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20 Small House Extension Ideas That Will Make a Big Impact

small house extension ideas for terrace
(Image credit: Fraser Marr)

The best small house extension ideas don't just add new space, they transform existing rooms and layouts. 

Savvy designs for porches, side-return additions and rear extensions can all lighten undue stress put on awkward floorplans while reimagining existing spaces, such as lofts and garages, can add value to any size of home. 

Here's 20 ideas for building an extension that's small, but mighty. 

1. Know What You Want When Looking at Small House Extension Ideas

small extension to terrace house

(Image credit: c/o Create Bespoke)

If you're only looking to add a little, try not to get carried away by sprawling, bank-breaking images for inspiration. Narrowing down where you would like to add a small bit of extra space can make initial searches into designs, styles and ideas far more productive. 

This typical terrace house in London was carefully extended to the side in order to create picture windows for a greater connection to the long garden. 

Also, the same types of bricks were replicated in the new space, tying it in seamlessly with the original house in an utterly contemporary way. 

2. Remember That The Simplest Ideas Can be the Most Effective

small house extension idea for semi-detached house

(Image credit: Darren Chung)

When building an extension to a house, especially one you have inhabited for some time, it can be tempting to want to make huge changes. However, often small strategic extensions can unlock the property's potential more effectively (and for a smaller cost). 

When extending this semi-detached house, a small sympathetic lean-to side addition was added, creating much-needed extra room for storage, a new cloakroom and utility which seamlessly alleviated other high-traffic and cluttered areas. 

(MORE: Extensions for Every Budget)

3. Consider A Small Kitchen Extension for a New Social Space

small kitchen extension to terraced house

(Image credit: Kasia Fiszer)
Looking for more inspiration?

Check out our photo gallery for Small Kitchen Extension Ideas — it's packed with great designs, advice and top tips.

In love with their Victorian terrace but desperate for a change from the dark, dingy and cold kitchen it came with, the homeowners of this extension delicately added a side return extension to provide the extra space they were looking for. 

Rooflights and a stylish kitchen have created a new heart of the home and thanks to the homeowner's DIY efforts, the whole project came in at £45,000. 

4. Get Creative with a Small House Extension Ideas

innovative small kitchen extension

(Image credit: Richard Chivers c/o D-Haus)

Inspired by a curved brick wall in the garden that was used to store bikes, The D-Haus Company knocked through and extended into the small garden space, adding a bright and innovative kitchen space. 

Enlarging the back door opening to make way for a striking pivot door and installing a large skylight above the dining table has further transformed the space. 

5. Try Extending Living Spaces into the Garden

small house extension ideas for terrace

(Image credit: Fraser Marr)

Rethinking the layout of the original kitchen of this terrace has created a more useful kitchen/living area without needing to sacrifice garden space. 

During the building works, the homeowner carefully planned a new garden design and landscaped the outdoor space himself so when the large bifolding doors are stacked back they open onto a tranquil Japanese-inspired space that provides further living opportunities. 

6. Keep an Eye on the Budget with a Small House Extension

small rear extension to house

(Image credit: David Barbour)

Keeping an eye on finances during any sized extension is the key to a successful project, especially with materials shortages inflating expenses at every turn. 

(MORE: How Much Does an Extension Cost?)

7. Let a Small House Extension Enhance Existing Spaces

Rear small house extension ideas

(Image credit: French + Tye c/o MW Architects)

The downfall of many larger extensions is that the shiny new space because the central hub for all goings-on in the house, leaving other areas underused and neglected. 

This creative micro-extension (just 7m2)  achieved everything a bigger extension would – a modern open plan living, kitchen and dining space with views out to the garden– but without the cost of major structural works. 

The money was smartly reallocated by MW Architects for bespoke joinery and high quality, frameless glazing which creates transformative throughviews throughout the ground floor, not just in the new space. 

8. A Basement Might be the Solution to a Small House Extension

Small basement extension idea

(Image credit: French + Tye c/o Paper House Project)
Want to learn more?

Take a look at our guide on How to Create a New Basement

Turning your eye downwards to create new space can be a great idea where plot size is limited or where a loft conversion or rear extension is not possible due to height and size restrictions. 

This rather clever scheme by design practice Paper House Project excavated the ground around an uninhabitable cellar to create a new kitchen. The stepped courtyard and expanded lightwell brings light in, while a small porch extension replaced a dated lean-to. 

9. Add a Small Lean-to Side Return Extension

Side return small house extension

(Image credit: David Barbour)

Building into the slender strip of space alongside terraced or semi-detached houses is tricky to get right but can make a massive improvement. 

While only taking up a small amount of usually wasted space to the rear, a side return extension offers potential to reorganise warren-like layouts. 

A key consideration to make is natural light. This small extension by Archer and Braun Architects utilises a fixed picture window, a large rooflight and contrasting pivot door to connect the kitchen to the outdoors. 

(MORE: How to Transform a Semi-detached Home)

10. Look to the Front for Small Extension Ideas for Semi-detached Houses

Garage small house extension ideas

(Image credit: c/o Shomera Architecture)

This previously converted garage was largely demolished to make way for a new space designed by Shomera Architecture. The extension added around 8m2 to the front of the house, with a newly constructed bay window and zinc roof that ties into the existing house. 

To achieve a similar look, be sure to consider thermal efficiency standards for garage conversions and, if you want to build over a garage, check to make sure the foundations are suitable to carry extra load. 

11. Give the Exterior a Make-over When Adding a Small House Extension

Side small extension ideas

(Image credit: Juliet Murphy c/o The Gentleman Architect)

While respecting the original materials of this terrace house, The Gentleman Architect designed a small side-return extension and dormer loft conversion which truly makes an impact. 

The Corten cladding to both additions elevates the existing house and makes the house feel as one. Large format sliding doors further help to modernise the previously dated property. 

12. Consider a Small Garden Room Extension 

Sunroom small house extension

(Image credit: Vale Garden Rooms)

Whether the purpose is as a new sitting room or home office, creating a garden room or outbuilding is without a doubt a great, and sometimes cost-effective, way to increase space. 

While similar projects as this gorgeous addition by Vale Garden Houses start at £35,000, alternatives can start at £10k — more than a shade cheaper than paying to demolish and rebuild walls!

Glass small house extension to cottage

(Image credit: Jeremy Phillips)

When renovating this cottage, the homeowners chose to simultaneously convert the  derelict granary barn which sat adjacent. By linking with a small glazed extension, their design married old and new effortlessly. 

14. Replace Solid Roofing with Glass to Make Small Spaces Feel Bigger

Small glazed house extension

(Image credit: Simon Maxwell)

By pairing flat rooflights with clerestory windows, what could have been a dark and pokey transition from some space to the next feels light and spacious in this semi-detached extension. 

(MORE: Window Styles)

15. Add a Porch for a Charming Small House Extension

Porch small house extension

(Image credit: Anglian Home Improvements)

Porches are an incredibly practical way to extend a home, without the cost or labour associated with bigger projects. Adding a small addition like this can often be completed under Permitted Development (within limitations) but can add some handy square footage to the floorplan and improves kerb appeal.

This gable end porch by Anglian Home Improvements creates the perfect spot not just to rummage around for keys, but also to house pesky boots and coats. 

16. Think About the Costs of a Small House Extension

Terrace extension built for less than 70k

(Image credit: Malcom Menzies)

Eager to add space but also keep to their budget, the owners of this terrace chose to retain their kitchen's position and add a small dining area adjacent.

Internal windows and existing door frames were also updated so their costs for demolishing the existing structure were reduced.

Also, by opting for a smaller extension, the garden remains a decent size while pergola make great use of the courtyard area. 

17. Going up with a Small Roof Terrace Extension

Small loft house extension

(Image credit: Chris Snook)

For city-dwellers tired of having postage stamp sized gardens – or worse, no outdoor area at all – a roof terrace extension could be just the ticket.  

18. Build a Living Room Extension

Small living room house extension

(Image credit: Darren Chung)

Create a separate sanctuary space with a new extension, like this addition to a medieval cottage. 

Acting as a cosy retreat from the main house, the new room has been sensitively incorporated into the original build with timber cladding

19. Creating a Porch with a Difference

Glass small house extension

(Image credit: Simon Ellis c/o Syte Architects)

This glass box extension was designed as a twist on a conventional porch. Built on a brick platform to create a view of the garden, the structural glass box costs £16,000 from Cantifix.

20. Extending into the Loft 

Dormer small extension ideas

(Image credit: Simon Maxwell)

Going up, rather than out, can be a cost-effective way to adding space, but not all loft spaces are suitable and require a dormer or mansard extension to add some needed head height. 

This unassuming bungalow was transformed into a four-bed family home by Sketch Architects

Amy Reeves

Assistant Editor Amy began working for Homebuilding & Renovating in 2018. She has an interest in sustainable building methods and always has her eye on the latest design ideas. Amy has interviewed countless self builders, renovators and extenders about their experiences for Homebuilding & Renovating magazine. She is currently renovating a mid-century home, together with her partner, on a DIY basis, and has recently fitted her own kitchen.