Renovation projects exceed budget with such regularity it's practically a law of nature. Ask any architect, contractor or homeowner who has renovated and they'll say the final cost was higher than expected. Some of this is genuinely unavoidable — you can't see inside walls until you open them. But a significant portion comes from failing to account for entirely foreseeable costs.
Start With a Complete Scope
Before any numbers, write a complete scope of work. "Renovate the kitchen" is not a scope. A scope lists every task: strip out units, replace electrical circuits, install new flooring, replaster, install new units, plumb new sink position, redecorate. Only with a complete scope can you estimate accurately. Our area calculator establishes room dimensions underpinning material quantities. Our paint calculator and tile calculator produce accurate material amounts.
Labour Costs — The Bigger Number
Labour typically accounts for 40-60% of total renovation cost. 2025/26 day rates in the UK: builder £250-£400 | electrician £300-£450 | plumber £280-£450 | plasterer £250-£400 | tiler £250-£400. If a quote seems very cheap, ask whether the time estimate is realistic for the scope — it often isn't.
Costs People Forget
- Skip hire: clearing a kitchen or bathroom creates substantial waste. Budget £200-£400 per skip.
- Building regulations approval: structural work and new electrical circuits often need sign-off. Fees £200-£500.
- Party wall agreements: any work affecting a shared wall requires a Party Wall Notice. If a formal agreement is needed: £700-£1,500 per surveyor.
- Temporary accommodation: a full kitchen renovation takes 2-4 weeks. Factor in eating out or staying elsewhere.
- Snagging and making good: the final 5-10% of a project always takes longer than expected.
The Contingency Rule
Add minimum 10% contingency for straightforward work; 20% for projects involving older properties or structural work. Opening walls in pre-1980s UK housing stock reveals unexpected damp, non-compliant wiring, and structural issues far more often than not. A contingency isn't pessimism — it's professional practice.
Get Three Quotes Minimum
A wide spread in quotes (£8k, £14k, £18k for the same job) signals different scopes being priced. Go back to outliers with specific questions before assuming the cheapest is the best deal — cheap quotes that grow mid-project are far more expensive than honest ones that don't.
Further reading: The HomeOwners Alliance provides independent renovation guidance and contractor vetting advice. Visit HomeOwners Alliance for renovation guidance.