Building a home extension is one of the best ways to gain space, increase your property’s value, and improve your lifestyle without moving house. But if you’re unsure where to start, you’re not alone. This step-by-step guide from KT5 Construction explains how to begin, what to consider, and how to ensure your extension is completed on time and on budget.

Define the Purpose of Your Extension

What Are You Trying to Achieve?

Start by asking:

• • Do I need more space for my growing family?

  • Would an open-plan kitchen improve my daily life?

  • Do I need a ground-floor bedroom or home office?

Defining your goals early is essential to building a home extension that meets your needs.

Set a Realistic Budget

Include:

• • Build costs (£1,500–£2,500/m² in London)

  • Architectural and structural design fees

  • Planning and approval fees

  • Contingency for unexpected expenses

Understand Planning Rules

Do You Need Planning Permission?

Many rear and side extensions fall under Permitted Development Rights. However, larger projects or those near boundaries may require full planning permission.

Let KT5 Guide You

We offer:

• • Pre-application advice

  • Party Wall guidance

  • Building Regulations support

Our team ensures your project complies with local laws from day one.

Choose the Right Builder

Work With Trusted London Builders

When building a home extension, working with professionals is crucial. KT5 Construction provides:

• • Fixed-price quotes

  • Weekly project updates

  • Design-to-build coordination

We’ve helped hundreds of London and Surrey homeowners create beautiful, functional spaces—on time and on budget.

Avoid Costly Mistakes

Avoid builders who:

• • Provide vague estimates

  • Lack insurance or accreditations

  • Avoid written contracts

Get Your Design and Structure Right

Plans and Calculations

Before building starts, you need:

• • Architectural drawings

  • Structural calculations

  • Party Wall notices (if needed)

We include all these services in our design-and-build packages—making KT5 a cost-effective and efficient choice.

Begin the Build

Site Set-Up and Construction

Once designs are approved, we:

• • Set up the site safely

  • Manage schedules and trades

  • Keep you informed at every stage

A typical single-storey extension takes 10–16 weeks.

Living at Home During Works

Yes, in most cases. We minimise disruption by separating work areas and maintaining daily cleanliness.

Frequently Asked Questions

Q : How Much Does Building a Home Extension Cost?

Costs vary depending on size and location, but a well-managed project with KT5 can save you thousands in design, time, and unexpected costs.

Q: How Can I Avoid Going Over Budget?

Choose a builder who:

• • Provides a full scope of works

  • Offers fixed pricing

  • Updates costs as the build progresses

Final Thoughts: Ready to Start Building Your Home Extension?

KT5 Construction makes it simple. From the first sketch to the final brick, we manage every detail—saving you time, money, and stress. Our clients choose us for our clear communication, transparent pricing, and commitment to quality.

Book Your Free Consultation Today

💬 Get started on your extension project today with a no-obligation quote.
👉 Contact KT5 Construction