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.
