Single Storey Side Extension: Rules, Cost & Types

Feeling cramped at home or tired of tight corners and limited space? A single storey side extension could be the perfect solution for the homeowners in the UK. It’s one of the easiest ways to add real value and comfort to your home, no matter if you are after a bigger kitchen, a cosy bathroom, or a bright, open-plan living area. 

In this guide, we will walk you through everything, from planning rules, and costs to benefits and how to get started, all made simple and stress free. Paramountbuilt has helped countless homeowners get their desired space without the stress of moving.

Key takeaways

• What a single story side extension involves and why it’s popular.
• When side extension planning permission is or isn’t needed in the UK
• Typical costs, types, permitted development rules,  and comparison.

What Exactly is a Single-Storey Side Extension?

To add space with a growing family, a single-storey side extension is a stylish and smart move. It’s built on one level at the side of your house, perfect for a bigger kitchen, an extra bathroom,  or a new living area. 

Unlike full rear or wraparound extension, this option slides in neatly beside your home’s layout, making it ideal for narrow pots, side alleys, or unused driveways. It’s a great way to unlock the full potential of your property without major disruption.  

Types Of Single-Storey Extension

When planning a single storey side extension, it’s important to know your options. Not all side extensions are the same, each type serves a different purpose depending on your space, budget,and needs.

Let’s explore more about the most popular types so you can choose the one that fits your home perfectly.

Side Return Extension

A side return extension makes use of the narrow alleyway or space that runs along the side of many houses. It’s often used to extend the kitchen or add a downstairs bathroom, creating a brighter, more open layout without major structural changes.  

Side Kitchen Extension

This extension pushes your kitchen or dining space outwards into the side of your property. Perfect for families or those who love to entertain, a single story kitchen extension allows for a larger open-plan layout, more storage, and better flow between cooking and living areas. 

Wrap around extension 

A wrap around extension combines both a rear and side extension to form an L-shape. It’s ideal for maximising internal space, especially in Victorian or Edwardian homes, allowing you to redesign your floor plan completely with wide open areas and loads of natural light. 

Flat pack or Timber Frame Extension

Flat pack or timber frame extensions are prefabricated and brought to your site ready to install. These are great if you want a fast, energy-efficient, and budget-friendly option. They’re also more eco-conscious and can be completed in a shorter time than traditional builds. 

Pro Tip: Creative design ideas for your side extension

Benefits of a Single Storey Side Extension

Homeowners are looking for a smart way to upgrade their home without turning their lives upside-down. A single storey side extension offers just that, more room, better flow, and added value,  all with less hassle.

Let’s explore why so many homeowners are choosing it: 

Fast Build Time with Minimal Disruption

This extension is usually quicker to complete compared to two storey or wraparound builds. Most projects finish within 8-12 weeks, depending on size. Less scaffoldings, fewer structural changes,and a smaller footprint  make the process smoother and less disruptive to daily life. 

More Affordable than Other Extensions

If you are budget-conscious, this could be a smart choice. You’ll save on materials, labour, and design complexity. Since it’s only one level, structural costs are lower, and planning permission is often not required. This keeps both initial and hidden costs under control. 

Increase usable living space 

A single side extension gives you valuable extra space for things like a modern kitchen, an extra bathroom, or a bright dining area. It’s an efficient way to reshape your home’s flow, turning underused side areas into beautiful and functional living zones. 

Boost Property Value

Adding a single-storey side extension can add the market value to your home by 10-20%, depending on the design and location. It makes your property more attractive to the buyers by adding practical living space.

Great for Narrow or Urban Plots 

Side extensions are perfect for homes with limited rear space, especially in city areas. If you’ve got a narrow plot or an unused alleyway, a side return can be used creatively, which helps turn waste into a sleek kitchen or utility areas without major structural changes. 

Easier Planning Approvals or Permits

Since many single-story extensions fall under permitted development rights, you might not need full planning permission. This speeds up the process, lowers legal costs, and helps you get started faster, especially useful for smaller, straightforward builds in typical residential zones. 

Custom Design Flexibility

You have full freedom to personalise your extension’s design, no matter if its skylight, bifold doors, or seamless flow into the garden. This flexibility makes it easy to customise the space for your lifestyle, from a calm reading nook to a vibrant kitchen-dining hub. 

Permitted Development Rights for Single Story Side Extension

For those who want to avoid the stress of full planning permission, permitted development rights might let you build your single-storey side extension without applying for permission if your design follows the rules. It’s faster, easier, and can save time and money. But the key is knowing exactly what’s allowed. Let’s break it: 

What are Permitted Development Rights?

Permitted development rights are planning rules that allow certain types of building work , like small extensions, to go ahead without formal approval. For a single storey side extension, this means you may not need to submit a planning application, as long as you meet all PD conditions. 

Key rules for side extension under PD: 

• Your extension must be single storey only
• It can’t be wider than half of the original house. 
• The height must not exceed 4 meters
• It must not extend beyond the front of the house or face a highway. 
• Materials should be similar to the existing property. 

Building Regulations for Single story side Extension

Even if your side extension doesn’t need planning permission, you still need to follow UK building regulations. These rules ensure your new space is safe, energy-efficient, and structurally sound.

Let’s break down the key areas you’ll need to think about before starting the build:

• Structural safety and foundations 
• Insulation and energy efficiency 
• Fire safety 
• Ventilation 
• Drainage 

Do You Need Planning Permission for Single Storey Side Extension?

Those wondering, “Do I need planning permission for a side extension?” Here is some good news for them. In many cases, you don’t need planning permission for a single-storey extension if your project meets certain conditions under Permitted Development Rights. 

For instance, if your side extension is only one storey, doesn’t exceed 4 meters in height, and is no wider than half of the original house, you may not need approval. This applies to most standard homes, but planning permission for a side extension is still required if your property is listed, in a conservation area, or if you are making a side return extension that wraps around the rear.

When in doubt, always check with your local planning authority. It’s the best way to avoid delays or costly mistakes when navigating side extension planning permission in the UK.  

Cost of a Single Storey Side Extension 

The single-storey extension cost in the UK usually ranges from £1800 to £3500 per square meter. For a modest side build, you can expect to pay between £20000 and £35000, depending on size and finishes. High-end or complex extensions may push the single-storey extension cost beyond £50000. Don’t forget to include extras like VAT, architects’ fees, planning costs, and a 10-5% contingency for unexpected issues.  

Comparison of single-storey extension over other extensions 

How Do You Find the Right Architect for this Extension?

• Ask for examples of single storey side extension projects they’ve done 
• Look for members of RIBA or chartered practices experienced in PD rules 
• Get clear estimates, check references, and discuss timelines upfront