Single-Storey vs Double-Storey Extension: Which Is Right for Your Home?

When you’re planning a house extension, one of the biggest decisions is whether to go single-storey or double-storey. Both have distinct advantages — but they also differ significantly in cost, planning complexity, space gain, and return on investment.

This guide breaks down the key differences, helping you make an informed decision that’s right for your home, your budget, and your lifestyle.

Single-Storey Extensions: The Essentials

A single-storey extension adds one level of living space, typically extending from the rear or side of your home. It’s the more common choice for house extensions across Nuneaton and Warwickshire.

Typical Uses for Single-Storey Extensions

• Kitchen extensions: Open-plan kitchens with dining areas are the most popular use
• Living space: Additional lounge or family room
• Playrooms or home offices: Ideal for working-from-home setups
• Utility rooms: Larger laundry and storage spaces
• Sunrooms or garden rooms: Bringing outdoor living indoors

Cost of Single-Storey Extensions

Single-storey extensions are generally the most affordable extension option:

• Typical cost range: £1,500–£3,000 per square metre
• Small extension (15 m²): £22,500–£45,000
• Medium extension (25 m²): £37,500–£75,000
• Larger extension (40 m²): £60,000–£120,000

These figures are approximate and vary based on:

• Specification and finish quality
• Foundation and ground conditions
• Structural complexity
• Location (Nuneaton prices are competitive compared to London or the South East)

Planning Permission for Single-Storey

This is where single-storey extensions shine. Most qualify for permitted development, meaning:

• No planning application needed (in most cases)
• Faster process: Build can start sooner
• Lower professional fees: No planning consultant or architect required
• Fewer council delays: No 8-week waiting period for approval

However, you still need building regulations approval, which is non-negotiable.

Advantages of Single-Storey Extensions

✓ Lower cost: Least expensive extension option
✓ Easier planning: Most qualify for permitted development
✓ Faster build: Typically 8–12 weeks
✓ Less disruption: Simpler construction process, smaller footprint
✓ Good light and space: Open-plan designs work beautifully with single-storey
✓ Suitable for most properties: Works on detached, semi-detached, and terraced homes (with conditions)
✓ Lower maintenance: Fewer roof lines and structural complexities

Disadvantages of Single-Storey Extensions

✗ Limited space gain: You gain horizontal space, not vertical
✗ Garden loss: Extends further into the garden to maximise living area
✗ Less value uplift: Modest return on investment compared to two-storey
✗ Headroom: Eaves can feel restrictive if ceilings are low
✗ Less suitable for larger families: Limited bedrooms

Double-Storey Extensions: The Essentials

A double-storey extension adds two levels of living space — typically creating an additional bedroom and bathroom upstairs, with expanded kitchen or living space below.

Typical Uses for Double-Storey Extensions

• Additional bedrooms: Second, third, or fourth bedroom with en-suite
• Family homes growing: Couples with young children planning for more space
• Multi-functional spaces: Ground floor for living, first floor for private bedrooms
• Maximising value: Highest ROI of all extension types
• Narrow properties: Makes efficient use of limited garden depth

Cost of Double-Storey Extensions

Double-storey extensions are significantly more expensive than single-storey:

• Typical cost range: £2,200–£3,500 per square metre
• Small double-storey (30 m²): £66,000–£105,000
• Medium double-storey (45 m²): £99,000–£157,500
• Larger double-storey (60 m²): £132,000–£210,000

The higher cost reflects:

• Additional structural complexity (two storeys require stronger foundations and walls)
• More roof area and structural elements
• Additional plumbing, electrical, and heating systems
• Greater building regulations scrutiny
• Longer construction time (more labour, more inspections)

Planning Permission for Double-Storey

This is where double-storey gets tricky. Most require formal planning permission:

• Permitted development is very limited: Only works under strict conditions
• Planning application required: In most cases, you’ll need to apply to the council
• 8-week decision period: Standard timeline (can extend if council requests more information)
• Neighbour consultations: Council may consult neighbours; objections can delay or block the project
• Conservation area restrictions: Much tighter rules in conservation areas (common in Nuneaton)
• Professional fees: Architect and planning consultant costs add £2,000–£5,000+

Advantages of Double-Storey Extensions

✓ Maximum space gain: Two levels means significantly more living area
✓ Best for bedrooms: Creates additional bedrooms (major value driver)
✓ Preserves garden: Minimal garden impact compared to single-storey of equivalent floor area
✓ Best ROI: Highest return on investment (typically 20–25% value uplift)
✓ Future-proof: Growing families often stay longer because of extra space
✓ Better proportions: Two storeys often look more balanced on the house
✓ Rental appeal: Extra bedrooms attract premium rental income

Disadvantages of Double-Storey Extensions

✗ Significantly higher cost: £25,000–£40,000 more expensive than single-storey
✗ Planning permission usually needed: Delays and uncertainty; potential for refusal
✗ Longer build time: Typically 16–24 weeks
✗ Neighbour objections: Risk of complaints about loss of light or privacy
✗ More complex build: Greater structural demands, more building regulations inspections
✗ Greater disruption: Longer site presence, more noise and activity

Cost Comparison: Side-by-Side

Let’s compare a typical single-storey vs double-storey extension for a semi-detached home in Nuneaton:

Single-Storey Rear Extension (25 m²)

Item	Cost
Construction	£50,000
Building Regulations (no planning)	£1,500
Architect/designer fees	£800
Total	~£52,300
Timescale	8–12 weeks

Double-Storey Rear Extension (45 m²)

Item	Cost
Construction	£130,000
Planning application & consultant	£3,500
Building Regulations	£2,500
Architect/structural engineer	£4,000
Total	~£140,000
Timescale	20–28 weeks

The difference: A double-storey costs roughly 2.7x more and takes 2–3x longer — but gains you nearly double the floor area and, often, a significant bedroom uplift.

Planning Implications: A Critical Comparison

Single-Storey Planning

• Permission needed? Usually no (permitted development)
• Council application? No
• Timescale: 1–2 weeks for building regulations approval
• Neighbour risk: Minimal (general notifications, but few objections)
• Cost: None (no planning fees)

Double-Storey Planning

• Permission needed? Usually yes
• Council application? Yes, detailed application required
• Timescale: 8 weeks minimum (can be 16+ weeks if objections arise)
• Neighbour risk: High (formal neighbour consultations; objections common)
• Cost: £500–£1,000+ application fee + £2,000–£5,000 professional fees

Space Gained: What You Actually Get

Single-Storey Extension (25 m²)

Typical layout:
– Open-plan kitchen/diner (15 m²)
– Utility room (5 m²)
– Hallway/circulation (5 m²)
– Result: One large, connected living space

Double-Storey Extension (45 m²)

Typical layout:
– Ground floor (25 m²): Expanded kitchen, dining, living area
– First floor (20 m²): New bedroom (4x4m) + new bathroom/en-suite
– Result: Significantly more overall space plus a new bedroom

Return on Investment (ROI): Which Adds More Value?

This is crucial for many homeowners. Does the extra cost translate to higher property value?

Single-Storey Extension ROI

• Typical value uplift: 15–20% of extension cost
• Example: £50,000 extension adds ~£7,500–£10,000 value
• Why modest?: Single-storey doesn’t add bedrooms; perceived as luxury rather than essential

Double-Storey Extension ROI

• Typical value uplift: 20–25% of extension cost
• Example: £130,000 extension adds ~£26,000–£32,500 value
• Why better?: Additional bedroom significantly appeals to families; perception of “proper” house expansion

Key insight: Double-storey’s ROI is better percentage-wise, but single-storey typically returns faster because there’s less absolute cost to recover.

Long-Term Value

• Single-storey: Adds modest value quickly; useful for immediate lifestyle improvement
• Double-storey: Takes longer to recover cost, but creates more fundamental value; better for long-term ownership

Which Should You Choose?

Choose Single-Storey If:

• Budget is limited: You want maximum improvement for minimum cost
• You don’t need extra bedrooms: Your family size is stable or small
• You want speed: You want the work done quickly with minimal planning hassle
• You have a good-sized garden: You don’t mind extending further back
• You want the easiest planning route: Permitted development is simpler
• You’re not planning to sell soon: You won’t worry about ROI

Choose Double-Storey If:

• You need extra bedrooms: Growing family or desire for guest space
• You want maximum value uplift: You’re thinking about future resale
• You have limited garden depth: A narrow property where extending far back isn’t ideal
• You’re planning long-term ownership: 10+ years, so build cost recovery matters less
• You can manage the planning process: You’re willing to navigate council applications
• Budget allows: The extra £50,000–£100,000 is within reach

The Role of Your Property Type

Detached Homes

• Single-storey: Very easy planning; maximise garden use
• Double-storey: Excellent choice; few neighbour concerns; very appealing

Semi-Detached Homes

• Single-storey: Standard permitted development rules
• Double-storey: Doable, but neighbour concerns more likely (shared boundary)

Terraced Homes

• Single-storey: More restrictive permitted development rules; planning often needed
• Double-storey: Planning almost always needed; neighbour impact is significant

Conservation Areas

• Single-storey: May need planning permission (Article 4 Direction likely)
• Double-storey: Almost always needs planning; stricter criteria applied

How Parker Grears Helps You Decide

At Parker Grears Developments Ltd, we’ve managed dozens of extensions — both single and double-storey — across Nuneaton, Hinckley, and Warwickshire. We help you make the right choice by:

• Understanding your needs: Space requirements, timeline, budget
• Assessing planning feasibility: Early honest advice on planning likelihood
• Comparing costs and ROI: Clear financial modelling so you understand the investment
• Managing the entire process: From design through to building regulations sign-off
• Delivering quality: FMB members, TrustMark certified, backed by 5/5 Google reviews

Our Quantity Surveyor service (£240 + VAT) includes:

• Site assessment and measurement
• Preliminary layout options (single vs double-storey)
• Cost estimation for each option
• Planning feasibility assessment
• Timescale comparison
• Clear recommendation based on your situation

Next Steps: Getting Started

If you’re unsure whether single or double-storey is right for your home, the best first step is a professional consultation. We’ll assess your property, understand your priorities, and guide you towards the right solution.

Ready to explore your extension options?

Contact Parker Grears Developments Ltd today:

Phone: 07731015784
Website: parkergrears.com

We’re FMB members, fully insured, and offer a no-pressure consultation. Let’s find the extension that’s perfect for your home and your life.