If you are planning to extend your home, one of the biggest decisions is whether to build a single storey or double storey extension.

Both options can create valuable extra space, but they suit different homes, budgets and long-term plans. A single storey extension is often ideal for creating a larger kitchen, dining area or open-plan family space. A double storey extension can add living space downstairs and additional bedrooms or bathrooms upstairs.

The right choice depends on your property, how much space you need, your budget, planning considerations and what you want the extension to achieve.

What is a single storey extension?

A single storey extension adds extra space on one level, usually to the rear or side of the property.

This type of extension is commonly used to create larger kitchens, dining rooms, family rooms, utility spaces, downstairs shower rooms or more open-plan living areas.

For many homeowners, a single storey extension is the most practical way to improve the ground floor layout and make the home feel more spacious, modern and connected to the garden.

What is a double storey extension?

A double storey extension adds space across two floors.

This might mean a larger kitchen or living space downstairs, with an extra bedroom, bathroom, en-suite or home office above.

A double storey extension is often considered when a family needs more space throughout the home, not just on the ground floor. It can be a more involved project, but it can also make a much bigger difference to the overall size and layout of the property.

Which option gives you more usable space?

A double storey extension will usually give you more space overall because you are adding rooms on both levels.

This can be useful if your home feels too small upstairs as well as downstairs. For example, you may want a larger kitchen and dining area, but also need another bedroom or bathroom for a growing family.

A single storey extension may be enough if your main issue is the ground floor layout. If the bedrooms already work well, extending downstairs can still transform how the home feels day to day.

Which is more cost-effective?

A double storey extension will usually cost more overall than a single storey extension because there is more work involved.

However, the cost per square metre can sometimes be better value because the foundations and roof are already part of the project. You are building upwards as well as outwards, which can make better use of the same footprint.

That said, every property is different. Structural work, ground conditions, access, glazing, finishes, bathrooms, kitchens and the complexity of the design can all affect the final cost.

If budget is the main concern, it is important to compare the full scope of work, not just the size of the extension.

Planning permission and design considerations

Planning permission can be a key factor when deciding between a single storey and double storey extension.

Some single storey extensions may fall under permitted development, depending on the size, position and property type. Double storey extensions are often more sensitive from a planning point of view because they can affect neighbouring properties, privacy, light and the overall appearance of the home.

The Planning Portal guide to extensions is a useful place to understand the basics, although it is always best to check the specific position for your own home before moving forward.

Good design is also important. The extension should look like it belongs to the property, rather than feeling like an obvious add-on.

How will the extension affect your home layout?

The best extension is not always the biggest one. It is the one that solves the right problem.

A single storey extension can completely change how the ground floor works. It can help create a brighter kitchen, better dining space, improved access to the garden or a more sociable family area.

A double storey extension can change the whole balance of the home. It may allow you to add a principal bedroom, create a better family bathroom, add an en-suite or make the upstairs layout work better for a growing household.

Before deciding, think about what currently feels wrong with the home. Is the issue downstairs, upstairs or both?

Think about disruption during the build

Any extension will involve some disruption, but the level of disruption depends on the scale and complexity of the project.

A single storey extension may be more straightforward if most of the work is focused around the rear or side of the property.

A double storey extension can involve more structural work and may affect both floors of the home, especially if internal walls, bathrooms, bedrooms or roof details are being changed.

This does not mean a double storey extension should be avoided. It simply means the project needs to be planned carefully, with clear communication and realistic expectations from the start.

Which option adds more value?

Both single storey and double storey extensions can add value when they are designed and built well.

A larger kitchen and family space can make a home much more attractive to buyers, especially when it improves the connection between the house and garden.

Additional bedrooms and bathrooms can also increase appeal, particularly for family homes where upstairs space is limited.

However, value should not be the only consideration. The extension also needs to work for the way you live now. A well-planned project should improve day-to-day life, not just add square footage.

When is a single storey extension the better choice?

A single storey extension may be the best option if:

• You mainly need more ground floor living space
• Your bedrooms and upstairs layout already work well
• You want a larger kitchen, dining area or family room
• You want to improve the connection to the garden
• You have a more limited budget
• You want a simpler extension project

For many homeowners, a single storey extension is enough to make the whole house feel more usable and enjoyable.

When is a double storey extension the better choice?

A double storey extension may be the better choice if:

• You need more space upstairs and downstairs
• You want to add another bedroom
• You need an extra bathroom or en-suite
• Your family has outgrown the whole property
• You want to make the most of the available footprint
• You are planning a more significant long-term home improvement

If you are likely to need extra upstairs space in the future, it may be worth considering whether a double storey extension would be more practical than extending again later.

Speak to Cubit Contracts about your extension

Choosing between a single storey and double storey extension is not always straightforward. The right answer depends on your home, your budget, the available space and what you want the finished project to achieve.

Cubit Contracts works with homeowners across Worcestershire, Warwickshire and the surrounding West Midlands areas, delivering carefully managed house extensions, renovations and design and build projects.

If you are planning an extension and want to understand what may work best for your property, get in touch with Cubit Contracts to discuss your project.