10 extension ideas for semi-detached houses – single and double storey transformations

Want to build outwards while being mindful of a neighbouring property. Our extension ideas for semi-detached houses will help

Thinking of expanding your living space? Consider these extension ideas for semi-detached houses to see how best to convert your home, to add both space and value to the property. With a semi-detached property it's especially important to be mindful of the neighbours, because their house is attached to yours.

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'For many of our clients, one of their biggest concerns as they look to undergo an extension on their homes, is the impact this process is going to have on their neighbours,' says Ana Delgado at Structural Repairs .'Home extensions are known to be quite invasive, not only with on-site disruptions, unsightly excavation processes, noisy commotions and lengthy timelines, but also in regard to the end results.'

'However, there are certain preventative actions which can be advised as a means to minimise home extension disruptions. Making them as neighbour friendly as possible!'

First and foremost ensure the work you are conducting is classed as part of your 'permitted development rights'. Or if not, make sure you apply and have your plans approved to legally comply with regulations.

Our guide to building an extension on a house – will explain the basics of what to do, where to start and planning permission. Or read on for inspiration as you start the extension process.

Extension ideas for semi-detached houses

1. Dig deep for a basement extension

the back of basement extension in a large period home

(Image credit: Future Publishing Plc/ Rachael Smith)

Add an extra floor, without altering the exterior by going into the basement. But be mindful of the works involved.

'Basement kitchen convesions and excavations take a lot longer than regular extensions, as the excavation process is a slow and steady phase of the build' warns Rob Wood at Simply Extend. 'A basement conversion build process takes around five months, unlike a typical house extension which takes between 8-12 weeks.'

It will also most likely requires planning permission, although Rob does add, 'Occasionally, if your basement does not have a lighting well and is a small project, it may fit within permitted development restrictions and not need planning permission.' But it's imperative to check before you set your heart on carrying out the work. Check the

2. Extend up and out

extended semi detached house

(Image credit: Tom Meadows)

Many semi-detached properties will still offer the opportunity to extend to the back. But you may be lucky enough to have land to the side of the property that you can build into, as seen here.

If that's the case, and the extension will be viewed from the front of the property, it's important to match the brickwork and other features, such as windows and roof tiles. Local planners will be far stricter with alterations that can been seen from the front, and more likely to want them to be in keeping with what's already there.

If that doesn't give you enough space, look to the loft to add a subtle dormer extension to the back – our attic bedroom ideas show what's possible.

3. Steal space from the garden

reclaimed brick extension

(Image credit: David Still)

This neat one-storey extension is one of the most affordable ways to extend. Plus, it offers more privacy than a longer stretch of bi-folds running the full length of the property. If you can afford to steal that little bit of space from the garden, it's a surprisingly cost-effective way to get more room.

We also love how spotlights have been incorporated under the window, for extra outdoor wall lighting.

4. Create a viewing room

house with lawn

(Image credit: Cece Wilden)

Open up the back of the property with a thoughtful extension which uses large glass windows to create a viewing room. This extension creates vast amounts of extra space for the main living room but additionally it welcomes volumes of light thanks to the glass panel walls within the corrugated steel-box extension.

When you are extending to the rear of a property, it's often possible to create an extension that contrasts with your existing home. In fact planners seem increasingly approving of this approach – though always check in your area. The juxtaposition of styles tells its own story of the history of your home.

5. Extend the aesthetic

brick house with garden and white armchair

(Image credit: Tom Meadows)

Create a harmonious exterior with an extension built from reclaimed bricks that match the original property. It may be more expensive, but keeping the aesthetic consistant will help the new space blend seamlessly into the rest of the house – and keep the local planning office happy!

Though the steel-framed bifold doors contrast with the sash windows above, they still blend with the roof tiles and guttering, so don't feel out of place.

Related: Crittall windows – everything you need to know about steel frames

6. Think about access

kitchen extension

(Image credit: Future PLC/Alistair Nicholls)

One thing to consider when extending a semi-detached or terraced house is access. Building out to the side may involve losing a side door. But it's not practical to have to open up bi-folds whenever you want to access your garden.

That's why we love this clever sliding doors design. A large stretch of glass runs across and around the corner of the building. Not only does this create a seamless link between inside and out, it also allows the owners to just open the side glass door if they need to slip out quickly. It's the perfect blend of practical and stylish.

7. Run a light well along the side return

rear kitchen extension

(Image credit: Future PLC/Chris Snook)

This extension takes two directions to really get the most light possible into this home. the side return has been filled with a light well, with a floor-to-ceiling window and glass roof. But by not bringing it in line with the back extension, the owners have been careful to ensure that plenty of natural light is still being pulled into the centre of the house.

Colour-matched stone has been used indoors and for the patio area for a seamless blending of the spaces. See our patio ideas for more ways to work your garden paving.

8. Stretch across into the garden

house with exterior table and chairs

(Image credit: Future PLC/Darren Chung)

A sympathetic extension doesn't have to simply mean one that matches your existing property. It can be used to describe ways to unite old with new in a harmonious way. This modern extension sits on the back of this period semi-detached brick house at ease thanks to its earthy panelled exterior and picturesque living roof.

The side of the extension features retractable glass doors to allow a natural transition from indoor to outdoor. And consider your neighbours – this living roof provides something pleasant to look at from their perspective, as well as yours.

9. Pop on a porch

house with white wall

(Image credit: Future PLC/Lizzie Orme)

If your front door is located at the side of your semi-detached property it may run straight into a main living area, most likely a living room.

Adding a porch extension makeS the entrance a separate space. This will give you more options when it comes to positioning furniture in the adjacent room and make it feel like less of a corridor or dumping ground.

10. Extend into the side return

kitchen with white wall and wooden worktop

(Image credit: Velux)

Often the first and most obvious option in a Victorian semi, use a side return to enlarge the kitchen space and create an open-plan living area or add a utility room of dreams.

Of course, this may mean it's tricky to add windows to the side of the house if you are close to neighbouring houses, so bring in the light with roof windows like these from Velux.

Where should you start when planning to extend a semi-detached house?

Before you start planning an extension, of any kind,  it's important to really think and visualise what you want from the new space you are creating – and how you'll use it.

Design expert Rob Wood at Simply Extend says to consider 'Do you need a larger kitchen? Do you want an extra living area? This will help guide the type of extension you need, and how you will design the new floorplan.'

How much can you extend a semi-detached house?

'If you do not live in a conservation area, and you live in a house not a flat, you can extend from the rear of the property by 4m into your garden space,' advises Rob.

Is it worth extending a semi-detached house?

A home extension on any type of property is always a worthwhile investment because it can increase its value significantly. This, of course, applies to semi-detached houses.

'There are also more options for most semi-detached houses,' explains Rob. Pointing out that with a semi-detached house you have the benefit of 'being able to have side return and wrap-around extensions.'

Next up: Glass extension ideas – create light-filled glazed spaces to enlarge and enhance any home

Can I build a two storey extension on semi-detached house?

'In some occasions you can, but planning permission will be required from your local council' advises Rob. 'If the design is too imposing, the planning department may push back and refuse permission or you may need to alter your plans.'

Talk your plans through with an architect who will be able to advise on the most common design problems associated with semi-detached extensions.


Tamara was Ideal Home's Digital Editor before joining the Woman & Home team in 2022. She has spent the last 15 years working with the style teams at Country Homes & Interiors and Ideal Home, both now at Future PLC. It’s with these award wining interiors teams that she's honed her skills and passion for shopping, styling and writing. Tamara is always ahead of the curve when it comes to interiors trends – and is great at seeking out designer dupes on the high street.