Money
What a contingency is actually for
It is not a discount fund, and it is not spare money for a better kitchen. It is the only part of your budget that buys you the right to say no.
July 2026 · 7 min read · The Construction Clinic
Almost every homeowner sets a contingency. Almost every homeowner spends it in the first third of the project, on things that were not surprises.
The pattern is consistent: the contingency is treated as the last slice of the budget rather than as insurance against the unknown, so it is used to upgrade rather than to absorb. By the time the genuine unknown arrives — and it usually arrives underground — the buffer is gone and the only remaining options are borrowing, cutting quality, or stopping.
“Contingency spent on choice is contingency unavailable for necessity. The difference shows up in month four.”
How much, honestly
For new-build or straightforward extension work on a well-understood site, ten per cent of the construction cost is a defensible starting point. For work to an older property, anything involving existing foundations, or a project where the structural design is not complete at the point of pricing, fifteen to twenty per cent is closer to reality.
That percentage sits on top of the construction cost, alongside fees, statutory charges, insurance and the cost of living elsewhere if you have to move out. Contingency is not a line in the builder's quote. It is a line in yours.
Rules that keep a contingency alive
- Nothing discretionary is released until the structure is complete
- Every release is written down with a reason
- Upgrades come from the main budget or they do not happen
- Review the remaining balance at every site meeting
The strategic value of an untouched buffer
There is a behavioural effect that has nothing to do with arithmetic. Homeowners with an intact contingency negotiate differently. They can absorb a genuine additional cost without panic, which means they can also refuse an unnecessary one without fear.
Homeowners who have spent it early lose that position. Every subsequent conversation is conducted from a place of shortage, and shortage tends to produce the two worst outcomes in construction: rushed substitution and deferred work.
The last word
Write down what your contingency is, where it is held and what it may be spent on, and share those three lines with whoever else is making decisions with you.
Then leave it alone until the structure is up and the ground has told you the truth.