Designing a House Extension: 5 Things to Consider Before You Start

A house extension is one of the most significant investments you can make in your home. Done well, it can transform how you live, add substantial value to your property, and create spaces you will enjoy for decades. Done poorly, it can create planning headaches, construction problems, and spaces that don’t quite work.

Here are the five things we ask every client to think about before we start design work.

1. What Problem Are You Solving?

The best extensions start with a clear understanding of what isn’t working in your current home. Are you short of kitchen space? Do you need an extra bedroom? Do you want to connect your living space to the garden?

The more specific you can be about the problem, the better the design solution will be. Rather than simply saying “we want a bigger kitchen”, think about how you actually use the kitchen — do you need more worktop space, a larger dining table, a place for children to do homework? This kind of brief produces far better architecture.

“The more specific you can be about the problem, the better the design solution will be. A precise brief produces far better architecture than a vague aspiration.”

2. What is Your Planning Context?

Before investing in design work, it is worth understanding the planning context of your property. Key questions include:

• Is the property listed?
• Is it in a conservation area?
• Have any permitted development rights been removed by planning condition?
• What have neighbouring properties been allowed to build?

A quick check of the planning history of your property on the local council’s website can reveal a lot. We always recommend a pre-design planning assessment before starting sketch designs.

3. What is Your Budget — Really?

Construction costs have risen significantly over recent years. Before committing to a design, it is worth understanding the real numbers:

It is important to be honest about your budget from the outset. A well-designed project that is properly costed from the start is far more likely to be built than one where costs are discovered too late to change course.

4. How Will Construction Affect Your Daily Life?

Construction is disruptive. Depending on the size of the extension and the works involved, you may need to vacate a kitchen for several weeks or live without a functioning bathroom for a period. Think in advance about how you will manage this — whether you will move out temporarily, or adjust your routine.

A well-managed project with a reputable contractor and a clear programme can minimise disruption, but it is never entirely avoidable. A good architect will help you think through the construction sequence at design stage, before work begins.

5. Do You Have the Right Architect?

The quality of the design — and the quality of the working relationship — will have a greater impact on your project than almost any other factor. Look for an architect who:

• Has experience with similar projects in your local area
• Is clear and responsive in their communication
• Can demonstrate good design thinking, not just technical competence
• Provides a clear, transparent fee proposal

“The quality of the working relationship matters as much as the quality of the design. You will spend months working closely with your architect — choose someone you trust.”