PLAIN-ENGLISH PROJECT GUIDES
Is my budget actually realistic?
Separate the building work from the other costs, then test what happens if the scope or assumptions change.
Start with the whole project
A builder’s price and your total budget are not the same thing. Start with the work itself, then list professional input, surveys, approvals, utilities, external works, finishes you will buy directly and any temporary accommodation. Show tax assumptions clearly and ask the right adviser to confirm them.
Keep unknowns visible
A contingency is money held for uncertainty, not a second pot for upgrades. An older building with limited survey information needs a different risk discussion from a well-defined new-build package. Do not choose a percentage simply because someone else used it. List the actual unknowns and who will investigate them.
Try a smaller version
Put each requirement into essential, desirable or optional. Price a baseline that achieves the main purpose, then show additions separately. For example, retaining a workable kitchen location may reduce alterations, but that needs checking against the actual layout and services.
Know when to refresh the numbers
Update the cost plan after surveys, design changes and tender returns. Record the date and assumptions so an early allowance is not mistaken for a current contractor offer. Our calculator is a starting range, not a fixed price.
Your practical checklist
- Write down your total spending limit, not only the building allowance.
- List the items outside the builder’s scope.
- Record unknowns and a decision date for each.
- Test a simpler option before reducing contingency.
Useful independent guidance
RICS: home extensions and improvements · Planning Portal: finance and budget
General guidance, not a quotation or project-specific legal, design, valuation or financial advice. Services and professional responsibilities are agreed separately.