If you’re asking yourself, “How can I reduce the cost of building an extension?”, you’re not alone. With material and labour prices on the rise, homeowners across the UK are seeking smart, effective ways to keep their extension projects within budget—without sacrificing quality. At KT5 Construction, we specialise in helping you build beautiful, functional spaces affordably. In this blog, we share expert-backed strategies to save money and make the most of your investment.

Plan Meticulously from the Start

Why Planning Ahead Matters

One of the most effective ways to cut costs is to plan thoroughly before construction begins. Making changes mid-project often leads to delays and additional costs. Detailed planning ensures clarity around the scope, materials, and design, reducing the chance of unexpected expenses later.

Pro Tip: Lock down your layout and materials during the concept stage. Changes made at later RIBA stages can trigger redesign fees, planning re-approvals, and contractor variations.

Keep Designs Simple and Efficient

Avoid Overly Complex Layouts

The more straightforward the design, the more budget-friendly your extension becomes. Opt for clean lines, simple roof shapes, and a modest footprint. Avoid excessive glazing or awkward configurations that require expensive structural solutions.

Example: A lean-to rear extension can offer fantastic functionality with a lower build cost compared to multi-angle or wraparound layouts.

Choose Standard Materials and Fixtures

Modify Instead of Customising

Bespoke features look great, but they come at a premium. Use off-the-shelf components wherever possible. Modify standard kitchen units or furniture to match your style instead of commissioning made-to-measure pieces.

Example: Use Ikea or Howdens base units with custom doors for a high-end look at a fraction of the price.

Source Items Yourself

Client-Supplied Materials

If you’re comfortable taking on some responsibility, consider supplying items like kitchens, flooring, or sanitaryware. This avoids contractor mark-ups that can add 10–20% to material costs.

Note: Be prompt with delivery and quantity accuracy to avoid delays and additional charges.

Limit Structural Changes

Retain Existing Walls and Services

Knocking down internal walls or moving plumbing dramatically increases labour and materials costs. Retain layouts where possible and design the extension to integrate with existing service locations.

Savings Tip: Keeping kitchens and bathrooms in their original positions saves significant plumbing and groundwork expenses.

Reuse Existing Materials

Sustainable and Budget-Friendly

Reclaim materials during demolition, such as bricks, timber, or tiles. These can be reused or resold, saving you money and reducing landfill waste.

Example: Original bricks can be used for garden walls or landscaping, while timber floors can be sanded and reused.

Work with the Right Team

Hire Trusted Contractors and Professionals

Choosing a reputable builder and experienced architect or Quantity Surveyor (QS) helps avoid budget overruns. A reliable team prevents mistakes, manages risks, and ensures accurate payment valuations.

Pro Tip: Don’t just go for the cheapest quote. Instead, analyse tenders carefully for hidden costs or exclusions.

Consider Phased Construction

Split the Project

If budget is tight, split the project into phases. Complete the essential structure first, and defer landscaping, interior finishes, or secondary rooms to later stages.

Warning: While this provides short-term savings, costs per square metre may increase due to reduced economies of scale.

Frequently Asked Questions

1. Is it cheaper to build up or out?

Generally, two-storey extensions are more cost-efficient per square metre than single-storey ones.

2. Can I save by project managing myself?

Yes, but only if you have time and experience. Mismanagement can lead to costly mistakes.

3. Should I move out during construction?

Yes. This helps contractors work more efficiently and may reduce your labour costs.

Final Thoughts

Reducing the cost of building an extension requires strategic decisions, smart design, and the right team. At KT5 Construction, we guide you through every step with transparency and expertise, helping you bring your vision to life—on time and on budget.

Ready to save on your extension project? Contact KT5 Construction today for a free consultation and get expert advice tailored to your home.