Cost of House Extensions in the North West (2025 Guide):
Single Storey, Two Storey, Garage and Loft Conversions
Introduction: Understanding Extension Costs in the North West
Cost of House Extensions
One of the most common questions I get from homeowners in Wigan, St Helens, and across the North West is:
“How much does a house extension actually cost?”
It’s an important question — but the truth is, no two projects are ever the same. As an architectural designer, I don’t get involved in the actual pricing of materials or builder quotes, because those costs can fluctuate significantly depending on location, demand, and specification.
However, what I can do is guide you through realistic averages and help you understand what factors affect extension prices, so you can plan your budget with confidence.
At Melrose Designs, we’ve supported hundreds of North West homeowners through the planning, design, and building regulations stages — and we know exactly what separates a cost-effective extension from a costly one.
🏡 Average Cost of House Extensions in the North West (2025)
Type of Extension Typical Cost Range (per m²) Average Total Cost Notes
- Single Storey Rear Extension £1,800 – £2,500 / m² £45,000 – £75,000 Most popular for open-plan kitchens & living spaces
- Two Storey Extension £2,000 – £2,800 / m² £70,000 – £120,000 Adds bedrooms & bathrooms; strong value boost
- Garage Conversion £12,000 – £25,000 — Great for home offices or utility rooms
- Loft Conversion (Dormer) £25,000 – £55,000 — Ideal for extra bedrooms or ensuites
- Wrap-Around Extension £2,400 – £3,000 / m² £90,000 – £140,000 Complex but maximises living space
💬 Costs are indicative for 2025 based on North West averages. Always obtain local builder quotations.
🧱 What Affects the Cost of Your Extension?
The final cost of your extension depends on several factors:
- Size and complexity – Larger or multi-storey builds naturally cost more.
- Specification and finishes – Premium glazing, kitchens or bathrooms raise budgets fast.
- Site conditions – Sloping ground, access issues or drainage changes increase labour costs.
- Structural design – Steel beams, foundation depth and wall construction all matter.
- Planning and building regulations – Design revisions or conditions can add professional fees.
At Melrose Designs, we create planning permission and building regulation drawings that allow your chosen builder to price accurately — saving you from mid-project surprises.
🔍 Example Project Costs (Realistic Scenarios)
Project Type Description Estimated Build Cost Typical Design Fee
Single Storey Kitchen Extension, Wigan 20 m² rear extension with bifold doors £45,000 – £55,000 £1,200 – £1,800
Two Storey Side Extension, St Helens Adds bedroom & ensuite £85,000 – £100,000 £1,800 – £2,400
Dormer Loft Conversion, Warrington Bedroom + ensuite £35,000 – £45,000 £1,200 – £1,800
Garage Conversion, Ormskirk Home office conversion £18,000 – £22,000 £900 – £1,200
🧩 Planning vs Building Regulations Costs
Planning drawings outline your design concept and are used to apply for planning permission.
Building Regulations drawings, on the other hand, detail how the extension will actually be built — including structure, insulation, and fire safety.
👉 Read our full guide: The Difference Between Planning Permission and Building Regs Drawings
🧠 Professional Insight: Why Early Design Pays Off
Having worked with dozens of homeowners across the North West, I’ve seen how early design planning saves both time and money. Builders give far more reliable quotes when they have detailed construction drawings.
At Melrose Designs, we focus on:
- Clear, buildable design solutions
- Cost-effective specifications
- Coordination with structural engineers
- Support through planning and building stages
This helps our clients stay within budget — without compromising on design quality.
💬 FAQs (Featured Snippet-Optimised)
1️⃣ How much does a single storey extension cost in the North West?
→ Between £1,800 – £2,500 per m², depending on finishes and access.
2️⃣ Is a two storey extension worth it?
→ Yes — it typically costs 50% more than a single storey but doubles usable space, offering better long-term value.
3️⃣ How much does a loft conversion cost in Wigan?
→ Dormer conversions average £30,000 – £45,000, depending on design and roof type.
4️⃣ Do I need planning permission for an extension?
→ Many single storey rear extensions fall under permitted development, but always check with your local planning authority.
5️⃣ Can I get a fixed-price design quote?
→ Yes — Melrose Designs offers transparent, fixed-price packages for both planning and building regulation drawings.
📍 Serving the North West with Trusted Design Expertise
Based in Wigan, we proudly serve:
- Greater Manchester
- St Helens
- Warrington
- Chorley
- Bolton
- Preston
We provide house extension design, loft conversion plans, and building regulations drawings tailored to your needs.
💬 Start your extension journey today — request your fixed-price design quote from Melrose Designs.
✍️ About the Author
Kieran Atherton — Director of Melrose Designs
Kieran is an experienced architectural designer based in Wigan, specialising in home extensions, loft conversions and building regulation drawings across the North West.
He’s helped hundreds of homeowners bring their design ideas to life, combining creative vision with technical accuracy.
🔗 Internal Links
Planning Permission vs Building Regulations Drawings