plan better—and keeps your expectations grounded.
Average Build Times by Extension Type
Let’s break down typical construction durations for different kinds of extensions:
- Single-Storey Rear Extension: 8–12 weeks. Straightforward and popular, these are usually the fastest.
- Double-Storey Extension: 16–24 weeks. Building upwards adds complexity, especially with structural requirements.
- Side Return Extension: 12–16 weeks. Narrow and tucked away, they can be fiddly but effective.
- Wraparound Extension: 20–28 weeks. These merge rear and side returns—expect more time for structural work and integration.
- Loft Conversion: 6–10 weeks. Fast if access is easy and the structure supports it.
These estimates only cover the construction phase. Planning, approvals, and design can add more time on top.
The Stages of a House Extension Timeline
To understand how long your extension might take, it’s helpful to break it down into key stages:
1. Design and Planning (4–10 weeks)
Work with an architect or designer to shape your plans. If planning permission is needed, this can extend the timeline.
2. Technical Drawings and Building Control (3–6 weeks)
Detailed drawings are submitted to Building Control. Expect back-and-forth until everything is signed off.
3. Tendering and Scheduling (2–4 weeks)
Get quotes from builders, compare timeframes, and finalise who you’re working with.
4. Construction Phase (8–28 weeks depending on project)
The build begins. This includes everything from foundations and structure to internal finishes and snagging.
5. Completion and Handover (1–2 weeks)
Final inspections, finishing touches, and any remaining paperwork before you move in.
Expect delays if weather is poor, materials are held up, or changes are made once building starts.
How to Keep Your Extension on Schedule
Want your project finished on time? Here’s how to give yourself the best shot:
- Plan early: Get your design, permissions, and trades lined up well before your ideal start date.
- Avoid last-minute changes: Mid-build design tweaks can throw off your schedule and budget.
- Use an experienced builder: Ask for timelines upfront and make sure they have a solid track record.
- Be available: Quick decisions keep things moving, especially when unexpected issues crop up.
- Build in a buffer: Add 10–15% extra time to your plan. It’ll save stress if delays pop up.
The smoother your planning, the quicker your builder can do their job.
Do You Need to Move Out During the Build?
Not necessarily, but it depends on what kind of extension you’re doing.
You might stay put if:
- The work is limited to one part of the house.
- You’ve got access to a working kitchen and bathroom.
- You’re okay living with a bit of dust and disruption.
You might need to move out if:
- The extension affects your main utilities or access.
- You’re knocking down internal walls or doing structural work.
- You have children, pets, or just want to avoid the noise.
If you can’t move out, speak to your builder about setting up a temporary kitchen or phasing the work.
Final Thoughts – Planning for Success
So, how long do house extensions take? In total, you’re looking at anywhere from 4 months to over a year—depending on what you’re building, how well you plan, and how smoothly the build goes.
The best thing you can do is prepare properly, get advice from experts, and make sure you’ve allowed enough time (and contingency budget) for the unexpected.
If you want expert guidance from a team that combines design, build, and project management all under one roof, OS Holding is ready to help. We specialise in stress-free house extensions, renovations, and new builds—delivered on time and to the highest standard. Contact us today to bring your vision to life, without the hassle.
