This guideline covers recommended procedures for preparing and painting calcareous surfaces such as concrete, masonry, and plaster in construction. It instructs professionals on surface treatment, paint selection, application methods, and defect prevention to achieve long-lasting and attractive finishes suitable for both indoor and outdoor environments.
Overview
This guideline covers recommended procedures for preparing and painting calcareous surfaces such as concrete, masonry, and plaster in construction. It instructs professionals on surface treatment, paint selection, application methods, and defect prevention to achieve long-lasting and attractive finishes suitable for both indoor and outdoor environments.
Audience
Contents
Structure
This section outlines the extent and application of painting operations and workmanship for protective coatings on calcareous surfaces like concrete, masonry, and plaster. It clarifies the terminology used, which is aligned with related Indian Standards, and explains rounding-off rules for test values in compliance with IS 2:1960. Detailed painting schedules are covered in the subsequent part of the standard.
Terminology used throughout is drawn from multiple Indian Standards related to paints and varnishes. The section also emphasizes the importance of rounding numerical test results according to IS 2:1960, ensuring consistency in reporting. Additional painting schedules are referenced from Part 2 of the standard.
Guidance is provided on collecting vital information before painting, including surface type, previous treatments, usage context (interior or exterior), weather exposure, and details of new plasterwork such as backing, undercoats, finishing dates, and lime content. This data supports effective planning and compliance.
This section discusses the properties of calcareous substrates, highlighting their alkalinity and moisture retention. It covers the importance of curing and drying, identification of substrate types, and necessary treatments such as cleaning, biological growth removal, priming, and repair to ensure proper paint adhesion and longevity.
Paint selection is referenced to Part 2, with emphasis on preparing lime plaster surfaces correctly before application. Application methods must adhere to IS 1477 standards. Paint system choice depends on surface conditions and desired finish, with recommendations provided for different substrate types.
Detailed instructions are given for preparing backgrounds, especially lime plaster surfaces, including cleaning, repairing cracks and defects, drying, and priming. Proper preparation ensures optimal adhesion and durability of paint finishes.
This part covers the methods and procedures for applying paint, referencing IS 1477 for tools and techniques. It stresses the importance of proper surface preparation, drying times, number of coats, and environmental conditions for successful paint application.
Recommendations for upkeep and repainting are provided, including inspection, removal of defective coatings, surface cleaning, drying, and repainting according to prescribed methods and schedules referenced in Part 2.
Instructions detail the preparation of lime-based colour washes, including slaking lime, mixing additives, and applying coats with specific brushing techniques. Surface preparation for both new and existing work is also described to ensure uniform and durable finishes.
This section specifies the mixing ratios for cement paints, coverage rates, and preparation of new and old cement or concrete surfaces. It includes recommendations for removing vegetation, repairing cracks, and suitability of primers for gypsum plaster.
Describes tests such as alkalinity assessment and checks for defects like crazing, sweating, and cracks. Guidelines for repair and preparation ensure that plaster surfaces are fit for painting and will support durable finishes.
An enumeration of related Indian Standards referenced for terminology, testing, and application procedures including standards for brushes, paints, testing methods, and concrete specifications.
Details the composition of the Painting, Varnishing and Allied Finishes Sectional Committee responsible for this standard, including representatives from industry, research, government, and academia, ensuring diverse expertise in formulation.
Frequently Asked
Before painting concrete or plaster surfaces, ensure new cement-based surfaces are thoroughly dried and brushed to remove dirt and loose materials. Avoid acid or salt treatments that can worsen efflorescence. For old unpainted surfaces, remove any vegetation with ammoniacal copper solution and brush off dead matter. Repair cracks by cutting them in a V-shape and filling with appropriate mortar, allowing full drying before painting. Previously painted surfaces should be cleaned and repaired similarly. For gypsum plaster, test alkalinity and apply primers if suction is uneven or efflorescence is present. Detailed surface information should be gathered to guide appropriate preparation.
For damp or porous masonry surfaces, paints that permit moisture vapor to pass through are recommended, such as lime wash, colour wash, cement paints, oil-free distempers, and certain emulsion paints. These finishes help prevent moisture entrapment and related defects. Glossy paints should not be applied until the substrate is fully dry. Persistent dampness should be identified and treated before painting. Portland cement paints are ideal for porous, damp concrete or stucco exteriors but are less suitable for frequently cleaned interiors due to erosion concerns.
The standard advises eliminating sources of dampness and ensuring thorough drying of walls to prevent mould. Increasing ventilation helps reduce moisture accumulation. Remove mould-infected paint layers by scraping and brushing, followed by applying two coats of a fungicidal wash such as 2% sodium pentachlorophenate, allowing drying between coats. After 24 hours, dust can be brushed off without washing away the fungicide, and painting can proceed over the treated surface. Equipment used should be cleaned with fungicidal solutions to avoid spreading spores. Persistent mould issues may require repeating treatment.
Tests to assess plaster readiness include an alkalinity test by applying an alkali-sensitive paint and observing for bleaching or saponification after about a week. Surfaces should be free from defective or sticky paint, with any present removed and the plaster allowed to dry completely. Major cracks must be cut in a V-shape and filled appropriately. Moisture levels must be checked and dampness eliminated prior to painting. Only when no alkalinity-related defects are observed, and the surface is dry and sound, should painting proceed.
When repainting lime plaster previously coated, all existing paint, especially if defective, must be completely removed. The plaster should be fully cured and dry before repainting. Hairline cracks require at least two coats of primer compatible with the paint system. Alkali-resistant primers are recommended for solvent-based paints. Use pigments that are lime-fast to ensure durability. Avoid rapid drying to prevent shrinkage cracks, allowing natural carbonation and drying periods when possible. Temporary soft distempers may be used for immediate decoration but should be removed before applying permanent finishes. Moisture content testing is essential before applying solvent-based paints.
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