Building an extension is an exciting way to make your home work better without the upheaval of moving. Whether you need a larger kitchen, more room for family life or a flexible space that can adapt over time, a well-designed extension can make a noticeable difference to both your home and your day-to-day routine.
But before you start thinking about roof colours, bi-fold doors or kitchen units, there are some bigger decisions to make. The size and position of the extension, how it connects to your existing rooms, the roof design, natural light, insulation and foundation all need to work together.
Our range of single-storey home extensions can be tailored around different properties and requirements, with pitched, flat and lantern roof options available alongside a wide choice of glazing, cladding and finishes.
So, what should you consider before building?
It sounds obvious, but the best place to start is not with the extension itself. Start with how you want to use it.
Think about what is missing from your current home.
Perhaps the kitchen is too small for the whole family. Maybe you want somewhere to eat that opens onto the garden, a quieter home office or simply a larger room where everyone can spend time together.
A single-storey extension can be used to create:
Having a clear purpose for the new space makes the rest of the design process much easier.
It also helps you avoid building an extension simply because you have the available space. The aim should be to create additional space that genuinely improves how your home works.
One of the most important parts of any extension is the point where the new space meets the original house.
An extension can look impressive on paper but still feel awkward if the transition between the two areas has not been considered carefully.
Think about how you will move between rooms, where furniture will go and how the new space will be used throughout the day.
For example, if you’re extending a kitchen, you may want a clear route between the cooking area, dining space and garden. If an existing wall is being removed, consider whether the resulting open space will still have distinct areas for cooking, eating and relaxing.
You don’t necessarily need to create one enormous open-plan room either.
A broken-plan layout can provide a useful middle ground, allowing different areas of the extension to feel connected while still having their own purpose.
The roof is one of the biggest design decisions you’ll make.
It affects the external appearance of the extension, the internal ceiling height and the amount of natural light you can introduce. It can also determine how well the new structure sits alongside the existing property.
There are several options to consider.
A pitched roof can be particularly effective when extending a traditional or period property.
Different profiles can be used to complement the architecture of the original building, including Edwardian, Edwardian hipped, lean-to, lean-to side hipped and gable-end designs.
Pitched roofs can also provide opportunities for roof windows and other glazing features, helping to bring daylight further into the extension.
If you’re interested in the costs and specification of this type of build, you can also explore our guide to pitched roof extension costs.
Flat roofs offer a cleaner, more contemporary appearance and are particularly well suited to modern kitchen extensions and open-plan living spaces.
Their low-profile design can help keep the extension visually unobtrusive, which can be useful where you want to add space without making the new structure feel too dominant from the garden.
A flat roof also provides flexibility when it comes to glazing. Roof windows and fixed roof glazing can be incorporated to bring more daylight into the room, while the simple roofline works well with large areas of architectural glazing.
For homeowners looking for a modern extension with clean lines and plenty of design flexibility, a flat roof can be a practical option.
If bringing more natural light into the extension is one of your main priorities, a lantern roof is another option worth considering.
A roof lantern sits above the main roof structure, allowing daylight to enter from above and creating a more open, spacious feel inside the room.
This can work particularly well over larger kitchen and dining areas where the centre of the room might otherwise be further away from the external windows.
A lantern can also become a feature in its own right, giving the extension a stronger architectural identity while helping to make the new space feel bright and inviting.
Natural light should be considered alongside the roof design rather than as a separate decision.
The position of windows, doors and roof glazing can all influence how bright the finished extension feels.
Large rear windows and bi-fold doors can create a strong connection with the garden, but they may not be enough to illuminate a deeper extension evenly. Roof windows, fixed roof glazing or a lantern can introduce light from above and help spread daylight further into the room.
Think about how the light will change throughout the day as well.
The direction your extension faces, the position of neighbouring properties and surrounding trees can all affect how much sunlight reaches the room. Good design is therefore about more than simply adding as much glass as possible.
The aim is to create a comfortable space with a good balance of natural light, views, privacy and solar control.
Your choice of windows and doors can have a major impact on both the appearance and functionality of your extension.
For a garden-facing room, you might consider:
There is no need to choose the largest possible opening simply because the space allows for it.
Consider how you will arrange your furniture, where the sun will fall and how you want to use the garden. A well-positioned smaller opening can sometimes work better than a huge expanse of glass that leaves little wall space for furniture.
An extension should feel like a natural part of your home throughout the year.
This means thermal performance needs to be considered during the design stage, rather than treated as an afterthought.
The walls, roof and floor all contribute to the overall performance of the extension. A properly designed structure with high-quality insulation can help reduce heat loss and create a more comfortable internal environment.
Modern extension systems can incorporate insulation directly into the wall and roof structures, helping to achieve the thermal performance required for a permanent living space.
It’s also worth considering ventilation when planning an extension. A well-insulated room still needs adequate ventilation to maintain good indoor air quality and manage moisture.
The foundation is another important part of the project, even though most of it will eventually be hidden beneath the finished extension.
Depending on the property and site, you may be able to use an existing suitable base, while other projects will require a new foundation.
Ground conditions, the size and design of the extension and the requirements of the existing property all need to be considered before deciding on the most appropriate approach.
For suitable projects, a modular foundation system such as Durabase can provide an alternative to a conventional foundation approach. The system combines a durable steel base with modular construction, providing a solid platform for the extension while helping to streamline installation.
The right foundation solution will always depend on the individual project, so it should be assessed as part of the wider design rather than selected in isolation.
Planning requirements are something you should establish before committing to your extension design.
Many single-storey extensions can be built under Permitted Development Rights, provided they meet the relevant conditions and limitations. However, not every property or proposed extension will qualify.
The size and height of the extension, its position on the property and the type of house you live in can all affect whether planning permission is required.
Additional restrictions can also apply to properties in conservation areas, National Parks, Areas of Outstanding Natural Beauty and other designated locations. Listed buildings may have further requirements.
Even when planning permission isn’t required, the extension will generally still need to comply with Building Regulations. These cover areas such as structural safety, insulation, fire safety, ventilation and drainage.
If you’re uncertain about what applies to your property, getting professional advice early can help prevent costly changes later.
The cost of a home extension can vary considerably depending on the size, specification and complexity of the project.
The roof is one factor, but it is far from the only one. Foundations, glazing, insulation, doors, cladding, internal finishes and site requirements can all affect the overall cost.
It is therefore useful to establish your priorities before finalising the design.
For example, if creating a bright kitchen-diner is your main objective, you may decide that large areas of glazing and roof windows are worth prioritising. If the external appearance is particularly important, you may want to allocate more of your budget towards the roof and cladding.
Having a clear specification also makes it easier to compare different options and understand what you’re getting for your budget.
Your extension should work with the existing property, but that doesn’t necessarily mean it has to look identical.
A contemporary extension can sit comfortably alongside a traditional house when the proportions, colours and materials have been chosen carefully.
Cladding, roofing, windows, fascias and gutters can all be used to create a visual connection between the original house and the new addition.
For example, you might choose a contrasting modern cladding colour while matching the roof or window finish to existing features.
Our extension systems can be supplied with a choice of external finishes, including low-maintenance PVC-UE cladding. Extensions can also be supplied without cladding where a homeowner wants to apply their own rendered or timber finish.
The extension shouldn’t be designed in isolation from the garden.
For many homeowners, creating a better connection between the house and outdoor space is one of the main reasons for extending in the first place.
Consider where your main doors will open and how the area immediately outside the extension will be used.
Will there be a patio or seating area? Do you want a clear route from the kitchen to the garden? Will large doors leave enough wall space for kitchen units or furniture?
These decisions can have a surprisingly large impact on how practical the finished extension feels.
The roof design can also influence the relationship with the garden. A low-profile flat roof may help maintain an open feeling, while a pitched or lantern roof can give the extension more architectural character.
It’s easy to design an extension around your current requirements, but it’s worth considering how those requirements might change over time.
A growing family may need more flexible living space. A home office might become a guest room. Children may eventually need less play space but more privacy.
Where possible, create a layout that can adapt.
An open-plan kitchen and dining area, for example, can be designed with different zones rather than one completely undivided room. This gives you more flexibility when furniture and household needs change.
Good extension design isn’t necessarily about predicting exactly what your home will look like in ten years. It’s about giving yourself enough flexibility to adapt.
It’s also worth thinking about how the extension will actually be built.
Traditional building projects can involve coordinating numerous materials, trades and construction stages on site. Depending on the project, this can make the process longer and more difficult to manage.
A modern modular extension system can simplify parts of the process by using precision-engineered structural components that are manufactured before installation.
This doesn’t mean every extension is identical. There is still considerable scope to customise the finished structure, from the roof profile and glazing through to cladding, doors, roof windows and finishing details.
For homeowners, this can provide a useful balance between a structured construction system and the flexibility needed to create an extension that suits an individual property.
It is easy to focus on how an extension will look from the garden, particularly when choosing roof materials, cladding and glazing.
But the most important view is arguably the one you’ll experience every day from inside your home.
Think about what you will see when you walk into the extension. Where will your eye naturally be drawn? Will the kitchen have a clear view towards the garden? Will roof glazing brighten the centre of the room? Does the ceiling height feel right for the size of the space?
These details can make a significant difference to how comfortable and spacious an extension feels.
A successful design should therefore work from both directions. It needs to complement the existing house externally while creating an interior that feels like a natural continuation of your home.
There is no single design that will suit every property.
A Victorian terrace may benefit from a carefully proportioned pitched roof, while a modern house could lend itself to a clean-lined flat roof. A larger kitchen extension might benefit from a lantern or additional roof glazing where natural light is a priority.
The important thing is to consider the project as a whole.
Layout, roof design, glazing, insulation, foundation, external finishes and planning requirements all need to work together. Getting those decisions right at the beginning can make the finished extension feel far more natural and useful.
If you’re considering adding more space to your property, our home extensions are designed to give homeowners flexibility over the structure, roof style, glazing and external finish.
Choose from pitched, flat and lantern roof options, with additional features including roof windows, fixed glazing, bi-fold and patio doors, different cladding finishes and a choice of roofing materials.
Whether you’re planning a larger kitchen, a bright family room or a more flexible ground-floor layout, our design team can help you explore the options available for your home.
We offer free designs, fast no-obligation quotes and expert advice, with solutions available to homeowners and independent builders across England and Wales.
Ready to start planning your extension? Get in touch with our team on 01202 399999 to discuss your project.
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