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Single Storey Extensions

They’re versatile, come in a range of shapes and sizes, can be tailored to varying budgets, and they can help transform the layout of your home. Yes, we’re talking about the ever so popular single storey extensions. And, if you’ve landed here, perhaps you’re curious about the ins and outs of this extension for your own home.

Like with any major home improvement project, there’s many things to consider before you make the leap to the construction site. How much do single storey extensions cost? Do you need planning permission? Which type of extension is going to be right for your home?

If the details have got you scratching your head, have no fear. At DiA, we’re here to help homeowners take on extension projects big and small. Here are the basic facts you need to know to get your journey started.


There are reasons single storey extensions are one of the most popular projects out there. If you’re still thinking about starting your own project, consider these important plus points early on.

1. Cost-effective alternative to moving house

One of the main reasons why people choose to make a big change to their living arrangements is space. Whether because your family is growing or because your current situation is getting a bit untenable, the hunt for space can lead you in two different directions – moving or extending.

Moving can be a tempting option but isn’t always the easiest one and definitely not the cheapest. Alongside the price of your new property, you’ll also need to budget for…

  • Stamp duty
  • Valuations and surveys
  • Legal fees
  • Insurance
  • Estate agent fees
  • Deposit, mortgage costs and broker fees

And there’s no guarantee that you’ll find a home perfectly suited to your new requirements. In comparison, extending your property allows you to stay in the area you love, create tailored space for your needs, and potentially make a profit, should your extension boost the price of your home.

2. Brings value to your property

As we touched on above, one of the biggest benefits of extending to the potential of increasing the value of your property. While ceiling prices can hamper these goals in certain areas (we recommend talking to an estate agent on this), for areas where space is at a premium you can get a real return on your investment, which in turn can be utilised to help fund your single storey extension should you capitalise on your home’s equity for funding.


Single storey extensions are highly versatile and there are plenty of design options available to suit a variety of property types and budgets. Here are some of the most popular that you might consider for your project.

1. Single storey wraparound extension

A wraparound extension brings together both a rear and side extension into one continuous space. They require more structural work than side and rear extensions, and very rarely come under permitted development rights. However, because you’re using space from two directions, wraparound extensions can be a great way of getting lots of extra room without your garden getting gobbled up in the process.

2. Single storey wraparound extension

Just because you live in a bungalow doesn’t mean you can’t extend your home. There are plenty of single storey extension options out there for this property type, allowing you to get more space and to modernise. Because bungalows tend to be a little older than other
properties, there will be some points to bear in mind in terms of construction, as well as some unique planning hurdles.

3. Single storey side extension

If you’re lucky enough to have an alleyway that’s going spare, then it’s time to breathe some new life into this dead space with a single storey side extension. This small and mighty single storey extension can help expand your kitchen, help you squeeze a new utility room, or even be used for a downstairs WC – the options are endless! What’s more, they don’t always require a full planning application.

4. Single storey rear extension

A rear extension is a classic for a reason. By taking your home out towards the rear, you can add heaps of space and really transform the layout of your ground floor. What’s more, you can add twice the amount of space with a rear extension than you can with other single storey extensions, if you choose to use your permitted development rights – up to 8 metres, in fact!


The cost of a single storey extension will vary hugely depending on these deciding factors:

  • Size
  • Complexity
  • Materials
  • Quality of chosen contractor
  • Location in the UK
  • Condition of soil and existing building

Because of this, a single storey extension in the UK could cost anywhere between £30,000 – £250,000.


Alongside what type of single storey extension you want to pursue, you’ll also need to decide on which roofing best suits the project. Luckily, there are only two options you need to decide between.

1. Pitched roof single storey extension

Pitch refers to the angle your roof sits at, so a pitched roof single storey extension has a roof which is tilted to some degree. They are typically used to give a more classical look to your extension, and to help it blend in better to period properties. They also tend to
provide a better quality of build, as they aren’t as prone to collecting rainwater and the extra height allows for more insulation.

2. Flat roof single storey extension

As the design for flat roof single storey extensions has improved, and helped to eliminate many of their downsides, more and more people are opting for this style of roof. It can help provide a modern look to your facade and can be quite cost-effective. These
benefits might be just enough to help you overlook the extra maintenance work that’s potentially involved with their upkeep.


Yes, there’s quite the shopping list when it comes to single storey extensions. Another major consideration will be your glazing. How much glass you choose to incorporate in your window and doors will affect your connection to your garden, how much natural light you enjoy, but also the price tag of your project. Here are some options to think about.

1. Bi-fold doors

Bi-fold doors have exploded with popularity in the last few years and it’s not hard to see why. The door is made up of panes of glass, which on their hinges can concertina open. This allows you to enjoy a fully open wall, which can be a challenge for sliding doors to achieve if there isn’t space in the wall cavity for the glass to go. You only need a minimum of three sections, so they can be fitted to entrances both big and small and can even be used in conjunction with a floating corner.

2. Sliding doors

Sliding doors have been a well-used option for many decades and continue to be very popular. They can be fully glazed, creating large swathes of glass for you to enjoy at the rear of your home. They can also be very space efficient too. While bi-fold doors take up room to the side once folded, sliding doors can slip into the wall cavity, creating what is known as a ‘pocket door’.

3. French doors

For those who like a classic touch, there’s nothing better than French doors. While not as expansive as the options listed here, many homeowners choose to add several sets of doors to large walls to create a similar effect and let in large amounts of natural light into your home. If you’re looking to add some retro character into your single storey extension, French doors are an excellent choice

4. Feature windows

Alongside your doorway, you might want to create a feature window, for that extra bit of luxury. Our Happy Home research showed that having stunning views of nature does more for a homeowner’s wellbeing, than just having natural light in your space. Therefore, it’s a
good investment to make! You could opt for floor to ceiling windows, bay windows, or even oriel window boxes.


Do you need planning permission for a single storey extension? Not necessarily!
According to the law, homeowners can add extensions to their homes without applying for planning permission when they use their permitted development rights, as long as the extension follows the stipulated requirements.

Regardless of these restrictions, many homeowners prefer to build within their permitted development rights as it’s a safer route. Permitted development is not subjective, saving homeowners the stress and added expense of re-doing an application in a situation where the first application is not approved. The fact that you can build an impressive extension within its
regulations is, of course, a bonus.

It’s worthy of mention that permitted development rights aren’t applicable in all situations.

Flats, Maisonettes and Listed buildings – These properties are not covered by permitted development. In the same vein, owners of houses located in conservation areas or areas of outstanding beauty have limited permitted development rights.

1. Lawful development certificates

Building within your permitted development rights eliminates the need for full planning permission. Nevertheless, it’ll be good if you apply for a lawful development certificate.With this document, you’ll be able to prove that your project was compliant when it was
built. This document will particularly come in handy if you ever sell your home.

The criteria for building within permitted development rights for different extensions are stated below. However, it’s recommended that you seek professional guidance to ensure you’re building within your permitted development rights.

2. For single storey extensions

For a single storey extension to be permissible under permitted development rights:

The size of the extension must not exceed half of the land area around the initial house. This covers the time since the property was built. As a result, you must factor in if any previous owners have carried out extension works in the land before

The extension, after it’s built, must not be nearer to the public highway.

No part of the extension can exceed the highest part of the roof of the original house.

Its eaves and ridge height must not be higher than that of the existing house.

Materials used for the extension must be similar in appearance to the current house.

It cannot include a veranda, balcony, microwave antenna, chimney, flue, soil, and vent pipe.

No alterations can be made to the roof of the existing house as well.

3. Wraparound extensions

Permitted development rights do not cover wraparound extensions. Wraparound extensions are a combination of side and rear extension, meaning your project will be assessed as a side extension and a rear extension respectively. The space a wraparound
extension requires plus its structural complexity makes it an unlikely candidate for permitted development rights.

4. For side extensions
  • For a side extension to be permissible under permitted development rights:
    • The side extension must be single storey
    • It must have a maximum height of 4m
    • It must not exceed half of the widths of the original house
    • It must not front into the road
5. For rear extensions

Rear extensions are very common and are a great way to use the extra space at the back of the house. For a rear extension to be permissible:
Single storey rear extensions must not be longer than the rear wall of the original house by more than 3m (for a semi-detached house) and 4m (for a detached house)
Its maximum height must be 4m.
Single storey rear extensions can use ‘prior approval’ to double this allowance, allowing you to extend up to either 8m (detached) or 6m (other).

6. How big can I build a single storey extension without planning permission?

Permitted development rights allow homeowners to install an extension of up to 6m for a semi-detached or terraced house and 8m for a detached house, but only by going through the prior approval process. If you want to avoid prior approval, your allowance will be up to 3m or 4m, depending on your property type.

Before planning your extension, you should find out if previous owners have added an extension to it in the past. This is because extensions carried out by previous owners will eat into your permitted development rights, limiting how big you can build your extension
without planning permission.

7. Other restrictions you need to check before building a single storey extension?

Here’s a breakdown of some other restrictions you should check before building a single
storey extension.
You should ensure your project is building regulations compliant. Building regulations are laws that guide how a house should be built before it’s considered habitable. These laws are geared at the safety of the building, environment, and the inhabitants and cover things like ventilation, insulation, structure, and fire safety.
Another restriction you might run into is party wall agreement. They’re designed to protect the interest of your neighbours when doing structural work on a shared wall. You’ll need to serve them a party wall notice and obtain written consent for the works within 14 days.
However, if they do not grant you written permission, you’d need to contact a surveyor to arrange party wall agreements.
Similar to the party wall agreement is prior approval. They’re similar in that they both protect your neighbour’s interest but differ in that you do not need to share a wall with the supposed neighbour before they raise their concerns. Prior approval comes into play when you’re adding a larger rear extension, between 3-6m or 4-8m (if your home is detached). It allows your neighbours to voice their concerns if your new extension leads to a loss of privacy, natural light or constriction of views.



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