7 Hidden Renovation Costs That Catch UK Homeowners Off Guard
You’ve got a plan, a quote, and a Pinterest board that deserves its own gallery. But somewhere between strip-out and sign-off, renovation costs can swell. Not from splurges – but from surprises.
Across hundreds of projects, we’ve seen the same patterns play out: unexpected repairs, underestimated red tape, and the quiet expenses that add up when no one’s looking. Whether you’re planning a new kitchen or full home refit, here are seven of the most common hidden costs – and how to prepare for them.
TL;DR
Even well-planned UK renovations come with surprises. Expect hidden costs in surveys, structural repairs, rewiring, material price hikes, insurance, finishing work, and post-build upgrades. Plan properly, add 10–15% buffer, and ask questions early – it’s the best way to avoid costly detours.
1. Planning, Surveys and Permissions
Before building begins, paperwork takes centre stage.
On average, applying for planning permission in the UK costs between £250 and £650 depending on the scope of the project. For a single-storey extension, expect to pay around £258, according to the UK Planning Portal. But permissions often come with extras – like building control applications, structural surveys, and drainage inspections – which can add another £400 to £800 upfront.
Even minor renovations might trigger costs for lawful development certificates or party wall notices. They're easy to overlook, but essential to avoid delays or legal headaches later on.
2. Structural Issues: Damp, Rot and Movement
Once demolition starts, hidden problems can surface fast – and they’re rarely cheap to fix.
Damp proofing: On average, between £5,000 and £16,000 depending on the scale of the issue
Subsidence repair: Typically costs £5,000 to £8,000
Rot treatment: Between £1,000 and £2,000
Woodworm: Usually £400 to £800
These aren’t upgrade costs. They’re safety and compliance essentials. According to the HomeOwners Alliance, these structural setbacks are among the top reasons UK renovations exceed budget.
3. Electrical and Plumbing Upgrades
Older homes don’t always support modern living.
If your system can’t handle new layouts or power demands, you may need a full rewire – which typically costs between £4,500 and £7,000. Plumbing changes, especially when relocating bathrooms or kitchens, can cost £1,000 to £3,000, particularly if walls or floors need lifting.
These aren’t always part of the initial quote. At Beams, we recommend early inspections so electrical and plumbing demands are priced in during the planning stage – not mid-way through build.
4. Material and Labour Price Increases
Prices don’t just rise year to year – they rise during projects.
Since 2021, material costs have climbed significantly. According to Checkatrade, items like bricks, timber and insulation increased by over 20% across 2021–2023. If you’ve planned your budget months in advance, these rises can eat into contingency.
Skilled labour is also under pressure. In high-demand areas like London, short delays can lead to higher costs if workers need rescheduling or site conditions change. For larger projects, we advise clients to set aside at least 10–15% of their budget for shifting labour or material prices.
5. Insurance, Storage and Temporary Accommodation
A renovation zone isn’t always livable – and when it's not, the hidden costs begin to stack up.
Short-term rent during construction: £500 to £1,200 per week in London
Storage for furniture or fittings: £30 to £70 per week
Temporary increases in insurance premiums due to building works
If you're carrying out major works – rewiring, structural repairs, or damp treatment – you may need to leave the property temporarily. These costs are easy to forget during early planning and often go unquoted.
We always inform clients to contact their insurer before starting work to ensure their policy remains valid and offers the right level of protection.
6. Making Good: Restoring What Wasn't Quoted
After trades complete their tasks, you’re often left with the “in-between” – and it’s not always included in their scope.
Making good typically involves replastering, repainting, patching ceilings and flooring. On average:
Replastering a single room: £300 to £800
Full house redecorating: £2,000 to £6,000
This is also the point where finish choices – like bespoke cabinetry, complex tiling, or upgraded lighting – can add significant labour hours. If you're planning a bathroom upgrade, for example, material choices (like tiled vs acrylic shower enclosures) can shift the quote by thousands.
7. Fixtures, Fittings and Finish-Upgrades
This is the budget killer that sneaks in quietly.
You start with standard finishes, then upgrade to brushed brass, underfloor heating, smart switches, and a handmade splashback. None of these are essential – but once the main work is done, they suddenly feel like must-haves.
According to Pad Magazine, UK homeowners spend an average of £562.10 on unexpected repairs, and 11% spent more than £1,000. That doesn’t even touch finishing flourishes – which often double that figure.
We recommend setting aside an additional 5–10% for finish upgrades alone. It gives you breathing room for choice without risking overspend.
Beams Renovation’s View
At Beams, we believe renovation should be transformative – not traumatic. Unexpected costs are part of the process, but they shouldn't derail the outcome.
That’s why we begin every project with laser scans, data-backed pricing, and a clear scope. It helps us surface risks early and keep surprises minimal.
We’ve delivered hundreds of projects across London – from compact flat refurbishments to full home renovations – and in our experience, the homeowners who stay on budget are the ones who:
Set aside contingency
Ask detailed questions about what's included
Understand that “nice to have” can wait
Invest in early inspections, not just end finishes
Most surprises in renovation aren’t random – they’re the result of unseen conditions or unclear planning. With the right prep, you can anticipate them and move forward with confidence.
FAQs About Hidden Renovation Costs in the UK
How much contingency should I set aside for my renovation?
We recommend setting aside 10–15% of your total budget to cover hidden costs like structural repairs, planning fees, and finishing work. For a clearer picture of what your project might cost – including a built-in contingency – see our UK renovation cost guide and calculator.
Are structural repairs like damp proofing included in most renovation quotes?
Not usually. Issues like damp, rot, or subsidence are often only discovered after strip-out begins, so they’re rarely in the initial quote. That’s why early inspections are key. If you’re considering major works, it’s worth reading our advice on different types of contractors so you know who can manage these repairs.
How do material price rises affect my project?
Material and labour costs can increase mid-project – especially in high-demand areas like London. If your design involves premium finishes like bespoke worktops or high-end appliances, even small price changes can add up. Our comparison of gas vs induction hobs explains how energy and supply trends can influence your final bill.
Do I need extra insurance during a renovation?
Yes – most insurers require you to inform them before major works begin, and your premium may rise temporarily. If your renovation involves plumbing or bathroom upgrades, you may also want to check whether your fixtures are covered. Our bath vs walk-in shower comparison covers long-term value and practical considerations.
What’s the biggest hidden cost homeowners overlook?
“Making good” – replastering, painting, and restoring floors – is one of the most underestimated costs. It’s the stage between trades finishing and your home feeling complete. For kitchens, even small finishing changes like upgrading from standard fittings to premium fixtures can make a big difference. See our undermount vs Belfast sink guide for an example of how these decisions can affect budget and style.
Is it better to plan a renovation all at once or in stages?
It depends on your budget and tolerance for disruption. Full refits can be more cost-effective overall, but staged renovations spread costs over time. Our article on 10 reasons to renovate outlines the pros and cons of both approaches.
Can lighting choices impact my renovation budget?
Absolutely. Bespoke lighting can add thousands to a project, especially if it requires rewiring. Even simple changes – like switching from standard pendants to recessed spotlights – can increase labour time. For design inspiration, see our guide to kitchen ceiling lights.