May 22, 2025
Home extensions are among the most popular ways to add space, functionality, and value to a property. Whether you’re planning to expand your kitchen, create a new living area, or add an extra bedroom, a home extension can significantly improve your quality of life and increase the appeal of your property. However, one of the most common questions homeowners ask is: How long will my home extension take?
The truth is, the answer depends on a range of factors—from the complexity of the design to the time it takes to secure planning permission. That said, having a clear idea of the typical milestones and the timeframes associated with each phase of an extension project can help you plan effectively, set realistic expectations, and avoid unnecessary delays.
In this article, we’ll walk through the key milestones of a typical home extension, breaking down what happens at each stage and how long you can expect each part of the process to take.
Every successful home extension begins with detailed planning. This is the phase where you define what you want from the extension, consult an architect or designer, and get a rough idea of budget, materials, and layout.
During this stage, you might also begin informal conversations with your local planning authority or a planning consultant, especially if your extension is not likely to fall under permitted development rights.
2 to 6 weeks, depending on how quickly decisions are made and the availability of professionals.
Not all extensions require formal planning permission. Some fall under permitted development rights, particularly rear single-storey extensions, provided they meet specific size and height requirements. However, even if your project is permitted, obtaining a Lawful Development Certificate from your local authority is often recommended for legal clarity.
If full planning permission is needed, the process will typically involve:
Once you’ve received planning permission (or confirmation under permitted development), the next step is creating detailed technical drawings and submitting them for building regulations approval. These drawings will include structural details, energy efficiency measures, fire safety, and drainage systems.
Depending on your local authority, you can apply via:
In many cases, a structural engineer may be required to prepare calculations, especially if steel beams or complex foundations are involved.
2 to 6 weeks, depending on complexity and response times.
Before construction can begin, you’ll need to choose a contractor. This typically involves:
Avoid rushing this stage. Selecting the right builder is critical to avoiding delays, disputes, and extra costs later.
2 to 4 weeks, depending on builder availability and your own decision-making speed.
With everything in place, the construction phase begins. The first task is site preparation, which includes:
This is followed by groundworks, which often involve:
Factors such as soil conditions, site access, and weather can all influence how long this stage takes.
2 to 4 weeks for straightforward projects
The superstructure refers to the walls, roof, and external structure of your extension. This is where your vision begins to take physical form.
Tasks include:
At this stage, your extension should become weather-tight, meaning it can withstand the elements, allowing interior work to begin.
4 to 8 weeks, depending on size and design complexity
The first fix includes all the internal systems that go into the building before plastering begins. This includes:
This phase needs to be coordinated with various trades, including electricians, plumbers, and heating engineers.
2 to 3 weeks
Once the first fix is complete and building control has inspected the work, the walls and ceilings can be plastered. Drying time will vary depending on the season and ventilation, and no further finishing should be done until plaster is fully dry.
This phase covers the finishing touches:
Second fix usually moves faster than first fix, but the quality of finish is critical at this stage.
2 to 3 weeks
Before the extension is fully complete, you’ll walk through the space with your builder to identify any snagging issues. These might include:
You’ll also need a final inspection from building control to receive your completion certificate, which is essential for insurance and potential resale.
Estimated time:
1 to 2 weeks
Not necessarily. Many extensions fall under permitted development rights, especially smaller single-storey rear extensions. However, it’s wise to check with your local authority and obtain a lawful development certificate for peace of mind.
In most cases, yes—especially for single-storey extensions. However, expect noise, dust, and limited access to parts of your home. Some people choose to move out temporarily during the more disruptive phases.
Common causes of delay include poor weather, planning permission complications, late material deliveries, changes to design mid-build, and lack of contractor availability. Good planning and communication are essential to stay on track.
If your extension affects a party wall, you’ll need to serve a Party Wall Notice at least two months before work begins. General courtesy and early conversations with neighbours are always recommended, even if not legally required.
Yes, but expect possible delays due to shorter daylight hours and adverse weather. Some stages, like groundwork or roof construction, are more weather-dependent and may be affected.
Yes. Once the work is finished and signed off by building control, you’ll receive a completion certificate. It’s vital for future property sales, mortgage applications, and insurance purposes.
Building a home extension is a significant investment of time, money, and energy—but when carefully planned, the rewards can be substantial. Understanding the key milestones and the expected timelines at each stage can help you make informed decisions, manage your budget, and minimise disruption.
While every extension is unique, a realistic timeframe for a standard home extension ranges between 3.5 to 6 months, from concept to completion. By working with experienced professionals, keeping communication open, and preparing for each phase, you’ll be well on your way to a successful home upgrade.
If you're about to start your own extension project, remember: clear timelines, thorough planning, and attention to detail are just as important as bricks and mortar.
If you’re planning a renovation, extension, or full home transformation, visit our website Milkov & Son Construction to explore our expert services and recent projects. Take the first step toward creating your dream space by contacting us online or calling +44 7951 625853.
