Extending your home is exciting – it’s a chance to add space, improve your lifestyle, and boost property value. But with excitement often comes a little anxiety: how do you keep the project on budget without sacrificing comfort or design quality?
At Reltic Extend, we work with homeowners across London and Surrey who want to unlock more space in their homes while staying financially secure. In this guide, we’ll share practical advice on keeping your extension affordable, comfortable, and future-proof.
Why Sticking to a Budget Matters
When it comes to home extensions, overspending is a common pitfall. Without proper planning, costs can creep up through:
design changes halfway through,
hidden structural challenges,
underestimated finishes and fixtures,
planning or regulatory fees you didn’t account for.
By managing your budget wisely, you’ll enjoy:
Peace of mind – no last-minute financial stress,
Smart investment – money spent where it really adds value,
Confidence in decisions – clarity around priorities and upgrades,
Better property value – an extension that pays off in the long run.
💡 To get started, try our free Cost Calculator for an instant estimate tailored to your project.
Step 1: Plan Early, Plan Smart
Budget success begins with clear planning. Homeowners who prepare early avoid last-minute surprises and enjoy a smoother journey. Here’s how to start:
Define your must-haves – for example, a kitchen island, skylights, or bi-fold doors.
List the nice-to-haves – luxury finishes or statement lighting.
Set a realistic budget – always add at least 10% contingency for the unexpected.
At Reltic Extend, we guide you through the whole process. You’ll see exactly how we do it in our How We Work and Design Build Process guides.
Step 2: Choose the Right Extension Type
The type of extension you choose makes a big difference to your budget.
Rear Extension – often the most cost-effective way to expand, perfect for creating open-plan kitchen diners.
Side Extension – ideal for terraced homes, maximises narrow plots.
Wraparound Extension – more complex and costly but creates dramatic space.
Double Storey Extensions – higher initial cost but delivers great value per square metre.
Kitchen Extension – a lifestyle investment that can become the heart of the home.
Choosing the right type helps you stay within budget while maximising space.
Step 3: Materials – Spend Smart, Not Excessively
It’s tempting to overspend on finishes, but balance is key. Here’s how:
Prioritise structure – strong foundations, insulation, and roofing always come first.
Mix finishes – choose mid-range flooring or countertops while investing in high-quality windows and doors.
Think long-term – energy-efficient glazing and insulation reduce bills for years to come.
If you want to see how quality and cost balance together, explore our Warranty and Insurance section – peace of mind built into every project.
Step 4: Don’t Forget Planning & Permissions
Unexpected planning issues are one of the biggest budget breakers. Early preparation prevents costly delays.
Our Planning page explains everything you need to know about:
when planning permission is required,
permitted development rights,
working with neighbours,
listed building considerations.
By planning ahead, you save time and money – and keep your project on schedule.
Step 5: Location Matters – Costs Across London & Surrey
Extension costs vary depending on where you live. For example:
North London – property styles often suit side returns and rear extensions.
South London – wraparounds and open-plan kitchens are popular.
East London – modern designs fit well with compact homes.
West London – premium finishes and double-storey extensions are in demand.
Surrey – larger plots mean bigger opportunities for kitchen and wraparound projects.
Knowing regional trends helps you benchmark your budget against similar projects.
Step 6: Avoid the Most Common Budget Mistakes
Many homeowners end up spending more than expected because of:
Changing the design after construction begins,
Forgetting about VAT,
Choosing luxury finishes everywhere,
Ignoring drainage or groundworks costs.
At Reltic Extend, we make sure you’re fully informed at every step – no surprises, no hidden extras.
Step 7: Work With the Right Team
Your budget is only as secure as the professionals behind it. With Reltic Extend, you get:
Accurate estimates upfront with our Cost Calculator,
Transparent payment structures,
A full-service team – from planning to construction,
Trusted guidance from experts who care about your home.
Learn more about us in our Who We Are page.
Final Thoughts
Keeping your extension on budget doesn’t mean compromising on comfort, style, or value. With smart planning, the right extension type, and a trusted partner, you can achieve the home you’ve always dreamed of – without overspending.
Ready for a complete extension service?
Ready to plan your extension with confidence?
👉 Start today with our free Cost Calculator and discover what’s possible for your home.
Or contact us directly to discuss your project in detail. With Reltic Extend, you get a complete service – from design through to handover.
