Extensions are exciting. They promise more space, better light, and a home that finally works the way you want it to. But they also take time. And often, more time than people expect.
In this guide, we’ll walk you through the real timeline of a typical house extension — from those first conversations with an architect all the way to the day you move back in.
📅 The Full Timeline at a Glance
Here’s a rough idea of how long each stage typically takes:
| Stage | Time Estimate |
| Feasibility & Ideas | 3 – 12 months |
| Design & Planning | 2–4 months |
| Permissions & Approvals | 2–3 months |
| Tendering & Contractor Choice | 1–2 months |
| Construction | 3–6 months |
| Snagging & Move-in | 1 month |
Total Time: If you exclude the feasibility/ Ideas stage, you’re looking at Roughly 9–16 months from getting first designs to finished home – and that’s if everything goes smoothly!
🔍 A Stage-by-Stage Breakdown
💡 Feasibility & Ideas (3 – 12 months)
Before you ever speak to an architect or builder, there’s usually a long period of thinking, talking, Googling, and second-guessing.
This is the “what are we actually doing?” stage — and for most homeowners, it takes anywhere from a few months to over a year to feel ready to move forward.
This phase often includes:
- Walking around the house with a tape measure (again)
- Saving Pinterest images and following #kitchenextension on Instagram
- Asking friends, neighbours, and local Facebook groups what they did
- Sketching layouts on the back of envelopes
- Talking (and talking) with your partner about whether it’s worth it
- Getting a rough ballpark figure from a builder or architect — and then rethinking everything
This is a hugely important part of the process, even though nothing “official” is happening yet. It’s when you begin to:
- Get clarity on your priorities (space, light, layout, future-proofing)
- Figure out what you can afford and what might need to wait
- Understand what’s possible within your site, your budget, and your council’s rules
👉 Tip: If you’re stuck in this stage, a short consultation with an architect or renovation expert can be incredibly helpful. They won’t draw up full plans, but they can give you a sanity check on what’s feasible — and what’s not worth chasing.
✏️ Design & Planning (2–4 months)
This phase sets the tone for your whole project. It involves:
- Meeting with your architect or designer
- Talking through your needs and budget
- Developing initial sketches and refining the design
- Getting rough costings so you know what’s realistic
The more decisive and communicative you are during this phase, the quicker it moves. But rushed decisions now can cause expensive delays later.
📄 Permissions & Approvals (2–3 months)
Even if your extension falls under Permitted Development, you’ll likely still need:
- A Lawful Development Certificate
- Building Control approval
- Possibly Party Wall Agreements with neighbours
If full planning permission is required, factor in 8 weeks minimum for a decision — longer if revisions or appeals are needed.
👷♂️ Tendering & Contractor Selection (1–2 months)
This stage is often underestimated. You’ll need time to:
- Prepare tender documents (your architect can help)
- Get 2–3 quotes from builders
- Compare like-for-like and ask questions
- Negotiate terms and choose your contractor
A good contractor is usually booked up for months in advance — so locking someone in early is a smart move.
🛠 Construction (3–6 months)
This is the most visible part of the process — and the one most people think of when they imagine an “extension.” Typical phases include:
- Site set-up, demolition, and foundations
- Structural work and shell construction
- First fix (electrics, plumbing), then second fix (fittings, plaster)
- Kitchen/bathroom install and decorating
Things that can delay this stage:
- Poor weather (especially for roof or foundation work)
- Delays in materials arriving
- Unforeseen issues (like discovering a hidden manhole or rotten joists)
- Late decisions about finishes or fittings
🏡 Snagging & Moving Back In (1 month)
Once the build is “done,” there’s still a bit to go:
- Checking for minor issues (snagging) and getting them fixed
- Deep cleaning, decorating, and finishing touches
- Final sign-off from building control
- Moving furniture in and making the space your own
⚠️ What Affects Your Timeline?
No two projects are exactly the same. Some of the biggest factors that affect timing include:
- Complexity of the design (a kitchen extension is quicker than a double-storey wraparound)
- Your availability to make decisions quickly
- Planning delays, especially in conservation areas
- Lead times on windows, doors, kitchens, and fittings
- Builder availability (good ones book up early)
- Unexpected problems uncovered during the build
✅ Tips to Keep Things Moving
While you can’t control everything, here are a few ways to avoid unnecessary delays:
- Start early — even if you don’t plan to build until next year
- Be decisive — make choices on layouts, fittings and finishes as early as possible
- Use professionals who specialise in domestic work — they understand the flow and pitfalls
- Communicate regularly with your team — and don’t be afraid to ask questions
🏠 Real Talk: Is It Worth It?
Yes. The time, effort, and dust are worth it — if you go in with your eyes open. Many homeowners say the key to surviving a renovation is managing your expectations, especially around time and budget.
Plan for delays, give yourself breathing room, and don’t assume it will all go like a TV makeover show. Real homes take time — but when it’s done right, it’s worth every minute.
So, how long does a house extension really take?
In most cases, around 9 to 12 months from getting those first drawings to final sign-off — longer if it’s a complex build or decisions drag on.
If you’re planning one, the best thing you can do is start early, ask lots of questions, and stay realistic. Your future self — enjoying coffee in your light-filled new kitchen — will thank you for it.
