5 Ways to Choose the Right Size Home Extension For Your Needs!

Written by Ollie Cornish on October 27, 2025. Posted in News.

5 Ways to Choose the Right Size Home Extension For Your Needs!

This comprehensive guide reveals everything homeowners in Solihull and Warwick need to know about getting the size of their extension right in 2025.

Based on our experience building extensions across the area and honest conversations with families about what worked and what didn’t, we examine the five things that determine whether your extension will be brilliant or disappointing, and how to avoid spending good money on something that doesn’t quite solve your problem.

Key topics covered:

The five things you need to think about when deciding how big to go
How different sized extensions affect what your house is worth
What extensions actually cost per square metre around here
Planning rules and how big you can go without permission
Room sizes that actually work for real family life
The expensive mistakes people make with extension sizing
Getting the balance right between cost and usefulness
What works for different types of houses across our area

Getting the Size Right: It’s About More Than Just Metres

Choosing how big your extension should be is one of the most important decisions you’ll make. Too small and you’ve spent sixty grand and put up with months of mess for nothing. Too large and you’ve spent money you didn’t need to whilst making your house look odd compared to your neighbours.

The sensible approach involves thinking about five things together, not just picking the biggest extension you can afford.

1. Working Out What Space You Actually Need

Start With How You Really Live

The first question isn’t “how big can we go?” but rather “what are we actually trying to fix?” For a family in Knowle or Dorridge knocking through their kitchen and dining room, the real question is what size lets them cook, eat, and sit down without it feeling like an aircraft hangar that costs a fortune to heat.

Questions worth asking yourself honestly:

How does your family actually use rooms day to day?
What specific things can’t you do now that drive you mad?
How many people need to be in the kitchen at the same time?
Do you genuinely have people round for dinner every week, or is that wishful thinking?
What will you need in five or ten years when the kids are older?

Think about the morning rush. Can three people get breakfast without bumping into each other? When you’re cooking dinner, can someone else make a cup of tea without getting in your way? These practical questions matter more than abstract square metres.

Space Requirements That Actually Work

Kitchen extensions need certain minimum sizes to be worthwhile:

Just a bigger kitchen: 15 to 20 square metres minimum
Kitchen with space to eat: 25 to 35 square metres
Kitchen, dining table, and somewhere to sit: 40 to 55 square metres
Full-width extension with proper zones: 50 to 70 square metres

These aren’t random numbers. They’re based on actually fitting in a proper kitchen that’s 2.4 to 3 metres wide, a dining table where people aren’t sitting with their elbows touching, and a sofa where you’re not on top of the cooker.

In Solihull and Warwick, houses vary enormously in size. A 45 square metre extension might look perfect on a big Victorian villa in Warwick but would completely overwhelm a modest 1930s semi in Shirley.

Does It Actually Work?

Before you commit to a size, check whether it genuinely functions:

Can you put furniture where it makes sense, not just squeeze it in?
Can you walk through without doing awkward sideways shuffles?
Can two people cook whilst the kids do homework at the table?
Does the kitchen triangle actually work?
Is there proper storage or will you need wall units everywhere?

These practical questions determine whether your extension becomes the heart of your home or an expensive mistake.

2. Making Sure It Suits Your House and Street

Does It Look Right On Your House?

Your extension needs to look right on your actual house. An extension that looks beautiful in isolation but overwhelms your property rarely adds the value you’d hope for.

Victorian and Edwardian houses around Solihull and Warwick:

These substantial buildings can take generous extensions. Single-storey rear extensions of 4 to 6 metres depth work well. Full-width extensions maintain the imposing presence these properties have. Two-storey extensions usually shouldn’t be more than half the size of the original house.

1930s semis in Knowle, Bentley Heath, and Dorridge:

These need a lighter touch. Extensions going back 3 to 5 metres usually look proportionate. Side returns work brilliantly, wrapping around the side to create L-shaped extensions that feel generous whilst respecting proportions.

Modern houses:

Often suit bolder, more contemporary extensions. Clean lines and simple shapes can handle larger additions. Think about how the extension works with the whole house’s design.

What About Your Neighbours?

Your extension doesn’t exist in isolation. Streets around Solihull and Warwick usually have houses that share similar sizes and styles, creating a harmony that people value.

An extension significantly bigger than what your neighbours have can:

Make your house look over-developed
Cause planning headaches even within permitted development
Potentially affect value if it feels out of place
Upset neighbours by blocking light or views

On the other hand, an extension that respects what’s around it whilst giving you the space you need shows proper thought. That’s something buyers appreciate.

3. Working Out the Money Side of Things

What Extensions Actually Cost

In Solihull and Warwick, for decent quality work, you’re looking at £2,200 to £3,500 per square metre in 2025, depending on what you want, how complicated it is, and what your site’s like.

Cost breakdown by type:

Basic single-storey rear extension: £2,200 to £2,500 per square metre
High-spec single-storey with bi-folds and roof lights: £2,500 to £3,500 per square metre
Two-storey extensions: £1,800 to £2,500 per square metre (economies of scale)
Side return extensions: £2,000 to £3,000 per square metre (often fiddly due to narrow access)

These are realistic figures for 2025, excluding VAT.

The Point Where Bigger Stops Being Better Value

The increase in your house’s value from an extension isn’t a straight line. There’s an optimal size beyond which adding more metres adds progressively less value.

Recent research from Nationwide Building Society shows that home improvements which add floor area can increase property value by up to 25% in the best cases. Single-storey extensions typically add 5% to 10%. An extra bedroom adds around 13%, whilst an extra bathroom adds roughly 4%.

Investment analysis for a typical Solihull house worth £380,000:

20 square metre extension at £50,000 to £55,000: adds roughly £60,000 to £75,000 value (excellent return)
35 square metre extension at £85,000 to £105,000: adds roughly £95,000 to £120,000 value (strong return)
55 square metre extension at £135,000 to £165,000: adds roughly £115,000 to £145,000 value (reasonable return)
75 square metre extension at £185,000 to £225,000: adds roughly £135,000 to £165,000 value (diminishing return)

The sweet spot for most family homes sits in the 30 to 45 square metre range. It creates genuinely transformative space whilst maintaining strong return on what you’ve spent.

When Going Bigger Makes Sense Financially

Larger extensions deliver better returns when:

Your house is already one of the bigger ones on the street
You’re creating really desirable features like master suites or annexes
You’re in premium locations where bigger houses command serious premiums
You’re planning to stay long-term and lifestyle benefits matter more

For a big detached house in Dorridge or Balsall Common worth £650,000 plus, a 60 square metre two-storey extension creating a master suite and enlarged kitchen can add £100,000 to £130,000 whilst genuinely transforming how you live.

4. Planning Rules and How Big You Can Go

Understanding Permitted Development

Most extensions in Solihull and Warwick can go ahead under permitted development rights, but there are strict size limits.

Single-storey rear extensions:

Detached houses: maximum 4 metres beyond the rear wall
Semi-detached and terraced houses: maximum 3 metres beyond the rear wall
Maximum height of 4 metres
Eaves height no higher than 3 metres if within 2 metres of a boundary

Two-storey and first-floor rear extensions:

Maximum 3 metres beyond the rear wall
Can’t be higher than the existing roof
Side walls must be at least 7 metres from the boundary

Side extensions:

Single-storey only under permitted development
Maximum half the width of the original house
Can’t stick out beyond the front wall

The Larger Home Extension Scheme

If you want to go bigger, the Larger Home Extension scheme lets you extend up to 6 metres for semi-detached or terraced houses, or 8 metres for detached houses. This requires prior approval and involves neighbour consultation, but it’s less onerous than full planning permission.

When You Need Planning Permission

Planning permission is required when:

Your extension goes beyond permitted development limits
Your house is in a conservation area (tighter restrictions apply)
Your house is listed (you need listed building consent)
You’ve already used your permitted development rights

Working with builders who know Solihull Metropolitan Borough and Warwick District planning inside out makes navigating this considerably easier.

5. Room Sizes That Actually Function

Kitchen Dimensions That Work

The kitchen bit of your extension needs specific minimum sizes to actually function properly.

Minimum kitchen dimensions:

Kitchen width: 2.4 metres absolute minimum, 2.7 to 3.0 metres comfortable
Kitchen length: 3.0 metres minimum for basic layout, 3.6 to 4.2 metres for optimal functionality
Space for island: 3.0 metres width minimum, 3.3 metres comfortable
Walking space around island: 1.0 to 1.2 metres on all sides

A kitchen zone of 12 to 15 square metres is the bare minimum for modern family living. Decent kitchens in Solihull and Warwick usually take up 18 to 25 square metres.

Dining Area Standards

Dining areas need enough space for people to sit comfortably and move around.

Dining area requirements:

Table for 6: 2.4 metres x 1.2 metres minimum
Table for 8: 2.7 metres x 1.2 metres minimum
Space around table for chairs and circulation: 1.0 to 1.2 metres on all sides
Minimum dining area: 12 to 15 square metres for 6 people, 16 to 20 square metres for 8 people

Living Zone Dimensions

The family living area needs proper space for comfortable furniture arrangements.

Living area requirements:

Minimum dimensions: 3.5 metres x 3.5 metres
Comfortable dimensions: 4.0 metres x 4.5 metres
Space for standard sofa: 2.2 metres length minimum
Walking space around furniture: 0.8 to 1.0 metres

How It All Works Together

The best extensions create distinct but connected zones. A 45 square metre extension might allocate 18 square metres to kitchen, 15 square metres to dining, and 12 square metres to living. This creates genuinely functional spaces rather than one big room where everything clashes.

Common Sizing Mistakes and What They Cost You

Mistake One: The Extension That’s Too Small

The most expensive mistake is building an extension that’s too small to actually solve your space problems. You’ve spent £60,000 to £80,000, endured months of disruption, and when it’s finished you still feel cramped.

The solution: Add 15% to 20% to your initial size estimates. The extra cost of slightly more space is modest compared to the cost of getting it wrong.

Mistake Two: The Show-Off Extension

The opposite mistake is building an extension that overwhelms your house or looks odd compared to your street. This often comes from architect-designed schemes that prioritise making a statement over sympathetic integration.

The solution: Design something that feels like a natural evolution of your house, not an architecture competition entry.

Mistake Three: Ignoring Ceiling Heights

Focusing only on floor area whilst accepting minimum ceiling heights creates spaces that feel mean regardless of square metres. Standard 2.4 metre ceiling heights feel adequate at best. Good extensions have 2.7 to 3.0 metre ceiling heights.

Investment perspective: Increasing ceiling height from 2.4 to 2.7 metres adds roughly £2,000 to £3,000 to a 40 square metre extension but dramatically improves how good it feels.

Mistake Four: Cheaping Out to Hit a Budget

Choosing a bigger extension with economy specifications rather than a slightly smaller extension with quality specifications rarely represents good value. In Solihull and Warwick, buyers notice and value quality. An extra 5 square metres with basic finishes adds less perceived value than brilliant finishes in a well-proportioned space.

Design Considerations for Different House Types

Victorian and Edwardian Villas

These substantial houses throughout Solihull and Warwick can accommodate generous extensions whilst maintaining their proportions. Single-storey rear extensions of 5 to 6 metres depth create substantial living spaces whilst respecting the imposing rear elevation. Full-width extensions maintain symmetry and scale.

1930s Semi-Detached Houses

The most common house type across Knowle, Dorridge, and Bentley Heath needs a considered approach. Extensions of 3.5 to 4.5 metres depth usually look proportionate whilst delivering 30 to 40 square metres of extra space. Side returns work brilliantly, creating L-shaped extensions that feel generous whilst respecting proportions.

Modern Family Homes

Contemporary houses suit extensions that work with modern design language. Clean geometric forms can handle bolder extensions. Flat roofs with roof lights work well. Think about how the extension relates to the whole property rather than just adding space.

The Use Your Space Approach to Sizing

At Use Your Space, we’ve developed a straightforward method for working out optimal extension size based on decades of experience across Solihull, Warwick, and surrounding areas.

Our Sizing Process

We start by understanding how your family genuinely lives and what improvements matter most. We assess your house’s proportions, style, and relationship to neighbouring properties. We provide clear cost projections and likely value impacts for different size options, enabling informed decisions balancing investment and lifestyle improvement.

Understanding Local Context

Our extensive experience means we understand what sizing works for different house types and locations. We know what’s typical in Knowle versus Shirley, what planning officers expect in Warwick’s conservation areas, and what buyers in Dorridge value. This local knowledge ensures your extension feels appropriate for its context whilst maximising usable space and investment return.

Making Your Sizing Decision

The right size extension balances five interconnected factors: genuine lifestyle requirements, property proportions, financial optimisation, planning regulations, and functional room dimensions.

Key Principles for Optimal Sizing

Start with function, not footprint

Work out what activities and furniture the space must accommodate, then determine the size required to achieve this comfortably.

Respect proportions

An extension should enhance your house’s presence, not overwhelm it.

Prioritise quality over quantity

A beautifully executed 35 square metre extension with premium specifications typically adds more value than a basic 50 square metre extension.

Consider future buyers

Design something that will appeal to the buyers your property will eventually attract.

Build in flexibility

Spaces that can adapt to changing needs deliver better long-term value.

Your Next Steps

Working out the right size extension for your Solihull or Warwick property requires balancing multiple factors. The investment in getting this decision right pays dividends both in immediate lifestyle improvement and long-term property value.

Ready to explore how a lhome extension could enhance your Solihull or Warwick home? Contact Use Your Space today for an initial consultation. We’ll visit your property, discuss your aspirations, assess the possibilities, and provide honest advice about what’s achievable and what returns you might expect.

Our comprehensive approach means we handle every aspect from initial design through planning (if required), building regulations, and construction to final completion. Transform your unused home for your your family needs whilst enhancing your property’s value.

Contact Use Your Space today to begin your loft conversion journey across Solihull, Warwick, Knowle, Dorridge, Bentley Heath, Shirley, Balsall Common, Leamington Spa, and Kenilworth.