How to start a house extension UK

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Builders constructing a house extension UK

Embarking on a house extension UK, is a significant endeavour that holds the potential to transform your living space and enhance the value of your property. Yet, the journey from concept to completion can be daunting, filled with regulatory hurdles, design decisions and construction challenges.

In this home extension guide, we will take you through the essential steps necessary to initiate and navigate the process of starting a house extension in the UK. From understanding planning permissions, building regulations and planning an extension to crafting a clear vision for your extension and assembling the right team of professionals.

Whether you’re a homeowner seeking to expand your living space or an investor looking to add value to your property, this guide will serve as your roadmap to successfully begin your extension to house journey in the UK.

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Things to consider before you start your house extension UK

When it comes to house extensions in the UK, there are plenty of options available; like a garage conversion, side extension or single storey rear extension. But, all of them come with their own pros and cons, rules and regulations, so it’s important to make sure you consider all of these before committing to a build.

Please note that when looking to extend your home or planning an extension, you will need to ensure that you have all the necessary planning approval before you lay your first brick or face penalties from the local council.

Will your house extension plans add value?

Whether your house extension plans will add value to your property depends on several things, like the type and quality of the extension and current market trends. A well-designed house extension UK that complements the existing structure and meets the needs of potential buyers can significantly increase your home’s value.

Additionally, the location of your property and the current market conditions can impact the value added by an extension. You should seek the advice of a local estate agent to see if a house extension would add value to your house or not, in accordance with similar houses in your area.

If you are in a desirable area with a high demand for larger properties, an extension is more likely to increase the value of your home. However, you should also weigh up the extension costs against the property value.

Do you need planning permission for a house extension?

It depends. If you are building a house extension UK within your permitted development rights then you do not need planning permission, but, if planning an extension falls within any of the following, then your extension must have planning permission:

  • More than half of the land around the original structure is going to be covered.
  • The extension comes out forward of the front or side of the house and faces onto the road.
  • The materials used do not match the original build.
  • The extension is higher than the highest point on the roof.
  • The eaves and ridge height are higher than the existing house.
  • The eaves height is more than 3 metres, if within 2 metres of the boundary.
  • There are additional verandas, balconies or raised platforms.

Side extensions

  • More than a single-storey or over 5 metres.
  • Wider than half the width of the original house.

Rear extension single-storey

  • The extension extends beyond the rear of the original structure by over 6 metres in a semi-detached, and 8 metres in a detached house.
  • The extension is more than 4 metres in height.

Rear two-storey extension

  • The rear extension is beyond the rear of the original house by over 3 metres or is within 7 metres of the boundary opposite the rear wall.
  • The side-facing windows are not obscure-glazed and can open.
  • The roof pitch does not match the existing house.

Please note, that you cannot build a house extension UK without planning permission if you or a previous owner have extended the property previously since 1948.

What building regulations do you need?

When planning an extension, the building work will need to meet building regulations, which are put in place to protect people from insecure infrastructure.

Although you may not need planning permission for your extension, you will need building regulations approval. Unless you are adding a conservatory to your house, then you are exempt from building regulations.

To get building regulation approval, you will need to ensure your plan covers all the possible variations, including; foundations, flooring, external walls, internal walls, electrics, doors and windows, drainage and roofs.

If you are using an architect for your house extension UK, they should ensure that all building regulations are met – but make sure before you build anything.

Does your home insurance cover a house extension?

You will need to contact your home insurance provider to let them know of your building plans. The extension to house may increase the rebuild cost of your home and insurers will take this into account when pricing your home premium.

If you do not notify your insurance provider during the build, and something were to go wrong, you may find that your insurance is void. If your insurance won’t cover the new extension, then you may also need to look for a new deal.

You will also need to ensure that the builder or contractor working on your home has professional indemnity insurance to cover the costs should something go array.

Have you notified your neighbours?

It’s always a wise idea to notify your neighbours of any home improvements as they can cause disputes. If your home extension needs planning permission then the local planning authority will consult your neighbours anyway, but it’s always helpful to give them a heads up.

Also, if you share a wall with your neighbours and wish to do an extension that impacts that wall, like a loft conversion then you will need to come to an agreement, known as a party wall agreement.

How do you design a house extension UK?

Designing a house extension in the UK involves a structured process to ensure compliance with local regulations and to create a functional and aesthetically pleasing addition to your home.

Firstly, you will need to establish your requirements for the extension, considering factors like the purpose of the space, budget constraints and your desired style. Next, you’ll need to hire an architect or a designer experienced in UK building regulations and planning permissions.

They will work with you to create a design that aligns with your vision while adhering to the local guidelines.

Once you have a design concept, you’ll need to obtain planning permission from the local council if required using a building control application, ensuring that your extension complies with building regulations and doesn’t obstruct neighbours views or access to light.

After obtaining necessary approvals, you can proceed with detailed architectural drawings and structural plans. You should work hand in hand with the architect throughout this process to address any potential issues and ensure the design meets your needs and budget.

Can you draw your own plans for an extension?

Yes, you can draw your own plans for a house extension UK as long as you put the effort into learning all the building regulations and software used to create floor plans.

Saving on architectural fees could save you significant costs, especially when planning an extension. But this process can be quite time consuming, and it is always recommended that you seek professional advice where and when you can.

How big can a house extension be without planning permission?

A single-storey rear extension to house can be up to 6 metres long for terraced or semi-detached houses and up to 8 metres for detached houses without a planning application or permission.

For double-storey rear extensions, the limit is usually 3 metres from the original rear wall for terraced or semi-detached houses and 5 metres for detached houses.

However, the specific house extension rules can vary depending on the local authority, if it’s a listed building and whether the property is in a conservation area.

Is there a limit to house extensions?

Unfortunately, you can’t add extension after extension, as attached properties cannot extend beyond the rear wall of the original structure more than 3 metres, and detached properties by more than 4 metres.

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What types of home extensions are there?

In the UK, there are many different types of home extensions, some ranging in size from a small conservatory to a large two-storey wing on the property. Here are some of the different types:

Basement/cellar extensions:

Most houses in the UK will have some form of basement, usually older properties will have basements used for storage in the past. These areas can be renovated into wonderful spaces to provide entertainment or sleeping arrangements.

Rear extensions:

These house extensions are located at the rear of the property and can be single or double in height. Single storey rear extensions are usually used to amplify entertainment or leisure spaces, like a living room or kitchen extension.

Side house extension UK:

Side extensions tend to be to the side of your property and can be single or double storey in height.

Double storey side & rear extensions:

The addition of rooms to your first floor as well as the ground floor, could provide an extra bathroom and bedroom or study.

Wrap-around extensions:

Usually found to the side or rear of your property and are normally single storey.

Dormer loft extensions:

These house extensions are located to the rear of the property in a sloped roof box style.

Hip-to-Gable loft extensions:

Extension tends to alter the entire roof to add additional space, good for bedrooms and extra bathrooms.

Mansard extensions:

Altering the rear roof slope and converting it into habitable space like bedrooms and bathrooms or a study.

Additional floor extensions:

Adding an entire floor to your property while also raising the roof height an extra level.

How much does it cost to build a house extension UK?

The average cost of a house extension in the UK is around £1,500-£2,250 per metre squared of new internal space. A small single storey extension, at 30 metre squared, could range anywhere from £45,500 – £67,500 plus VAT.

How much should you budget for a house extension?

It really depends on the scale of your extension! Although the average cost for a house extension sits at around £1,500 and £2,250, this doesn’t include fitting it out with utilities and furniture which could cost significantly more depending on the style and finish you wish.

It is always best to speak to your architect or designer who will be able to tailor the budget to your own needs.

What is the cheapest way to build an extension on a house?

The cheapest way to build a house extension UK is to use a combination of cost-saving measures and being careful when planning an extension. You will need to opt for a simple and straightforward design to reduce construction costs, utilise existing structures like walls and foundations, and carry out as much DIY work as possible.

You should also consider sourcing affordable materials and finishes as well as comparing multiple quotes from contractors to help you find the most affordable contractor possible (who still upholds a high standard of workmanship and follows building regulations).

You should also consider using a design-build approach, where the same company handles both the design and construction, which can streamline the process and reduce the overall costs when adding an extension to house.

Is a house extension worth it?

Whether a house extension UK is worth it will depend on various factors including your budget, needs and long-term goals. Extensions can offer several benefits, such as creating additional living space, increasing property value and improving the functionality of your home.

If you require more space for a growing family or desire additional space for work, an extension can be a valuable investment. Moreover, a well-designed extension may also increase in property value, potentially providing a higher return on investment when you decide to sell the house.

However, it’s important to carefully consider the costs, including building, permissions and potential disruption to daily life during the building process.

What are the advantages of a house extension?

House extensions offer a variety of advantages that can enhance both your living space and property value. They can provide the opportunity to create additional room and functionality within your home, accommodating changing family needs, such as extra bedrooms, a larger kitchen or a dedicated office space.

Extensions can also improve the overall layout and flow of your home, enhancing your daily living and convenience, while also adding to its aesthetic appeal and contributing to an improved external look and kerb appeal.

House extension UK allows you to customise and modernise your home, incorporating the latest design trends and technologies, like smart home systems or triple glazing which can greatly improve the comfort and energy efficiency of a space.

This doesn’t just have to be done via technology, you could introduce more glass to the rear of a property, which could aid in warming the kitchen up in the winter.

What are the disadvantages of a house extension?

While there are a few advantages of a house extension UK, there are also potential disadvantages, the number one being cost. Cost can be a significant drawback as adding an extension to house can be expensive depending on the square footage of build and the finishes you chose.

The disruption caused during the construction process will also be a major inconvenience as it disrupts daily life and routines for an extended period, you may even need to find alternative accommodation while the build is happening which will increase the cost of the build.

Obtaining planning permission may also not be straightforward and the local council may place restrictions on what you can or cannot do with the build. And, overlooking these regulations may lead to legal issues and additional costs for adjustments in the future.

Furthermore, if the extension is poorly designed or executed, it may not blend well with the existing structure and potentially impact the overall appearance and negatively affect its property value.

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Tom is a Digital Content Writer passionate about sustainable property & property trends. Regardless of the subject, he will always write blogs of the best calibre. Read more about Tom here.

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About Tom Condon 126 Articles
Tom is a Digital Content Writer passionate about sustainable property & property trends. Regardless of the subject, he will always write blogs of the best calibre. Read more about Tom here.

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