How long does an extension take?

Key Takeaways

• Hiring experienced professionals early can save you a lot of time, stress and costly mistakes throughout your extension journey.   
• Consultation with your architects or extension specialists can help you understand your project scope before you commit. 
• Proper planning and open communication are key to keeping your extension on schedule. 
• Delays are normal; weather, planning permission and design changes can all impact how long an extension can take. 

So, you are dreaming of more rooms: a bright new kitchen, a sunny family hub, or an extra bedroom for growing needs. It’s exciting for sure, but you might be asking in equal measures, “How long does it take to build an extension?” That’s totally natural. We’ve all been there: staring at dusty rooms and imagining a bigger, lighter home. 

On average a full house extension journey takes anywhere from 6 to 16 months, depending on your project. But more commonly in the UK, homeowners see timelines of around 7 to 12 months  for a standard build, longer for complex or double-storey additions.  

How Long Does Each Stage of an Extension Take?

Every house extension begins with a dream and a dozen questions. 

Where do we start? Who should we speak to? How long before we can actually break ground? Whether you are planning a cosy kitchen extension or a full double-storey upgrade, understanding the key phases helps you take control of the timeline and your expectations. 

Here’s a real-world look at how long each stage of an extension takes, from initial ideas to contractor handshakes. 

• Preparation & brief (1-5 weeks)

You have made the decision, you want more space. Maybe your kitchen feels too narrow, or your kids need their own rooms. Whatever the reason, this is the exciting first step. You will meet with an architect  or designer to talk through your ideas, needs, and budget. These first conversations are full of energy.

You’ll start imagining where the new wall might go or how much sunlight you want in your dining area. 

Here’s what usually happens: 

• Week 1-2: You meet the architects, walk around the house, and discuss your ideas.   
• Week 3-5: The architects create an outline plan based on your needs. They’ll also let you know “how long does it take to get planning permission for an extension, or if your extension can be done under permitted development. 

Well, let’s discuss an example of a couple in Leeds here for a better understanding, they wanted a kitchen layout because they couldn’t agree on where to put the fridge! It’s normal__this stage is about exploring all the options. 

This part usually takes 1 to 5 weeks, depending on how clear your ideas are and how quickly you make decisions.   

• Design & technical drawings (2-8 weeks)

Now it’s time to turn your ideas into proper plans. 

Once you are happy with the general layout, the architect starts drawing detailed designs. These are the actual building plans your builder will follow. 

What happens: 

• First, you will get some simple layout ideas, like where the walls, windows, and doors will go. 
• Then, you’ll make a few changes together. 
• After that, the architects create technical drawings. These are more detailed and meet building regulations. 

A homeowner in Birmingham didn’t realise their island unit in the kitchen would block a door. The architect noticed it early on in the drawings, and they adjusted the layouts to make it work.

This stage can take 2 to 4 weeks for simple extensions. But if your project is big or has tricky details– like unusual roofs or if you are in a conservation area it might take 6 to 8 weeks. 

• Planning permission / PD / Party wall notices 

This is where things slow down a bit, but it’s an important step. 

Depending on what kind of extension you’re doing, you might need planning permission from the council, or you might be able to build under permitted development rules. 

• If your project follows the permitted development rules, you won’t need full planning permission , but most people still apply for a lawful development certificate (LDC) which takes up to 8 weeks. 
• If you do need planning permission, it usually takes 8 to 12 weeks and sometimes longer, if there are objections or the council asks for changes. 

We met a family in Croydon who applied for planning in May. Their neighbour complained about losing light, so the council asked for changes. The final approval didn’t come through until August, adding three extra months to the time light. 

What about partywall? 

If your extension is close to a neighbour’s wall or boundary, you might need to send them a party wall notice. If they agree, you can move forward. If they don’t, you’ll need to bring in a surveyor, which could take another 4 to 8 weeks. 

This whole process including planning and party wall agreement which can take anywhere from 8 to 16 weeks or more.  It’s one of the most common reasons for delays in building extensions. 

• Pre-construction & tendering (3-6 weeks)

Time to choose your builder and get ready to start building. 

After you’ve got your planning approval and final drawings, you’ll start looking for a builder to do the work. You’ll send your plans to a few contractors to get quotes (this is called “tendering”). 

What happens: 

• Builders visit the site, ask questions, and send you a price. 
• You compare quotes, check references, and choose the right team. 
• Once chosen, you’ll sign a contract, agree on the schedule, and set a start date. 

Why don’t you share a real story with you guys? A family in Brighton got three quotes, one was £70,000, another £85,000, and the last one was £110,000! They chose the middle option, because the builder had great reviews and a clear timeline. This stage normally takes 3 to 6 weeks: 

• 3 to 4 weeks to get and compare quotes. 
• 1 to 2 weeks to confirm the builder and get everything signed.

Make sure you take your time choosing a builder  you trust, it makes a huge difference to the whole experience. 

Time frame for each type of extension

Every home tells a different story.

Some need a little more space to grow, others want to open up the heart of their home. No matter the goal, the type of extension you choose will have a big impact on how long the journey takes.

Below, let’s break down the most common types of home extensions, exploring realistic timelines, emotional considerations, and what life might look like while the work is underway. 

• Simple single-storey extension

Time frame: 3-4 months for construction| 6-9 months total 

A single-storey rear or side extension is one of the most common choices from homeowners and often the fastest to build. But “simple” doesn’t always mean easy. 

In most cases, from planning to completion, the whole process takes around 6 to 9 months, with the actual build taking about 12 to 16 weeks. You will go through design, approvals, groundworks, wall constructions, roofings, and then the finishing touches.  

• Kitchen extension

Time frame: 4-6 months for construction|8 to 12 months total

There’s something deeply emotional about a kitchen extension. The place where you can create unforgettable memories, bake birthday cakes, do homework supervised, and share evening cups of tea. 

But building one? It takes time and patience. So, how long does a kitchen extension take? 

From the first drawing to the final tile being laid,  kitchen extension often spans 8 to 12 months. The construction alone, foundations, walls, electrics, plumbing, kitchen installation can take 4 to 6 months, depending on complexity. 

What slows things down? Waiting on bespoke kitchen units, sourcing materials like quartz countertops or large rooflights and fitting everything with precision. 

“We didn’t realise how much we relied on the kitchen until we didn’t have one. But now, standing in that bright open space, it’s more than just a kitchen. It’s the soul of our home.” –Karim, Brighton   

• Wrap-around / L-shaped extension

Time Frame: 5-7 months for construction | 10-14 months total 

These extensions completely transform a home, especially older Victorian or Edwardian layouts that feel dark or boxed in. a wrap around or L-shaped  extension opens things up, letting light flood in and creating true open-plan living. 

But with big dreams comes big work. These projects usually need: 

• Extensive groundwork
• Structural steel beams for support 
• Complex roofing transitions 
• Utility re-routing 
• Planning permission and sometimes party wall agreements

That’s why they often take 10 to 14 months from start to finish. The build phase alone is around 5 to 7 months. 

• Double storey extension 

Time Frame: 6-12 months for construction | 12-16+ months totally 

A double-storey extension is the most time-intensive of them all– and understandably so. You’re adding space both upstairs and down, meaning more material, more planning, more labour, and more complexity.  

The full timeline can range from 12 to 16 months, sometimes even longer, spending on: 

• Whether planning permissions are required
• Structural changes to the existing home
• Weather delays 
• Availability of specialist trades (plasterers, joiners, tilers)

The build phase alone often takes 6 to 12 months, especially if it involves bathrooms, bedrooms, or bespoke fittings. 

A Quick Glance At Timelines 

Tips for keeping your extension on schedule

There’s no sugar-coating it: building an extension is a journey, often a long one. 

You’ll have days filled with excitement and others full of dust, noise, and delays. But with the right mindset and a few proactive steps, you can keep your build on track, and protect your peace of mind.

These tips aren’t just about saving time. They’re about reducing stress, avoiding costly mistakes, and making your home extension experience feel more rewarding than overwhelming. 

• Find trusted pros early

Start by surrounding yourself with the right people like architects, builders, and surveyors who’ve actually delivered the kind of extension you’re planning. A well-matched team will not only help you avoid delays but guide you through every twist and turn. 

Look for: 

• Portfolios with similar extensions (kitchens, side return, wrap around)
• Local experience (they’ll know your council’s planning quirks)
• Glowing reviews from other homeowners like you.  

The earlier you involve your professionals, the smoother your journey becomes. 

• Be emotionally prepared 

Let’s be honest, living through an extension isn’t easy. 

The kids may be doing homework in the living room while the kitchen’s being torn down. There might be early morning hammerings or weeks where your favourite mug’s buried under dust. Expect emotional ups and downs , and prepare your family too. It’s okay to feel stressed and impatient. What helps? 

• Clear routine 
• Honest conversations about progress
• Celebrating small wins 

It’s not just about the build, it’s about adapting while holding on to your vision of the end result.  

• Lock decisions early

Changing your mind during construction is one of the fastest ways to lose time and money. 

Maybe it’s switching tiles or deciding to knock down an extra wall once the structure’s up. These delays can cascade. Materials may need recording. Tradespeople might get rescheduled. It adds up fast. 

So, what can you do? 

• Finalise finishes, colours, fittings and layouts before the build begins. 
• Stick to your plan as closely as possible. 
• If you do need to change something, communicate early. 

Even seemingly small tweaks can have a knock-on effect on trades, plumbing, and even inspections.   

• Order bespoke items early

We’ve seen it countless times, beautiful glass doors held up by a 10-week lead time, or a custom kitchen arriving late, leaving builders stuck. 

If your design includes made-to-order or imported features, order them early. Think; 

• Sliding or bi-fold doors 
• Bespoke kitchen units or worktops 
• Large windows, roof lights 
• Specialist bathroom fittings 
• Structural steel for open-plan layouts

Talk with your architect or project manager about timelines. You don’t want builders standing idle waiting for deliveries.  

• Plan for weather downtime 

In the UK, even a week of heavy rain can bring your schedule to a halt, especially during groundwork or bricklaying. 

Don’t be caught off guard: 

• Builds starting in autumn/winter may face extra weather delays
• Frost, high winds or storms can halt roofing and scaffolding work
• Brickwork needs dry, mild weather to set properly

Your builders can work around some weather, but not all. If time is tight, start your projection spring or early summer when conditions are more predictable. 

• Maintain open communication 

The best way to prevent misunderstandings? Keep the conversation flowing. 

Weekly site meetings, even quick ones can make a huge difference. It keeps everyone accountable, ensures progress is on track,and gives you space to raise concerns or ask questions. 

You don’t have to know technical jargon. Just be honest about what’s worrying you or what doesn’t feel right. Most builders appreciate a homeowner who’s engaged but respectful. You are working together toward the same goal: your dream space.  

• Set a buffer contingency

No matter how well you plan, surprises happen. 

• A buried pipe where foundations should go
• Unexpected planning delays
• Supplier issues of price changes mid-build

That’s why every expert recommends setting aside an extra 10-20% of your time and budget. It’s not a luxury, it’s essential. This buffer gives you breathing room if something goes sideways and helps keep the stress levels down when it does. Think of it as emotional insurance for your sanity.  

• Consider temporary relocation 

If your extension affects major living areas, like the kitchen or bathroom, staying at home during the build can wear you down fast. 

Imagine: 

• No running water while tiling is done 
• Cooking on a single plug-in hob with kids screaming 
• Living in a bedroom while the rest of the house is torn apart