Underestimating works is one of the fastest ways to turn a “good yield” into thin or negative cash flow. A room-by-room budget with contingency is the safer starting point.
Break the job into rooms
Price kitchens (cabinets, worktops, appliances), bathrooms and shower rooms, freshly painted bedrooms with new flooring, utility rooms, hallways and any specialist spaces such as a bar or cinema room separately.
DIY vs trades
Materials-only costing is fine for painting you will do yourself. Keep full trades pricing for plumbing, electrical work and complex fit-outs — and budget certified work where the law requires it.
VAT and contingency
Include VAT where it applies and add a 10–15% contingency for extras that appear once walls are opened. Then feed the grand total back into your deal analyzer.
Try the free renovation cost calculator to sketch a working budget before you instruct contractors.