Why is surface preparation critical for plaster surfaces?

To remove dust, grease, efflorescence, and loose particles, ensuring proper adhesion of the primer and subsequent paint layers.

How should one treat efflorescence prior to painting?

By dry brushing the affected area and leaving the surface for a few days to see if it reappears; avoid washing with water initially.

Can solvent-based paints be applied directly on fresh concrete or plaster?

No, the high alkalinity and moisture of fresh concrete can cause saponification (breaking down of paint). An alkali-resistant primer must be used after the surface is fully dry.

IS 2395

: 2000

Painting of Concrete, Masonry and Plaster Surfaces - Code of Practice, Part 1: Operations and Workmanship

CurrentFrequently UsedCode of PracticeArchitectural · Building Construction Practices incl. Painting, Varnishing

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This code of practice covers the operations and workmanship for painting concrete, masonry, and plaster surfaces. It outlines essential surface preparation steps, methods for handling substrate moisture and alkalinity, and proper procedures for priming and applying paint coats to ensure durable and aesthetically pleasing finishes.

Painting of Concrete, Masonry and Plaster Surfaces - Code of Practice, Part 1: Operations and Workmanship

Quick Reference Values

Substrate curing period before painting28 days (typical minimum)

Drying time between coats for cement paint12 to 24 hours

Safe moisture content of masonry before oil-based paintingBelow 10%

Acceptable pH limit for substrate before painting< 10

Practical Notes

New plaster and concrete must be fully cured and dried (usually 28 days) before painting to prevent blistering, peeling, and saponification.

Efflorescence must be removed completely by dry wire-brushing; do not wash with water initially as it may drive salts back into the substrate.

Ensure cracks are properly widened to a V-groove, cleaned, filled with compatible putty or crack filler, and sanded smooth before applying primer.