The homeowner’s ultimate guide to house extensions in the UK

The homeowner’s ultimate guide to house extensions in the UK Conversions & Extensions

If you’re thinking about extending your home, it can be difficult to understand where to start. Extending your home can be a game-changer, providing more space for a growing family and significantly boosting your property’s value. Whether it’s adding a light-filled kitchen diner, a modern home office, or an extra bedroom, each project comes with its own set of considerations—from the initial design to the finishing touches.

In this guide, we’ll explore various extension types to suit different homes, look into inspiring design ideas for your living space, and provide practical advice on managing costs and design project timelines. We’ll also help you understand the essentials of planning permissions and building regulations to ensure your extension project runs as smooth as possible.

Take a look at the below and learn about all you need to know when extending your house, ensuring you make informed decisions every step of the way. Whether you’re looking to extend up, out, or sideways, understanding the process helps you achieve the best results for your living space.


What is a home extension?

A home extension is a construction project where you add space to your existing property. During an extension, homeowners can create new rooms or enlarge current ones. Home extensions can be done in many different ways. Some projects extend homes upwards, adding another storey or outwards to extend into the garden, or sideways stretching into unused side return space.

What isn’t classified as an extension?

Internal alterations within the existing walls of the house, loft or basement conversions, or simply refurbishments without structural alterations, don’t typically count as extensions. Similarly, adding a conservatory may sometimes be considered an extension, but because they usually involve different construction methods and materials, they are often classified separately.

What is the goal of home extensions?

When planning a home extension, you still want to do the extension in line with the style and functionality of the rest of your home, without the need to relocate. Extensions offer a practical solution to space issues and can be used for anything from new kitchens or dining areas to additional bedrooms or even a home office.

A home extension provides valuable extra space and can be a smart investment, significantly increasing the functionality and potential value of your home.


The different types of house extensions

Deciding on the type of house extension can shape the way you live in your home. Each type has its benefits and can meet custom requirements of homeowners, whether it’s gaining an extra bedroom or building your ideal kitchen space.

Single and double-storey extensions

A single-storey extension usually involves expanding the ground floor into the surrounding areas. This extension method may be used for a larger kitchen, a new dining area, or additional living space that opens out to the garden. It’s less about adding bedrooms and more about enhancing the living areas you use daily.

On the other hand, a double-storey extension adds space across two floors. This could give you extra bedrooms upstairs and more living space on the ground floor.

Front, side, and rear extensions

Front extensions alter the face of your house and can add curb appeal along with additional living space. However, they often come under tighter planning scrutiny as they change the street view.

Side extensions are a smart way to use a house’s often-neglected side profile. They can blend with the design of your existing home or make a bold modern statement.

Rear extensions expand out into the garden and are among the most common types. They’re ideal for creating large open-plan areas that connect indoor and outdoor spaces, perfect for modern family living and entertaining.

Special types: dormer and terraced house extensions

Dormer extensions are generally associated with loft conversions. They protrude from the slope of the roof and can add headroom to a loft, transforming it into a fully functional space like a bedroom or study.

Terraced house extensions require careful consideration as their impact on neighbours and the potential for planning restrictions are more profound than other extensions. Yet, even with a terraced home, a well-designed rear or side return extension can add considerable space.

The best type of extension for your home will depend on your property, your needs, and sometimes, your neighbours’ considerations and concerns surrounding the extension. It’s essential to weigh up the benefits of each against practicalities like cost, planning regulations, and prepare for any potential disruption during construction.


Understanding house extension costs

Planning a house extension brings its fair share of financial factors into play, throughout the project. The below are some of the factors you can expect to encounter during your extension project, laid out for you so you’re not caught by surprise when the bills start rolling in.

How much does a house extension cost?

Costs for house extensions in the UK can stretch across a broad spectrum. A simple, no-frills extension might start from a more modest sum per square metre. However, for those dreaming of bespoke finishes, top-of-the-range kitchen fittings, or bi-folding doors that lead to a garden, the investment will be significantly more. Location will also greatly influence the price. A house extension in a city like London could cost more than in other parts of the country due to higher labour and material costs as well as more logistical planning required for moving materials and constructing in small spaces.

Budgeting for your house extension

The details count when it comes to setting a budget for your extension. The architecture, whether you’re planning a single or double-storey extension, the materials you choose, and whether you’re updating a semi-detached house, or a terraced home needs to be considered in your extension budget. There are also behind-the-scenes costs that need to be considered such as surveys, any necessary structural calculations, and even the type of soil upon which the property sits can all sway the final figure. Once you reach the final figure, you also need to leave a margin of around 10-20% to ensure you’re prepared for the unexpected, keeping your project afloat even when surprise costs arise.

With clear, careful planning and a realistic budget that considers every angle, your house extension can be a smooth journey to a more spacious, valuable home.

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Understanding house extension timelines

Mapping out the timeline for a house extension is as important as the design itself. A clear project plan with realistic milestones helps manage expectations and ensures your project stays on track.

The step-by-step process of extending a house

The journey of creating a house extension generally begins with ideation, followed by design and planning. Once you’ve secured the necessary permissions and finalised your design with a professional, you’ll move into the construction phase. After the build, there’s the fit-out stage where your extension truly comes to life.

Typically, the process involves:

  • Initial consultation and design (1-2 months)
  • Planning permission if required(8 weeks for decision post-submission)
  • Detailed drawings and building regulations (1-2 months)
  • Construction (variable, from 3 months onwards)
  • Interior fitting and finishing (1-2 months)

Typical timelines and potential delays

A single-storey extension might take less time to complete than a double-storey. While a simpler design could be finished within a few months, more complex projects could take over a year to be fully completed. When you’re laying out your timeline, you need to leave room for delays due to weather conditions, supply chain issues, or unexpected findings during construction, like unstable ground or previous, unrecorded building work.

What to expect during the extension process

Patience is key. You may encounter hiccups like planning rejections or revisions, the need for party wall agreements with neighbours, or site access issues. Regular communication with your architect and builder will help you stay informed about progress and any challenges that arise so it’s important to ensure that you keep the lines of communication wide open.

Throughout the build, you also need to prepare for some disruption to your daily life as the work is carried out. However, with a reliable team and a solid plan, the inconvenience will be temporary, and the result of a more spacious and enjoyable home will be worth it.

How do you navigate planning permissions for a house extension?

Getting the right permissions is a key step in your house extension project. Knowing when you need planning permission and when you don’t is crucial for a smooth process.

When do you need planning permission for a house extension?

Planning permission is required when you’re making a significant change to your home, like adding a large extension that increases the overall footprint beyond certain limits. Smaller additions often fall under ‘permitted development’ which doesn’t need formal permission, as long as they meet specific criteria like size and position. It is, however, advisable to inform possibly affected parties of any alterations being made.

How to apply for planning permission

When your extension needs permission, start by submitting detailed plans, prepared by a professional architect, to your local council. These should show how the extension will look and how it fits with your house and the surrounding area. Your council’s planning website will have guidance on the application process.

Maximising your chances of approval

To improve your chance of getting approval:

  • Follow local design guidelines to ensure your extension fits the character of the area.
  • Speak to neighbours beforehand to address any concerns.
  • Consider using a professional like an architect or planning consultant who knows what the council will be looking for and how the application process works.

Remember, every council has its own rules, so check what applies to your area. With the right approach, the planning process will be successful, and you’ll get one step closer to enjoying your new space.

Financing your home extension

Funding your house extension smartly is crucial. You have several options, each with its own benefits and things to consider.

Different ways to fund your extension

Your savings could be a straightforward way to cover costs, avoiding the need for loans or extra debt. If savings aren’t enough, a loan might be necessary for work to start. Personal loans are good for smaller amounts, while larger projects might need a remortgage or a home improvement loan. The level of funding you need will ultimately be determined by the size of your project and the current state of your savings.

Keeping your extension within budget

Staying within budget while maintaining quality comes down to detailed planning and clear communication with your builders. Getting multiple quotes, using cost-effective materials without compromising durability, and planning for possible additional costs are all practical steps to manage finances effectively.

Exploring financial options such as remortgaging, loans, and savings

Remortgaging can release equity from your home to pay for the extension. Loans can be secured against your home for the release of capital, however unsecured personal loans are also a way forward. The route you choose depends on how much you need. Using savings means you won’t incur interest, but you need to consider whether or not it leaves you with enough financial cushion.

The key is to weigh up the costs, consider the long-term implications of your funding choice, and consult with a financial adviser to find the best path for your circumstances. With careful financial planning, your dream extension can become a reality without unnecessary financial strain.

FAQs about house extensions

Here we answer some of the most common questions you might have about your home extension project.

What permissions do I need for a house extension?

Whether you need planning permission depends on the size and location of your extension. Smaller extensions often fall under permitted development, but always check with your local planning authority to be sure.

How long does a house extension take to build?

The time it takes can vary widely. A small, single-storey extension might take three to four months, while larger or more complex projects could take six months or more. Factors like weather, planning delays, and contractor schedules can also affect the timeline.

How much does a house extension cost?

Costs vary depending on size, materials, and location. A basic extension might start around £1,200 per square metre, but more complex or larger builds, especially in cities like London, could be significantly more.

Can I live in my house during the extension work?

Yes, in many cases you can, but be prepared for some disruption. If the construction is extensive, you might consider temporary accommodation to ease the stress.

Do house extensions require additional insurance?

Yes, you should update your home insurance to cover the new construction. It’s also wise to ensure that your builders have the appropriate insurance.

These answers should help you plan your extension project with more confidence. Remember, every project is unique, so it’s important to consult with professionals who can provide advice tailored to your specific circumstances.

House extensions summed up

House extensions are a fantastic way to add space and value to your home. Whether you’re looking for an extra bedroom, a larger kitchen, or a new living area, an extension can transform your living space. Remember, planning and budgeting wisely is key to a successful project. By understanding the different types of extensions, costs, timelines, and planning permissions, you can make informed decisions and enjoy a smoother process.

Partner with WindsorPatania Architecture for your home extension

Looking to extend your home with style and sustainability? Partner with WindsorPatania Architecture. We specialise in luxury and sustainable house extensions across London, Cambridge, and the rest of the UK. Our team of experts is dedicated to delivering exceptional design that perfectly fits your vision and enhances your lifestyle. Explore our Home Extension service and see how we can bring your vision to life.

By choosing us, you ensure that your house extension is not only beautifully designed but also environmentally friendly, blending seamlessly with your existing home while providing the functional space you need. Book a free call today to get started.

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