IS 1077:1992 is the Indian Standard (BIS) for common burnt clay building bricks - specification. This standard specifies the dimensions, quality, classification, and physical requirements (such as compressive strength, water absorption, and efflorescence) for common burnt clay building bricks. It is universally used by engineers and contractors for quality control of bricks on construction sites.
Specifies dimensions, quality, and physical requirements for common burnt clay building bricks.
Key values for brick classification, dimensional tolerances, strength, water absorption, efflorescence, and sampling criteria.
| Reference | Value | Clause |
|---|---|---|
| Standard Brick Size | 190 x 90 x 90 mm | Cl. 7.1 |
| Standard Thin Brick Size | 190 x 90 x 40 mm | Cl. 7.1 |
| Dim. Tolerance (Length of 20 bricks)— On a total specified length of 3800 mm | ±40 mm | Cl. 7.2 (Table 1) |
| Dim. Tolerance (Width of 20 bricks)— On a total specified width of 1800 mm | ±20 mm | Cl. 7.2 (Table 1) |
| Dim. Tolerance (Height of 20 bricks)— For 90 mm high bricks; on a total specified height of 1800 mm | ±20 mm | Cl. 7.2 (Table 1) |
| Warpage (Max Concavity / Convexity) | 3 mm | Cl. 7.3 |
| Frog Depth (Max) | 20 mm | Cl. 7.4 |
| Compressive Strength Class Range— Value indicates min. average strength in N/mm² (MPa) | 3.5 to 35 | Cl. 4.1 (Table 2) |
| Min. Avg. Compressive Strength (Class 10) | 10.0 N/mm² | Cl. 8.1 (Table 2) |
| Min. Avg. Compressive Strength (Class 7.5) | 7.5 N/mm² | Cl. 8.1 (Table 2) |
| Min. Avg. Compressive Strength (Class 5) | 5.0 N/mm² | Cl. 8.1 (Table 2) |
| Individual Brick Strength Limit— Strength of any brick shall not be < 80% of the class average | ≥ (0.80 x Class Avg. Strength) | Cl. 8.1.1 (Amd. 4) |
| Max Water Absorption (Class ≤ 12.5)— After 24-hour cold water immersion | 20 % by mass | Cl. 8.2 |
| Max Water Absorption (Class > 12.5)— After 24-hour cold water immersion | 15 % by mass | Cl. 8.2 |
| Max Efflorescence (Class ≤ 12.5)— Deposit covers >10% but ≤50% of brick face area | Moderate | Cl. 8.3.2 |
| Max Efflorescence (Class > 12.5)— Deposit covers ≤10% of brick face area | Slight | Cl. 8.3.2 |
| Lime Blowing Check— After immersion in water for 24 h | No signs of disintegration | Cl. 6.1.1 |
| Sample Size (Lot: 2,001-10,000) | 10 bricks | Cl. 9.2.1 (Table 3) |
| Sample Size (Lot: 10,001-35,000) | 15 bricks | Cl. 9.2.1 (Table 3) |
| Sample Size (Lot: 35,001-50,000) | 20 bricks | Cl. 9.2.1 (Table 3) |
IS 1077 specifies common burnt clay building bricks — the workhorse masonry unit for residential, commercial, and industrial construction in India. Despite the rise of concrete blocks, AAC blocks, and fly-ash bricks, burnt clay brick remains the most-produced masonry unit in India (estimated 250-350 billion bricks annually).
Use IS 1077 when specifying brick for: - Load-bearing brick masonry (single / two-storey residential) - Brick infill walls in RCC framed buildings - Boundary walls, compound walls, retaining walls - Decorative facing brickwork - Sewer / drain lining (acid-resistant variants) - Pavers (separate code IS 15658)
IS 1077 covers classes of clay bricks by compressive strength, ranging from low-load common bricks to high-strength engineering bricks.
Alternatives to IS 1077 burnt clay brick: - IS 12894:2002 — fly ash-clay bricks - IS 2185 Part 1 — solid concrete blocks - IS 2185 Part 3 — autoclaved cellular concrete blocks (AAC) - IS 13757 — burnt clay perforated bricks - IS 12440 — precast concrete blocks for paving (kerbs)
Classes by compressive strength (Clause 5):
| Class | Min average compressive strength (N/mm²) | Use | |---|---|---| | Class 35 | 35.0 | Engineering brick — high-load (rare) | | Class 30 | 30.0 | Engineering / loadbearing | | Class 25 | 25.0 | Loadbearing | | Class 20 | 20.0 | Loadbearing | | Class 17.5 | 17.5 | Loadbearing | | Class 15 | 15.0 | Loadbearing (medium) | | Class 12.5 | 12.5 | Loadbearing (light) | | Class 10 | 10.0 | Common (non-loadbearing / infill) | | Class 7.5 | 7.5 | Common (light infill) | | Class 5 | 5.0 | Light common brick | | Class 3.5 | 3.5 | Very light (rare) |
Acceptance: average of 5 bricks tested per IS 3495 ≥ specified class strength; no individual < 80 % of average.
Standard dimensions (modular brick, Clause 4): - Length: 190 mm (effective brick); 200 mm (with mortar joint of 10 mm) - Width: 90 mm (effective); 100 mm (with mortar) - Height: 90 mm (effective); 100 mm (with mortar) - Mass: ~3.5-4.5 kg per brick
Traditional / non-modular brick (still common): - Length: 230 mm; Width: 110 mm; Height: 70-75 mm - Mass: ~3.0-3.5 kg per brick - Used in northern India (Gangetic plain)
Tolerances (Clause 6): - Length: ±3 mm - Width: ±2 mm - Height: ±2 mm - Variation in any one dimension within sample of 20 bricks: max 5 mm
Other physical properties: - Water absorption: ≤ 20 % (by mass) for Class 12.5+; ≤ 22 % for lower classes (per IS 3495 Part 2) - Efflorescence: 'nil' to 'slight' acceptable; 'moderate' / 'heavy' / 'serious' rejected (Clause 8.2) - Soundness (frost / weathering test): pass per IS 3495 Part 3 for cold-zone exposure - Warpage: ≤ 3 mm (loadbearing); ≤ 5 mm (common)
Brick masonry strength (per IS 1905:1987):
| Brick class | Mortar (cement-sand) | Brick masonry strength (N/mm²) | |---|---|---| | Class 10 | 1:6 | 1.5-2.0 | | Class 15 | 1:6 | 2.5-3.0 | | Class 20 | 1:4 | 3.5-4.5 | | Class 25 | 1:4 | 4.5-5.5 | | Class 30+ | 1:3 | 6.0-8.0 |
Masonry strength typically 20-35 % of brick strength + mortar contribution.
Mortar mixes for brickwork: - 1:6 (cement:sand) — non-loadbearing partition, infill - 1:5 — moderate-load loadbearing single storey - 1:4 — high-load loadbearing - 1:3 — engineering masonry, high-strength - 1:2 — very high-strength (rare)
Lime-cement mortars: - 1:1:6 (cement:lime:sand) — flexible mortar for old / heritage masonry - 1:2:9 — very lean mortar for non-structural
Brick consumption (per cubic metre of brickwork): - Modular brick (190 × 90 × 90 mm): ~500 bricks/m³ - Traditional brick (230 × 110 × 75 mm): ~430 bricks/m³ - With 10 % wastage allowance: 550 / 470 bricks/m³
Mortar consumption: - 1:6 cement-sand mortar: ~0.30 m³ per m³ of brickwork (modular brick) - 1:4 mortar: same volume but more cement
Brickwork dead load: - 9-inch (230 mm) brick wall: ~4.0-4.5 kN/m² (≈ 400-450 kg/m²) - 4.5-inch (110 mm) brick wall: ~2.0-2.3 kN/m² - Plaster on both sides: add ~0.5 kN/m² (12 mm cement plaster each face)
Test sample size: - Per IS 3495 Part 1 / 2: 20 bricks per 50,000 bricks lot for compressive strength + water absorption - Per IS 3495 Part 4: 5 bricks for efflorescence test
Common pitfalls: - Sampling from top of stack (best bricks at top). Sample randomly. - Excessive water absorption (>20 %) makes brick weak in wet conditions; pre-soak before laying.
1. Random brick procurement without class verification. Brick yards often mix classes; supplied 'first-class' brick may be Class 7.5 (not Class 15). Test per IS 3495 at delivery. 2. No water absorption test. > 20 % absorption = brick is weak when wet; load-bearing wall fails earlier than design. Mandatory test at source qualification. 3. Efflorescence on completed walls. White salt deposits from soluble salts in brick + cement; aesthetics + degradation. Test brick efflorescence at source; reject 'serious' graded. 4. Bricks not pre-soaked before laying. Dry brick absorbs mortar water; mortar weak; bond poor. Soak bricks in water for 30-60 minutes before laying. 5. Inadequate mortar curing. Brickwork cured for ≥ 7-14 days; without curing, mortar shrinks, cracks, separates from brick. 6. Mortar mix wrong for class. Class 25 brick + 1:6 mortar = under-utilised brick (mortar governs); Class 7.5 brick + 1:3 mortar = over-design (waste of cement). Match mortar to brick class. 7. Joint thickness inconsistent. Standard 10 mm; varies 6-15 mm in poor workmanship; affects masonry strength + appearance. Use mortar gauge. 8. Half-brick (4.5") wall used as load-bearing. 110 mm brick wall is non-load-bearing in IS 1905:1987; needs 230 mm minimum for load-bearing. 9. No reinforcement / RCC band in seismic zones. Per IS 4326:1993, unreinforced masonry in Zones III-V needs RCC plinth band, lintel band, gable band, vertical reinforcement at corners. Skipping = collapse in earthquake. 10. Brick stacking on side / damaged during transport. Edges chip, surface damage; reduces effective area + crack-initiation. Stack flat, transport with cushioning. 11. Used / reclaimed brick re-used without testing. Strength lost over time + thermal cycles; cannot assume original class. Test before re-use. 12. Hollow / perforated brick used where solid was specified. Different strength + thermal + fire properties. Verify specification.
Brick masonry construction cascade:
1. Design (IS 1905:1987) — masonry strength, wall thickness, openings, lintels. 2. Material specification: - Brick class per loadbearing requirement (this code, IS 1077) - Mortar mix per masonry strength target - Reinforcement per IS 4326 seismic requirements 3. Source qualification: - Brick test per IS 3495 (compressive strength, water absorption, efflorescence, warpage) - Mortar trial mixes - Sample wall trial (3 m² panel) 4. Delivery acceptance: - Visual: edge sharpness, colour uniformity, no visible cracks - Random sample test: 20 bricks per 50,000 lot - Efflorescence check 5. Laying: - Pre-soak bricks (30-60 min) - Mortar mix at OMC - Standard joint thickness (10 mm) - English / Flemish bond as specified - Plumb + level + line check daily 6. Curing: - 7-14 days water curing - Avoid drying winds, direct sun on fresh masonry 7. Reinforcement / bands (seismic zones): - RCC plinth band, lintel band, gable band - Vertical reinforcement at corners + jambs of openings 8. Plaster / finish (after curing): - 12 mm cement plaster (1:6 typical) - Curing of plaster 7-14 days 9. Quality acceptance: - Plumb, level, line tolerance check - Joint thickness uniformity - Crack-free (cracks > 0.3 mm rejection) 10. Long-term performance — periodic inspection for damp, salt deposits, cracking; repointing every 30-50 years for exposed face brickwork.
IS 1077 has been the foundation of Indian brick masonry for decades. Modern building practice supplements with NBC 2016 and IS 4326 seismic requirements; the brick itself remains the workhorse masonry unit.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Primary Classification Basis | Compressive Strength (in N/mm²) | Weathering Resistance (Grade SW, MW, NW) | ASTM C62-17 |
| Minimum Compressive Strength (Lowest Class) | 3.5 N/mm² (average for Class 3.5) | 10.3 N/mm² (minimum for an individual brick, Grade NW) | ASTM C62-17 |
| Maximum Water Absorption (24-hr cold soak) | 20% by mass (for classes up to 12.5) | 22.0% by mass (average for Grade MW) | ASTM C62-17 |
| Standard 'Non-Modular' Size | 230 x 110 x 70 mm | No single standard size; defined by manufacturer. (e.g., UK common: 215 x 102.5 x 65 mm) | BS EN 771-1:2011+A1:2015 |
| Efflorescence Requirement | Required test with graded limits (e.g., 'Moderate' rating is permissible for common bricks) | Optional; must be specified by the purchaser | ASTM C62-17 |
| Dimensional Tolerance (Length, typical) | ±3% (for Class > 12.5) | Tolerance is declared by the manufacturer under categories (e.g., T2, Tm) | BS EN 771-1:2011+A1:2015 |
| Soluble Salt Content Limit | Not to exceed 0.1% by mass | Active soluble salt content categories are S1 or S2, based on the content of Na+, K+, Mg2+ | BS EN 771-1:2011+A1:2015 |