Quick Summary

The Single Storey Extension Cost in 2025 depends on several key factors such as location, design complexity, materials, and the quality of finish you choose. Prices have continued to rise due to increased labour and material costs, especially in high-demand regions like London and the South East. To get a realistic estimate, homeowners should also factor in professional fees, contingency allowances, and VAT when calculating the full project cost.

Why 2025 Costs Remain Elevated

Construction costs haven’t fallen back to pre-2020 levels.
Material prices (timber, steel, concrete) and skilled labour remain high across 2025 due to inflation lag and energy-driven manufacturing costs.
Indices from Homebuilding, BuildPartner, and BCIS show sustained elevation of 10–15% above 2023 levels.

Translation: prices won’t crash — lock in quotes early, use fixed-price contracts, and carry at least a 10–12.5% contingency.

Average Single Storey Extension Cost per m² (2025)

In 2025, single storey extension cost in 2025 continues to be driven by high material and labour inflation, with average build-only figures hovering between £2,200 and £3,300 per m² across the UK (before VAT and hidden extras). London and the South East push toward the upper end (or beyond) of that range, thanks to premium glazing, demanding site logistics, and skilled labour scarcity. Always budget for professional fees (≈ 10–15 %), a contingency buffer (10–12 %), and the inevitable VAT uplift if your extension doesn’t fall into a reduced-rate scheme.

Region	Standard Spec	High Spec	Notes
Nationwide Average	£2,200–£3,000/m²	£3,000–£3,300/m²	Most 2025 midrange builds
London & SE	£2,400–£3,500+/m²	£3,600–£4,000/m²	Premium labour + glazing-heavy
Northern England / Midlands	£2,000–£2,700/m²	£2,700–£3,000/m²	Lower labour, smaller sites

Single story extension cost in 2025 Examples

Size	Low Spec (£2,200/m²)	Mid Spec (£2,800/m²)	High Spec (£3,300/m²)
15 m²	£33,000	£42,000	£49,500
20 m²	£44,000	£56,000	£66,000
25 m²	£55,000	£70,000	£82,500
30 m²	£66,000	£84,000	£99,000

The Real Single Storey Extension Cost in 2025or Single Storey Extension Cost (Full Project Stack)

When planning your home improvement, understanding the Single Storey Extension Cost in 2025 means looking beyond just the build price. The real budget includes every layer of the project — from design and planning fees to structural work, finishes, and final approvals. Rising labour and material costs across the UK, especially in London and the South East, make accurate budgeting essential. Always factor in professional fees, contingency funds, and VAT to get a true picture of your full project cost.

Don’t stop at build cost — these extras bite.

Item	Typical Range	Notes
Professional Fees	10–15%	Architect, structural engineer, building regs
Planning & Compliance	£1,000–£3,000	LDC, prior approval, party wall, building control
Contingency	10–12.5%	For unforeseen issues
VAT	Usually 20%	Unless energy-saving or conversion applies
Utilities / Upgrades	£2,000–£5,000	Drainage, electrics, boiler upgrade

Example total for Single Storey Extension Cost in 2025 (20 m² mid spec):
Build £56,000 + fees £7,000 + contingency £6,000 + VAT £13,800 → ~£82,800 all-in

Types of Single-Storey Extensions (2025) — Rated & Compared

When comparing options, the Single Storey Extension Cost in 2025 varies widely depending on the type and complexity of the design. A simple rear extension remains the most affordable route to add living space, while side-return and wraparound extensions typically cost more due to structural work and bespoke layouts. Contemporary glass or open-plan designs can elevate both the look and value of your home but come with higher material and glazing costs. Choosing the right type depends on your budget, property layout, and long-term goals.

Type	Description	Typical Cost	Build Complexity	Planning Difficulty	Value-for-Money	Honda’s Verdict
Rear Extension	Straight rear projection into the garden	£2,200–£3,000/m²	🟢 Low	🟢 Easy (PD up to 3–4 m)	🟢🟢🟢🟢	Top pick: efficient, high ROI
Side Return	Fills side alley of period houses	£2,400–£3,300/m²	🟠 Medium	🟠 Moderate	🟢🟢🟢	Smart urban gain, minor planning
Wrap-Around (L-Shape)	Combines rear + side	£2,800–£3,600/m²	🔴 High	🔴 Full planning	🟢🟢🟢🟢	Great space, expensive complexity
Lean-To / Flat Roof	Simple sloped or flat roof	£2,000–£2,700/m²	🟢 Low	🟢 Easy	🟢🟢🟢🟢🟢	Budget hero
Pitched / Gable Roof	Roof matches main house	£2,400–£3,300/m²	🟠 Medium	🟠 Some limits	🟢🟢🟢🟢	Classic and resale-friendly
Glass Pavilion / Modern Glazed	Structural glazing, roof lanterns	£3,200–£4,500+/m²	🔴 Very High	🔴 Hard	🟠🟠🟠	Luxury look, luxury price
Double-Storey Add-On	Adds one level above extension	£2,700–£3,800/m²/floor	🔴 High	🔴 Always needs planning	🟢🟢🟢	Best £/m² long-term
Conservatory / Orangery	Mix of solid + glazed	£1,900–£2,700/m²	🟢 Low	🟢 Easy	🟢🟢🟢	Good light, mid-quality feel

✅ Summary:

Rear = best ROI
Wrap-around = premium impact
Lean-to = cheapest
Glass pavilion = design statement
Side return = compact, perfect for city terraces

Planning & Permitted Development (PD) in 2025

Understanding how planning rules apply to your project is just as important as knowing the Single Storey Extension Cost in 2025. Many extensions can still fall under Permitted Development (PD) rights, allowing you to build without a full planning application — provided you meet specific size, height, and boundary limits. However, with recent updates to building and energy regulations, it’s wise to check with your local authority or architect before starting. Clear planning from the outset helps avoid costly delays and ensures your extension meets current 2025 standards.

✅ What You Can Usually Build Without Full Planning

Terraced / Semi-detached: extend 3 m from rear wall
Detached: extend 4 m from rear wall
Larger Home Extension (Prior Approval): up to 6 m (terraced/semis) or 8 m (detached)

Height limits:

Max 4 m overall; eaves ≤ 3 m within 2 m of boundary
Materials must be similar to existing property
Must not cover more than 50% of the total garden/curtilage

🏛️ Always apply for a Lawful Development Certificate (LDC) — it legally confirms your build is compliant.
https://www.gov.uk/guidance/lawful-development-certificates

⚠️ You’ll need Full Planning Permission if:

You’re combining side + rear (wrap-around)
You live in conservation areas or listed buildings
You’re close to a highway or boundary with complex heights

Planning Portal:
https://www.planningportal.co.uk/planning

Factors That Push Costs Up

Large steel goalpost frames for open spans
Poor ground or drainage reroutes
Limited access (terraced properties)
Structural glazing or oversized sliders
Premium roof finishes or microcement floors
London/SE labour rates
Design revisions mid-build

How to Keep Costs Under Control

Design to a budget ceiling, not the other way around.
Limit glazing ratio — big glass = big cost.
Stick with flat or lean-to roofs for simplicity.
Use standard aluminium over minimal-frame sliders.
Choose porcelain or vinyl floors instead of microcement.
Fix prime cost (PC) sums in contract for kitchen/bath.
Keep a 10–12.5% contingency untouched until sign-off.

Typical Timeline (2025)

Stage	Duration	Description
Design & Surveys	2–4 weeks	Concept + measured survey
Planning / Prior Approval	4–8 weeks	Depends on council
Technical Design / BC	2–3 weeks	Building regs drawings
Contractor Tender & Start	2–3 weeks	Quotes + mobilization
Construction	8–14 weeks	Foundations → roof → finishes
Snag & Completion	1–2 weeks	Handover + sign-off

Single storey extension cost in 2025 FAQs

The Single Storey Extension Cost in 2025 is one of the most common questions homeowners ask when planning to expand their living space. Costs can vary depending on size, design, materials, and location, but understanding the key factors behind pricing helps you plan realistically. Below are the most frequently asked questions about single storey extension costs, planning rules, and what to expect during the build process.

How much does a single-storey extension cost per m² in 2025?
£2,200–£3,300/m² nationwide; £2,400–£3,500+ in London (ex-VAT).

How much does a 20 m² extension cost?
£44,000–£66,000 build-only; around £80,000–£90,000 fully loaded.

Do I need planning permission?
Often no — if within 3–4 m depth (PD). Larger (6–8 m) needs Prior Approval. Wrap-around always needs planning.

What’s the cheapest type?
Lean-to or flat roof rear extensions — simple, PD-friendly, quick.

Which adds the most value?
Wrap-around or large rear kitchen extensions — strongest impact on resale.

Conclusion — What It All Means for 2025

Building a single storey extension cost in 2025 isn’t cheap, but it remains one of the best-value investments you can make in your home. The Single Storey Extension Cost in 2025 may vary depending on design, materials, and location, but it still offers excellent lifestyle and resale benefits — especially when planned smartly under Permitted Development rules.

The key to success is simple:
👉 Plan early,
👉 Fix your budget,
👉 Lock in prices,
👉 Use trusted professionals.

A well-executed rear or wrap-around extension can add 15–25% to your property’s value, while giving you a space built for modern living.

If you’re planning your own project, use our Extension Cost Calculator and get accurate estimates from Builder Expert’s specialists — so you can move forward with confidence, not guesswork.

🔗 Related Reading — Builder Expert B

Explore more in-depth guides on the Builder Expert Blog to help you plan your next project with confidence. From construction costs and building regulations to planning permission and home improvement tips, our latest articles break down everything you need to know beyond just the Single Storey Extension Cost in 2025.