Pre-Monsoon Repainting of a Chalky, Damp Hostel Facade
A 12-year-old hostel near Puri needs its exterior repainted before the monsoon, about six weeks away. The paintable area is roughly 900 m² of cement plaster that was last coated with cement paint and is now chalky and powdering. A moisture meter gives 18–22% on the north wall after three dry days at 32 °C and 85% relative humidity; there are damp patches and efflorescence near the plinth, and about 3 m² of plaster sounds hollow. The contractor's offer reads: wire-brush the surface, one coat of primer 'as required', two coats of exterior emulsion, four days drying between coats, lump sum ₹1,10,000, no warranty beyond the monsoon. A branded material schedule has been omitted.
1. Give the reasons, in order of seriousness, why this specification is likely to fail within one monsoon, and state the evidence you would record on site.
Read the worked answer
- The substrate is wet. At 18–22% moisture, an emulsion film cannot bond and cannot breathe outward; water vapour will lift it as blisters and sheets, usually within weeks of the first heavy rain. Any coating over damp plaster is money thrown away. Evidence: moisture meter readings at ten marked grid points on the north wall, dated, with a photograph of each reading.
- Chalky cement paint is the worst possible base. Cement paint is highly alkaline and powdery. Emulsion applied over it will not adhere; it will peel in sheets. It must be removed by scraping and wire brushing, or the surface stabilised with an alkali-resisting primer compatible with the new system.
- The 3 m² of hollow plaster is unaddressed. Hollow, drummy plaster will detach and take the paint with it. Evidence: hammer-tap survey marked on an elevation sketch.
- The efflorescence has not been cured, only covered. Salt at the plinth means water is rising or a downpipe is discharging there; the source must be fixed before decorating.
- Practical drying windows are ignored. Four days between coats is not the problem - the problem is applying at 85% RH with rain imminent. Exterior emulsion needs a dry surface and a falling moisture forecast; recoating is typically within the manufacturer's window (often 4–6 hours at 32 °C), not four days.
- No material schedule and no warranty means no lever if the product is substituted with a cheap grade.
2. Rewrite the specification: surface preparation, priming, filling, coating schedule, and a programme that fits the six-week window for 900 m².
Read the worked answer
Preparation: fix the water source first - re-route any downpipe, repair plinth protection, and allow the wall to dry. Scrape and wire-brush off all chalky cement paint, wash with clean water, then treat with a fungicidal wash where algae exist. Cut out and re-plaster the 3 m² hollow area in 1:4 cement mortar with a bonding agent, and cure it 7 days. Dry-brush the efflorescence away; do not wash salts back in.
Acceptance gate: do not proceed until the moisture meter reads 12% or less at every grid point on two consecutive dry days. This is the single decision that determines success.
System: one coat of alkali-resisting exterior primer, thinned as directed; exterior-grade cementitious or acrylic putty to fill pores and hairline cracks, sanded; then two coats of exterior acrylic emulsion, each at the manufacturer's wet film build to give roughly 50–60 microns total dry film thickness. Follow the manufacturer's recoat interval.
Programme for 900 m² in six weeks: days 1–2 organise access and scaffolding; days 1–8 preparation and patching, with 7 days curing for the patch overlapping the work front; days 9–10 moisture gate and primer; days 11–16 first coat; days 17–20 second coat, working the elevation in 100 m² sections so walls are never left half-coated into rain. With four painters at 25 m² per day, each coat takes about nine working days - plan for 22 working days and keep eight days as weather buffer. Never paint a wall that will be rain-washed within 24 hours.
3. How would you measure and certify the work for payment, and what would you refuse to pay for?
Read the worked answer
Measurement rules: measure painting in square metres of finished surface, item by item, with primer, putty and each coat priced separately rather than hidden in a lump sum. Deduct openings exceeding 0.5 m² (doors and windows); add separately for jambs, reveals, soffits and mouldings where actually painted. Measure only the area that received the specified number of coats at the specified film thickness, and record joint measurements signed by both parties on the day.
Quality evidence: dry film thickness readings on a marked grid (for example one reading per 100 m², averaged, with a minimum), a pull-off or cross-cut adhesion check on each elevation, and dated photographs of preparation before primer. Retain the sealed material tins and batch numbers.
Payment I would refuse or withhold: any area painted on a substrate reading above 12% moisture; any coat applied over chalky or drummy plaster; areas where the specified number of coats or the film thickness is not achieved; all work done during rain or with rain forecast within the drying window; and any substituted material without written approval. Retain 5–10% of the value until one monsoon has passed, backed by a written warranty covering peeling, blistering and efflorescence recurrence - that clause, not the price, is what protects the client.