Planning a home extension is exciting – the thought of a bigger kitchen, a light-filled dining space, or even a new bedroom can be transformative. But many homeowners worry about one thing above all: overspending.
The truth is, extensions don’t need to spiral out of control. With the right planning, expert guidance, and smart decision-making, you can create the home you want without blowing your budget. At Reltic Extend, we’ve helped families across London and Surrey manage their extension costs wisely – here’s how you can do the same.
Why Overspending Happens
Overspending usually isn’t about one big mistake – it’s the small things that add up. Common causes include:
Changing designs after construction starts,
Underestimating costs during planning,
Choosing builders who don’t provide detailed contracts,
Forgetting about planning fees, building regulations, or VAT,
Opting for high-end finishes without balancing priorities.
💡 Want to set realistic expectations? Try our free Cost Calculator before you start.
Step 1: Start With a Clear Budget
Before you even begin design, decide:
How much you want to spend,
What’s essential vs. what’s optional,
How much contingency you’ll allow (10–15% is typical).
This clarity avoids costly surprises later. Our How We Work approach ensures budgets are agreed upfront and carefully managed.
Step 2: Choose the Right Extension Type
Some extensions naturally cost more than others. Picking the right type for your needs avoids overspending on unnecessary space.
Rear Extensions – cost-effective for larger kitchens and dining areas.
Side Extensions – great for narrow homes but usually smaller in scale.
Kitchen Extensions – focus on the most valuable space in the house.
Wraparound Extensions – bigger investment, but transformational.
Double Storey Extensions – higher upfront cost, but more value per square metre.
Step 3: Factor in Planning & Permissions
Planning applications, structural reports, and building regulations all have associated costs. Failing to include these in your budget can throw things off track.
Visit our Planning page to learn more about fees and permissions in London and Surrey.
Step 4: Avoid Design Changes Mid-Project
One of the fastest ways to overspend is changing your mind once work begins. Moving walls, altering layouts, or upgrading finishes after construction has started can add thousands to your bill.
Our Design Build Process ensures all details are agreed before the first brick is laid.
Step 5: Balance Quality With Cost
It’s tempting to go for the most luxurious finishes everywhere, but smart budgeting means knowing where to spend and where to save.
Invest in structural quality, insulation, and glazing – they add long-term value.
Save on decorative finishes that can easily be updated later.
Choose timeless designs that won’t need frequent changes.
Step 6: Compare Regional Cost Factors
Costs vary depending on location. For example:
North London – often higher due to period home requirements.
South London – competitive pricing for wraparounds and family kitchens.
East London – compact builds mean smaller budgets.
West London – premium projects with high-end finishes cost more.
Surrey – larger plots allow for bigger builds and budgets.
Step 7: Use a Transparent Payment Structure
Avoid overspending by agreeing clear staged payments tied to progress, not vague timelines. A typical structure might include:
Deposit,
Payment after foundations,
Payment after structure completion,
Final payment after handover.
At Reltic Extend, we keep payments structured and transparent so you’re always in control.
Mistakes to Avoid
Choosing builders based on lowest quotes without checking what’s included.
Forgetting VAT – a common oversight that inflates costs.
Not budgeting for landscaping after the extension is complete.
Relying on rough estimates rather than detailed breakdowns.
Our Warranty and Insurance gives you confidence that your money is well protected.
Final Thoughts
Overspending on an extension isn’t inevitable. With the right planning, a clear budget, and professional guidance, you can keep costs under control and still achieve the home you’ve always wanted.
At Reltic Extend, we combine design, planning, and construction into one seamless service – giving you clarity and cost confidence at every step.
Why choose Reltic Extend?
By offering a complete service, we give you:
peace of mind – everything handled by one trusted team,
control – clear budgets and timelines,
value – a home extension designed to increase your property’s worth,
support – guidance at every step, from planning to handover.
Meet the people who make it happen on our Who We Are page.
Ready for a complete extension service?
Don’t waste time managing multiple contractors. With Reltic Extend, you get everything under one roof – from design through to handover.
👉 Contact us today via our Contact page. Let’s plan your dream extension and deliver it with clarity, quality, and care.
