10 Questions to Ask Before Planning Your Extension in Surrey

Before you start sketching out dream layouts or calling in the builders, there’s a bit of quiet thinking that needs to happen first. The best home extensions don’t just look great, they work brilliantly for the people living in them. And in a place like Surrey, where homes come in all shapes and planning rules can be a little nuanced, it pays to get clear on your goals from the very beginning.

If you're sketching and planning without outside help then here are ten questions I encourage every homeowner to ask themselves before diving into the design stage. They’ll help you plan with more purpose, avoid common mistakes, and create something that truly supports the way you want to live.

1. What problem am I trying to solve?

It sounds simple, but it's easy to lose sight of this when you’re caught up in Pinterest boards and kitchen envy. Are you desperate for more space to gather as a family? Is it about creating a home office, improving flow, or bringing in more light? Start here, because the clearest briefs lead to the most successful outcomes.

2. How long do I plan to stay in this home?

If this is your forever home, you might want to future-proof it. Think accessible layouts, multi-purpose rooms, and quality finishes. If it’s more of a five-year plan, your priorities (and budget) might be different, focusing on adding value or making it more sellable.

3. What’s my realistic budget, including the “invisible” costs?

Be honest with yourself about what you can afford, and don’t forget costs like VAT, planning fees, structural engineers, party wall surveyors, and professional design support. Leaving a contingency (10 - 15% is wise) can also give you breathing room when the unexpected inevitably pops up.

4. Do I know what kind of extension I’m allowed to build?

Surrey’s planning rules can vary from borough to borough and they get even more specific in conservation areas or with listed buildings. Before you fall in love with a design, check whether permitted development applies, or if you’ll need full planning permission.

5. How will the new space connect with the existing house?

A great extension shouldn’t feel like a bolt-on. Think about how the new room will flow from the rest of the house. Will it change how you use the existing rooms? Could a small internal tweak make the whole layout work better?

6. Will the extension affect the light in other rooms?

Bigger doesn’t always mean brighter. A deep rear extension, for example, can unintentionally block natural light from reaching the centre of the house. Consider roof lights, internal glazing, or lighter finishes to keep things feeling airy throughout.

7. Do I need planning permission, a lawful development certificate, or both?

This one often catches people out. Even if your extension falls under permitted development, getting a lawful development certificate is a smart move. It gives you proof the build was legal (especially useful if you sell later). And if you do need full planning? Start early and allow time for it.

8. Have I thought about the neighbours?

Whether or not they can object officially, it’s always worth having an early, friendly conversation if your project might affect them, especially if you're building near a boundary. It can help avoid disputes, delays, and tension when the scaffolding goes up.

9. Will I stay in the house during the build, and is that realistic?

Living through a renovation can be done, but it’s not for everyone. Think about your schedule, your tolerance for dust and disruption, and whether you’ll have a working kitchen or bathroom throughout. Some families opt to move out for the trickiest phases — even if just temporarily.

10. How do I want the space to feel, not just look?

This is the question people often skip but it’s one of the most important. Is it calm? Sociable? Cosy? Light-filled? Your answers should shape everything from layout to materials. A successful home extension doesn’t just function well, it should feel right every time you walk in.

Starting with these questions will help you make smarter decisions, feel more in control of the process, and ultimately create a space that genuinely enhances your life.