Your family is growing… but the walls aren’t.
It’s a problem every UK homeowner runs into at some point. The children are crammed into bedrooms together and the kitchen is so small you can hardly move!
So what’s the answer?
You extend.
But here’s where it gets tricky:
Do you build out to the side… or up to the sky?
You gain space with either option. They each cost a small fortune. And both will change your family’s life forever.
This guide breaks down exactly which one suits a growing family best.
Here’s what’s covered:
- Why Families Are Choosing To Extend
- Side Additions Explained
- Upward Builds Explained
- Which One Suits A Growing Family?
- Cost Comparison Between The Two
- Planning, Disruption & Timing
Why Families Are Choosing To Extend
The numbers tell the story.
ONS stats say there were 19.9 million families in the UK last year — and many of them are shoehorned into houses built with no concept of how families live now. Open-plan kitchens, homeworking space, playrooms… these were not part of the remit when most UK housing was constructed.
Typically, the decision begins around the kitchen. A fitted kitchen extension cost is one of the largest expenses when renovating your home. It can determine if you extend outwards for a larger ground floor space or if expanding your home upwards is a better option. Extending sideways will eat into your garden for a larger kitchen-diner. Building up will allow you to keep your garden and gain bedrooms and bathrooms.
Each is correct. Both have massive advantages. It really just depends on what your family is lacking more of — and how much money you want to spend.
Pretty important decision, right?
Side Additions Explained
A side extension (also known as a single-storey extension) is pretty much what it says on the tin. An extension that builds out from your existing footprint, typically out into the back garden or down a side return.
Here’s why families love them:
- More open-plan living space
- Bigger fitted kitchen with a dining area
- A space for kids to play within sight
- Better connection to the garden through bi-folds
Expect to pay between £2,200 and £3,300/m² for the fitted kitchen extension cost for a single-storey build. Plus the kitchen units, worktops and appliances themselves will cost another £5,000 to £15,000.
But there’s a downside:
You lose yard. Lots of yard. When you have young children and spend time outside every weekend…ouch.
Side additions only provide you with one kind of room. You usually end up with downstairs living space and that’s it. If you need bedrooms, tough luck.
Upward Builds Explained
An upward build takes your current single-storey extension and builds another storey on top of it… or creates a two-storey extension completely.
It’s the smarter long-game move for many families. Why?
Because you keep the garden.
The Federation of Master Builders state that two storey extensions are £1,000 – £2,500 per m². This equates to lower per square meter cost than a single storey extension when you account for the foundations and roof being split across two levels.
What you get with an upward build:
- Extra bedrooms upstairs
- A second bathroom or en-suite
- A home office or playroom
- A bigger kitchen-diner downstairs
- The garden stays intact
That last point right there is massive. Garden space equals mental health space for growing families. Sacrificing it for a bigger kitchen will rebound against you in year 3 when you want a trampoline for the kids but have no room.
Which One Suits A Growing Family?
Here’s the honest answer:
It depends what you need more of.
If the problem is “we need a bigger downstairs” — side addition wins.
If the problem is “we need more bedrooms” — upward build wins.
If your issue is “we want both” — then a wrap-around or a two-storey extension is the solution.
For the majority of growing families, the deciding factor always comes down to bedrooms. You can fit 4 people in a small downstairs apartment and survive. You can’t fit 4 people into 2 bedrooms long term.
That is why so many homeowners opt for the upwards build, even when the fitted kitchen extension price matches up with a side build. The investment returns more in the long run.
Speaking of return…
National statistics indicate that increasing floor area with an extension will increase your property value by as much as 25%. That’s significant equity — and bedrooms count for more in an appraisal than a designer kitchen alone.
Cost Comparison Between The Two
Money matters. Let’s break it down:
Side Addition (single-storey):
- £2,200 to £3,300 per m²
- 20m² build: roughly £44,000 to £66,000
- Add £5,000 to £15,000 for the fitted kitchen itself
- Less disruption, quicker build time
Upward Build (double-storey):
- £1,000 to £2,500 per m²
- 40m² build over two floors: around £40,000 to £100,000
- Better cost per square metre
- More disruption but more space gained
Fitted kitchen extension cost appears on both because most households opt to remodel the kitchen too at some point. Price really differs by what else you get.
By extending outwards you gain one large room downstairs. By extending upwards you gain a larger kitchen-diner AND additional bedrooms upstairs.
Same money. Different outcomes.
Planning, Disruption & Timing
Quick reality check before jumping in:
- Side additions often fall under permitted development if under 4m deep
- Upward builds almost always need full planning permission
- Side additions take around 12-16 weeks
- Upward builds take 14-20+ weeks
- Expect to have to relocate (or reside amongst the dust) during an upward construction
Planning is where many families run into trouble. Don’t expect the project to be smooth sailing — inquire at your local council early on, and expect to pay architects fees in addition to construction costs.
Final Thoughts
There’s no universal “right answer” here.
A side extension is ideal if your family requires additional ground floor living, you have enough garden space to sacrifice and the project needs to be completed quickly.
An upward build would be preferable if bedrooms are your sticking point, protecting the garden is key, and build time isn’t an issue.
To quickly recap:
- Side additions = more downstairs space, lose garden
- Upward builds = more bedrooms, keep garden
- Cost per square metre is better with upward builds
- Fitted kitchen extension cost is similar across both
- Both can boost property value — bedrooms tend to add more
Whether you DIY or employ a builder. Plan it. Get drawings. Get 3 quotes. And budget an extra 10-15% on top for contingency.
A growing family is worth getting this right.
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