Plastering Works SOP

Standard Operating Procedure for internal and external plastering works ensuring durability, aesthetic finish, and quality workmanship as per IS 1661:1972 specifications.

Duration: 7-14 days Team: 4-6 workers Risk Level: Medium

1. Purpose

To establish a standardized procedure for plastering works ensuring smooth, durable, and aesthetically pleasing wall finishes while maintaining quality standards and structural integrity for both internal and external surfaces in accordance with project specifications.

2. Scope

This procedure applies to all internal and external plastering activities including surface preparation, mixing, application, finishing, and curing for walls, ceilings, columns, and other areas requiring plaster treatment in residential, commercial, and industrial construction projects.

3. Responsibilities

Site Engineer

Oversees quality compliance & specifications

Mason Supervisor

Leads plastering team & ensures proper execution

Safety Officer

Ensures PPE usage and safety protocol adherence

Masons & Helpers

Execute plastering work & material handling

Quality Inspector

Conducts inspections & rectifies defects

Material Manager

Ensures timely availability of required materials

4. Materials & Tools

Cement

OPC 43/53 Grade or PPC as specified

Sand

Well-graded, silt-free sand (FM 2.0-3.0)

Water

Clean potable water free from impurities

Admixtures

Waterproofing compounds, plasticizers

Measurement Tools

Plumb bob, spirit level, straight edge, measuring tape

Plastering Tools

Trowels, floats, hawks, screeds, brushes

Mixing Equipment

Mechanical mixer, pans, buckets, gauge boxes

Scaffolding

Secure platforms for height work

5. Procedure

1
Surface Preparation
  • Clean the surface thoroughly to remove dust, oil, paint, and loose particles
  • Rake out joints in masonry to 10-15mm depth to provide mechanical key
  • Roughen smooth concrete surfaces using wire brushes or hacking tools
  • Ensure all electrical conduits and plumbing pipes are properly embedded
  • Fix chicken mesh at junctions of dissimilar materials (e.g., concrete-brick)
  • Install corner beads at external corners for better finish and protection
  • Fix aluminum/steel strips for expansion joints at specified locations
  • Wet the surface thoroughly for at least 24 hours before plastering
  • Apply cement slurry as bonding agent on smooth surfaces (1:1 cement:water)
  • Ensure surface is damp but not dripping wet at time of application
  • Mark level dots or strips at intervals to maintain uniform thickness
  • Verify plumb of wall/surface before starting plastering work
2
Mortar Preparation
  • Use specified mortar mix ratios as per project requirements:
  • Internal plastering: 1:4-1:6 (cement:sand) ratio
  • External plastering: 1:3-1:4 (cement:sand) ratio
  • Ceiling plastering: 1:3 (cement:sand) ratio
  • Use mechanical mixer for consistent quality and thorough mixing
  • Measure materials by volume using gauge boxes, not by shovel
  • Ensure sand is sieved through 4.75mm sieve to remove coarse particles
  • Mix dry ingredients thoroughly until uniform color is achieved
  • Add clean water gradually to achieve workable consistency
  • Continue mixing for at least 3 minutes to ensure homogeneity
  • Add waterproofing compounds for external plaster as per manufacturer's specs
  • Prepare mortar in batches that can be used within 30 minutes
  • DO NOT retemper hardened mortar by adding water
  • Test mortar consistency with trowel (should form cone without slumping)
  • For waterproof mortar, add waterproofing admixture at 2% of cement weight
  • For improved workability, add plasticizer as per manufacturer's recommendations
  • Ensure water-cement ratio is between 0.4-0.6 for optimal strength
3
Establishing Guidelines
  • Create plaster screeds (dots and strips) at 2m intervals on wall surface
  • Apply mortar dots and allow to set partially (1-2 hours)
  • Verify plumb and alignment of dots using plumb bob and spirit level
  • Connect dots with vertical strips of mortar (known as "screeds")
  • Create horizontal screeds at top and bottom of the wall
  • Ensure uniform thickness of plaster through screeds (10-15mm)
  • Allow screeds to set for sufficient time (minimum 24 hours)
  • Maintain consistent thickness throughout the plastering area
  • Mark locations for any special features (grooves, projections, etc.)
4
Plaster Application
  • Apply plaster in the following sequence:
  • Ceiling first, then walls from top to bottom
  • For multi-coat application:
  • Base/Scratch Coat: 8-10mm thick, roughened surface
  • Second/Brown Coat: 6-8mm thick (if required)
  • Final/Finishing Coat: 3-4mm thick for smooth finish
  • Apply mortar by throwing forcefully onto the surface, not by troweling
  • Press mortar firmly against the surface to ensure good adhesion
  • Fill spaces between screeds in sections working from top to bottom
  • Level the applied plaster using a straight edge resting on screeds
  • Remove excess mortar and fill depressions (repeated until uniform)
  • Allow base coat to partially set before scratching for key
  • Cure the base coat for 2-3 days before applying the finish coat
  • Ensure surface is dampened before applying subsequent coats
  • For single coat application, ensure minimum 12mm thickness
5
Finishing Techniques
  • Allow plaster to set partially until thumbprint hard
  • Apply appropriate finishing technique based on requirements:
  • Smooth Finish: Use steel trowel in circular motion
  • Sand Faced Finish: Use wooden float with circular motion
  • Rough Cast Finish: Throw small pebbles onto wet plaster
  • Pebble Dash: Apply pebbles over a wet mortar backing
  • For smooth finish, sprinkle water lightly during troweling
  • Work in small sections to ensure consistent finish
  • Create decorative features (grooves, patterns) while plaster is workable
  • For exposed corners, ensure neat and clean edges
  • Check surface continuously with straight edge for evenness
  • Avoid overworking the plaster as it can weaken the surface
  • Clean edges at junctions with floors, ceilings, and openings
6
Curing & Protection
  • Allow plastered surface to set for 24 hours
  • Start curing by lightly spraying water after initial setting
  • Keep plastered surfaces continuously moist for curing period:
  • Internal Plaster: Minimum 7 days
  • External Plaster: Minimum 14 days
  • Apply water using a fine mist spray to avoid damage
  • Use wet gunny bags or burlap for vertical surfaces
  • Cover with plastic sheets in hot or windy conditions
  • Protect newly plastered surfaces from rain, direct sun, and wind
  • Prevent mechanical damage during curing period
  • Ensure no load is placed on plastered surfaces for 7 days
  • Monitor for early development of cracks and repair immediately
  • Document curing schedule as part of quality records

6. Quality Control

Thickness Check

Verify total thickness is within ±2mm of specification (Internal: 12-15mm, External: 18-20mm)

Surface Evenness

Max 3mm deviation when checked with 2m straight edge in any direction

Plumb & Alignment

Maximum 3mm deviation per meter height; 8mm max for full height

Crack Inspection

No visible cracks greater than 0.5mm width permitted

Surface Texture

Consistent finish as per specifications; no trowel marks or blemishes

Hollow Detection

Test by tapping with wooden mallet; no hollow sounds indicating poor adhesion

Corner Finish

Perfect right angles at internal corners; rounded as specified for external corners

Moisture Resistance

Water test for external plaster after 21 days; no water penetration

7. Safety Measures

PPE Usage

Helmets, gloves, goggles, dust masks, safety boots, and reflective vests mandatory

Scaffold Safety

Inspect daily, stable base, proper guardrails, access ladder, maximum load limits observed

Manual Handling

Proper lifting techniques, team lifting for loads >25kg, use mechanical aids when possible

Housekeeping

Clean work area, clear access paths, proper waste disposal, organized material storage

Electrical Safety

Waterproof connections, GFCI/ELCB protection, regular inspection of cords and equipment

Weather Precautions

No work during storm warnings, lightning, heavy rain, or strong winds (>25 km/h)

Chemical Safety

SDS for all materials, emergency eyewash station, calcium chloride/admixture handling protocols

First Aid

First aid kit readily accessible, trained first aider on site, emergency contact information displayed

8. Documentation & Compliance

Material test certificates for cement, sand, and admixtures
Daily progress reports with locations and quantities completed
Quality control checklists for each area completed
Photographic evidence at key stages (before, during, after)
Curing schedule records with dates and methods
Non-conformance reports and rectification details if applicable
Sign-off forms for completed work by QC and client representative

9. Troubleshooting & Common Issues

Cracks in Plaster
  • Causes: Excess water in mix, poor curing, rapid drying, structural movement
  • Solutions: Maintain proper water-cement ratio, ensure thorough curing, use fiber-reinforced plaster, provide control joints at appropriate intervals
Debonding & Hollow Spots
  • Causes: Inadequate surface preparation, dusty substrate, insufficient curing, application over dry surface
  • Solutions: Remove and reapply with proper surface preparation, ensure substrate is clean and pre-wetted, apply bonding agent where necessary
Efflorescence (White Deposits)
  • Causes: Soluble salts in materials or substrate, water penetration, poor DPC
  • Solutions: Use salt-free materials, incorporate waterproofing compounds, ensure proper damp-proof course, brush off deposits with dry brush and apply diluted acid solution (1:10 acid:water)
Uneven Surface
  • Causes: Improper screeding, inconsistent application technique, poor workmanship
  • Solutions: Use proper screeding techniques, check with straight edge frequently during application, apply additional thin finishing coat after proper preparation

10. Environmental Considerations

Water Management

Minimize water wastage during curing and cleaning, collect and reuse where possible

Waste Reduction

Reuse leftover mortar for non-critical applications, proper segregation of waste

Dust Control

Water spraying during mixing, dust barriers around work area, covered material storage

Weather Considerations

Avoid extreme temperatures (<5°C or >40°C), protect from rain, adjust curing methods by season

11. Pro Tips

Workmanship

Work in smaller sections for better control; avoid overworking finishing coat

Water Control

Sprinkle water lightly during finishing for smoother results without weakening plaster

Corner Treatment

Apply mesh at all internal corners (wall-ceiling) to prevent cracking

Hot Weather

Add set retarders to mortar, dampen surface more frequently, work during cooler hours

Surface Preparation

For smooth concrete surfaces, scratch with wire brush in crisscross pattern for better adhesion

Mortar Addition

Add small amount of lime (5-10%) to improve workability and reduce cracking

Cold Weather

Heat mixing water slightly and protect fresh plaster from freezing for at least 48 hours

Tool Maintenance

Clean tools immediately after use and oil metal surfaces to prevent rusting

12. References & Standards

13. Conclusion

By following this Standard Operating Procedure, plastering works will be executed with consistent quality, durability, and aesthetic appeal. The steps outlined ensure that the finished plaster surfaces meet structural requirements while providing excellent finished surfaces for subsequent works such as painting or tiling. Proper execution and attention to detail during each phase of plastering will result in high-quality finishes that enhance the overall construction quality and provide long-lasting protection to structural elements.

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