Cement-sand and cement-lime-sand mortar grades, with 28-day compressive strength, cement consumption per cubic metre of wet mortar, and recommended use. Richer mixes (1:3) for plinth, pointing, and waterproofing; leaner mixes (1:6, 1:8) for general brickwork above plinth.
Cement-Sand Mortar Grades
Strengths are 28-day cube tests on 1:3 sand cube (IS 2250)
| Ratio | Type | Strength | Cement / m³ | Sand / m³ | Use |
|---|
| 1:3 | MM 7.5 (rich) | 7.5 N/mm² | 440 kg / 8.8 bags | 1.0 m³ (loose) | Plinth, retaining walls, RCC pointing, water-retaining work, RR masonry below ground |
| 1:4 | MM 5.0 | 5.0 N/mm² | 340 kg / 6.8 bags | 1.0 m³ | External plaster (1st coat), brickwork in load-bearing walls, pointing |
| 1:5 | MM 3.0 | 3.0 N/mm² | 275 kg / 5.5 bags | 1.0 m³ | Internal plaster, brickwork in non-load-bearing walls |
| 1:6 | MM 2.0 | 2.0 N/mm² | 230 kg / 4.6 bags | 1.0 m³ | Brickwork above plinth (most common), single-coat plaster, ceiling plaster |
| 1:7 | MM 1.5 | 1.5 N/mm² | 200 kg / 4.0 bags | 1.0 m³ | Half-brick partitions, lean masonry |
| 1:8 | MM 1.0 (lean) | 1.0 N/mm² | 180 kg / 3.6 bags | 1.0 m³ | Filling, very low-strength masonry, compound walls |
Cement-Lime-Sand Mortar (Compound)
Lime improves workability and reduces shrinkage — popular before 1960, still used in heritage work
| Ratio | Type | Strength | Cement / m³ | Sand / m³ | Use |
|---|
| 1:1:6 | Compound MM 5.0 | 5.0 N/mm² | 230 kg | 1.0 m³ + 0.16 m³ lime | External plaster, exposed brickwork, restoration of old buildings |
| 1:2:9 | Compound MM 2.5 | 2.5 N/mm² | 150 kg | 1.0 m³ + 0.21 m³ lime | Internal plaster, finer finish on plaster |
| 0:1:3 (lime) | Pure lime | 0.7 N/mm² | 0 | 1.0 m³ + 0.33 m³ lime | Heritage/conservation only — not modern construction |
Plaster Coat Thicknesses & Mixes
| Ratio | Type | Strength | Cement / m³ | Sand / m³ | Use |
|---|
| 1:4 / 1:5 | External plaster (12 mm) | — | — | — | Single coat, external face — sand-faced finish |
| 1:6 | Internal plaster (12 mm) | — | — | — | Single coat, internal face — smooth finish |
| 1:6 | Ceiling plaster (6 mm) | — | — | — | RCC slab soffit; thinner coat |
| 1:3 + 1:4 | Two-coat external (20 mm) | — | — | — | 12 mm rough coat + 8 mm finish — for severely exposed walls |
| 1:5 | Pointing (10 mm) | — | — | — | Re-pointing exposed brickwork joints |
Notes
• Cement consumption per m³ of wet mortar = (1/(1+R)) × 1.30 × 1440 kg, where R = sand:cement ratio
• Wastage allowance: 15% for plaster, 5% for masonry mortar
• Always use the same brand of cement throughout one wall — different brands cause cracking
• Mortar must be used within 30 minutes of mixing (OPC) or 60 minutes (PPC) — never re-temper
• Sand should be sieved through 2.36 mm sieve for plaster, 4.75 mm for masonry mortar
• Add water gradually until 'flow' is right — over-watering kills strength
• For waterproof mortar, add 100 g/bag of integral waterproofing compound
• Do not use mortar richer than 1:3 — drying shrinkage causes cracks
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