- 1. Introduction
- 2. Manufacturing and composition
- 3. Types and recommended mixes
- 3A. Pointing systems (masonry joints)
- 4. Surface preparation and bonding
- 5. Application methodology
- 6. Properties and target performance
- 7. Common defects and remedies
- 8. QA and testing
- 9. Specification snippets
- Disclaimer
Purpose: consultant-ready guide to plasters, renders, and pointing systems. Use the TOC to jump to types and mixes, manufacturing, surface preparation, defects and fixes, QA tests, and specification. Clean, print-ready (Word-friendly) format.
1. Introduction
Plaster, render, and pointing systems form the protective envelope of masonry and concrete. They improve durability, weather resistance, and appearance, and provide a substrate for finishes.
2. Manufacturing and composition
- Ready-mix plaster and render
- Factory blending of cement, graded sand, polymers, and additives
- Controlled batching for consistency
- Supplied in 40–50 kg bags for on-site water addition
- Site-mixed cement-sand systems
- Use washed, well-graded sand (Zone II for internal; coarser Zone I for external scratch coats)
- Maintain measured proportions (prefer weight-based)
3. Types and recommended mixes
System | Mix / system | Typical thickness | Application |
Internal cement plaster | CM 1:6 | 12 mm (2 coats: scratch + finish) | Internal walls and ceilings |
External cement render | CM 1:4 | 15–20 mm (scratch + finish) | Weather-resistant facades |
Waterproof render | CM 1:4 + integral waterproofing | 15–20 mm | Balconies and wet-exposed areas |
Polymer-modified plaster (PMM) | Proprietary PMM | 10–15 mm | Damp-prone zones; improved adhesion/flexibility |
Ready-mix plaster/render | Factory-made | As per TDS | Consistency and speed on large works |
Gypsum plaster | Ready use | 8–12 mm | Internal dry walls only |
3A. Pointing systems (masonry joints)
Pointing type | Material / mix | Use case |
Flush pointing | CM 1:3 to 1:4 or PMM | General exterior where paint/render follows |
Weathered (struck) pointing | CM 1:3 to 1:4 or PMM | Rain-exposed facades; sheds water |
Recessed pointing | CM 1:3 to 1:4 or PMM | Architectural finish; pair with breathable sealers |
V-groove / keyed | PMM or cementitious with bonding agent | Decorative; improved durability |
4. Surface preparation and bonding
- Remove loose material, dust, laitance, efflorescence, oil, and curing compounds
- Masonry: pre-wet to saturated surface dry to control suction; avoid free water
- Concrete/low-suction surfaces: apply bond coat (cement + SBR slurry) or proprietary primer
- Mesh reinforcement: across dissimilar substrates and wide panels to control cracking
5. Application methodology
- Mark control dots and screeds for thickness
- Scratch coat then finish coat; keep scratch surface rough for key
- Work in lifts suited to pot life; avoid over-trowelling wet layers
- Pointing: rake joints 10–12 mm, clean, pre-wet, compact mortar, finish profile; cure 3–5 days
- Curing: commence after initial set; maintain moisture for at least 7 days for cementitious systems
6. Properties and target performance
Property | Test method | Target range | Notes |
Compressive strength (28 days) | IS 516 or product TDS | 6–10 MPa (cementitious) | Varies by system and layer |
Adhesion (pull-off) | ASTM C952 or equivalent | >= 0.5 N/mm2 | Critical for PMM/ready-mix |
Water absorption | IS 2645 or product method | <= 10% for waterproof renders | Use integral compounds |
Drying shrinkage | ASTM C157 | <= 0.05% | Fibers/polymers reduce shrinkage |
7. Common defects and remedies
Defect | Reason | Remedy |
Cracking | High w/c, rapid drying, excessive thickness | Reduce w/c; shade and cure; control thickness; add fibers/mesh |
Delamination / peeling | Poor key or contaminated substrate | Bond coat/primer; mechanical key; surface preparation |
Hollow sound / blistering | Entrapped air; over-trowelling | Proper compaction; avoid overworking |
Efflorescence | Moisture with soluble salts | Eliminate moisture source; breathable sealer |
Pointing fall-out | Insufficient raking; poor suction control | Rake 10–12 mm; SSD pre-wet; use PMM/bond coat |
8. QA and testing
- Thickness gauge checks per panel
- Adhesion pull-off tests as required
- Ponding tests for balcony/wet-area renders: 72 hours without leakage
- Environmental limits: avoid application at relative humidity > 85% or on saturated surfaces
9. Specification snippets
- External render: Two coats to total 18 mm using polymer-modified cement render over prepared masonry. Provide bond coat over RCC bands. Cure minimum 7 days. Finish true and level.
- Internal plaster: 12 mm thick CM 1:6, two coats, smooth finish. Cure minimum 7 days.
- Pointing: Rake joints to 10–12 mm; provide polymer-modified mortar pointing with [flush/weathered/recessed] profile; cure minimum 3 days.
Disclaimer
Conix is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.