How Much Does a Home Extension Cost?

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How Much Does A Home Extension Cost? What To Expect In 2025

So, your home is starting to feel a little too small. Maybe the kids need their own rooms, your kitchen feels cramped, or you’re working from the dining table and dreaming of a proper office. Instead of moving (and paying estate agent fees, stamp duty, and dealing with the stress), a home extension could be the answer.

But how much will it cost? And more importantly, how do you make sure you’re paying a fair price?

Let’s break it down, so you know exactly what to expect when planning your extension.

What Types of Extensions Are There?

Not all extensions are the same. The type of extension you choose will affect the overall cost. Here are the most common types:

  1. Single-Storey Extension – Adds extra space on the ground floor, such as a kitchen extension or a new lounge.
  2. Double-Storey Extension – Extends the house on both the ground and first floor, typically for extra bedrooms or a bigger upstairs living space.
  3. Side Extension – Built on the side of your home, often used to expand kitchens or add utility rooms.
  4. Rear Extension – Extends the back of the house, commonly used for open-plan living spaces.
  5. Wraparound Extension – A combination of a side and rear extension, wrapping around the house.
  6. Loft Conversion – Converts your attic into a liveable space, usually for a bedroom or office.
  7. Garage Conversion – Turns an existing garage into a room.

How Much Will It Cost? (UK Averages for 2025)

The cost of an extension depends on the size, materials, and complexity of the build. Below are rough price estimates per square metre:

Type of Extension Cost per Square Metre (£) Estimated Total Cost (£)
Single-Storey £1,900 – £3,000 £38,000 – £60,000 (20m²)
Double-Storey £1,500 – £2,500 £60,000 – £100,000 (40m²)
Side Extension £1,500 – £2,400 £22,500 – £36,000 (15m²)
Rear Extension £1,200 – £1,800 £30,000 – £37,500 (25m²)
Wraparound £2,500 – £3,500 £75,000+
Loft Conversion £1,500 – £2,000 £30,000 – £50,000
Garage Conversion £1,000 – £1,500 £10,000 – £20,000

These are general estimates, your final cost will depend on the design, location, and materials you choose.

Where Is My Money Going? (Cost Breakdown)

Building an extension isn’t just about bricks and mortar. Here’s a rough guide to where your money goes:

1. Labour Costs (40-50%)
  • Builders, plasterers, electricians, plumbers, and decorators.
  • Skilled labour is one of the biggest costs, but good work saves you money in the long run.
2. Materials (30-40%)
  • Bricks, timber, cement, insulation, windows, roofing.
  • Basic materials cost less; premium finishes (e.g., bifold doors, underfloor heating) increase costs.
3. Professional Fees (10-15%)
  • Architects, surveyors, and structural engineers.
  • Some designs require specialist input, adding to costs.
4. Permissions and Regulations (5-10%)
  • Planning permission (if required).
  • Building regulation approval to ensure work meets UK safety standards.
5. Fixtures and Finishes (Varies)
  • Flooring, lighting, kitchen units, bathroom fittings.
  • These costs depend on personal choices—luxury finishes will push up the total price.

What Affects the Final Cost?

Even with the estimates above, your total cost can change based on:

1. Design Complexity
  • Simple rectangular extensions are cheaper.
  • Complex designs, custom-built features, or curved walls increase costs.
2. Choice of Materials
  • Standard bricks and UPVC windows cost less.
  • Natural stone, timber cladding, or aluminium windows increase costs.
3. Location
  • Extensions in London and the South East cost up to 20-30% more due to higher labour and material costs.
  • Rural areas might have lower costs but could face higher transport fees for materials.
4. Site Conditions
  • If your land is sloped or has drainage issues, extra work will be needed, adding to the final price.
5. Changes During the Build
  • If you decide mid-project to change the design or upgrade materials, expect additional charges.

How Do I Know If My Quote Is Fair?

Before agreeing to any quote, follow these steps:

  1. Get At Least 3 Quotes – Compare prices from different builders to check for consistency.
  2. Check What’s Included – A cheap quote might leave out key parts (like VAT or flooring), leading to hidden costs.
  3. Ask About Payment Schedules – Never pay the full amount upfront. Reputable builders take staged payments.
  4. Look at Past Work – Read reviews, visit completed projects, and ask for references.
  5. Ensure the Builder is Accredited – Check if they’re part of the Federation of Master Builders (FMB) or TrustMark.

Other Costs to Keep in Mind

Apart from the building work itself, don’t forget these additional expenses:

  • Planning Permission (£200-£500) – Required for larger or more complex projects.
  • Building Regulations Approval (£500-£1,500) – Ensures your extension meets UK safety standards.
  • Structural Engineer Fees (£500-£2,000) – If your project requires major alterations.
  • Party Wall Agreement (£1,000-£2,000) – Needed if you’re building near a neighbour’s boundary.

Ways to Save Money on Your Extension

Want to keep costs down without cutting corners? Try these:

✅ Keep the Design Simple – Complicated designs cost more to build.
✅ Choose Cost-Effective Materials – Basic materials still offer durability and style.
✅ Plan Everything in Advance – Last-minute changes = extra charges.
✅ Do Some Work Yourself – Painting, decorating, and landscaping can save thousands.
✅ Avoid Peak Building Seasons – Builders are busiest in summer, so you may get better rates in autumn or winter.

Final Thoughts: Is a Home Extension Worth It?

A home extension is a big investment, but when done right, it adds value to your property and improves your quality of life.

If you’re ready to explore your options, JP Hallam offers free, no-obligation quotes and expert guidance to help you create the perfect extension without the stress.

Got questions? Need a quote? Contact us today!

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