Work out how much of a roof or façade contract to hold back as retention until the defects period ends, and what is still due after the advance you paid.
Use this calculator at the completion stage of a roofing, waterproofing, cladding or painting job, when the contractor asks for the final bill. Enter the total contract value as agreed in writing (including GST if GST is charged), the retention percentage the contract allows you to hold back, any deductions agreed for items not done or done badly, and the advance and stage payments you have already made.
Formula: amount held back = contract value × retention % + agreed deductions. Payable at completion = contract value − amount held back − payments already made.
Worked example (illustrative): a ₹2,00,000 waterproofing contract plus 18% GST is ₹2,36,000. You paid a 30% advance (₹70,800) and 30% after the base coat (₹70,800), so ₹1,41,600 is already paid. With 10% retention (₹23,600) held until one monsoon has passed without leaks, the amount payable at completion is 2,36,000 − 23,600 − 1,41,600 = ₹70,800.
Limits: retention only works if it is written into the contract with the release condition (for example, a dated inspection after the first monsoon). The percentages here are examples, not a legal standard. See the contract and warranty checklist.
Estimates, Worked Examples and Checklists
Worked example of measuring and pricing exterior repainting for an apartment building in India and splitting the cost per flat by area or equally, with GST and retention.
Failures, Claims and Official Sources
How a household can complain about a failed roof, waterproofing, cladding or paint job in India: notice, National Consumer Helpline, e-Jagriti filing, limits, fees and timelines.
Costs, Systems and 2026 Rules
Who decides and who pays for terrace waterproofing, external painting and façade changes in Indian housing societies and apartment associations, and how to get approval.
