| S.No. | Field / Checkpoint | Reference | Status |
|---|---|---|---|
| A. BLOCK MATERIAL | |||
| A1 | Block type — solid / hollow / AAC / fly ash Acceptance: MTC + IS conformity (IS 2185 Part 1/2/4) | Per drawing | OK NC NA |
| A2 | Block strength + density + dimensions Acceptance: Lab tests / MTC verified | Per IS 2185 | OK NC NA |
| A3 | Mortar mix 1:4 / 1:5 per drawing Acceptance: Per design | Volumetric | OK NC NA |
| B. LAYING | |||
| B1 | Joint thickness 10 ± 3mm Acceptance: Joints full + tight | IS 1905 | OK NC NA |
| B2 | Vertical joints staggered ≥ 1/4 block length Acceptance: Bonding correct | Avoid running vertical joints | OK NC NA |
| B3 | Plumb + level ± 5mm per 3m Acceptance: Spirit level checked | IS 1905 | OK NC NA |
| B4 | Reinforcement (if any) in joints / cores per drawing Acceptance: Per drawing | Hollow blocks may have vertical rebar | OK NC NA |
| B5 | Lintels + RCC bands per seismic provisions Acceptance: Per drawing | IS 13828 for seismic zones III-V | OK NC NA |
| C. CURING | |||
| C1 | Curing 7 days from completion Acceptance: Continuous | Wet curing | OK NC NA |
Concrete masonry blocks (CMU — solid / hollow / AAC / fly-ash / CLC) have replaced traditional clay bricks on most modern Indian projects above 4 storeys. Reasons: faster laying (1 block ≈ 4-6 bricks), better thermal performance, lighter weight (especially AAC at ~600 kg/m³ vs brick at ~1900 kg/m³), reduced mortar consumption.
But block masonry has different failure modes than brick: - Joint discipline matters more — fewer joints means each joint carries more load - Plumb tolerance tighter — large blocks magnify any out-of-plumb at corners + reveals - AAC moisture sensitivity — over-wetting before laying causes mortar bond failure - Reinforced cells (hollow blocks) require vertical rebar + grout filling that's often forgotten - Seismic bands (RCC bands at lintel + sill + plinth + roof) mandatory in zones III-V per IS 13828
The inspection checklist is the daily quality control instrument that prevents these failures. Without it, blockwork looks OK at handover but cracks within 2-3 years (settlement / shrinkage cracks at joints, vertical cracks at unbanded corners).
Governed by IS 2185 (block specifications) + IS 1905 (workmanship) + IS 13828 (seismic provisions for low-strength masonry).
Three inspection categories:
A. Block material: - Block type specified: solid concrete (IS 2185 Part 1), hollow concrete (IS 2185 Part 1), AAC (IS 2185 Part 3), light-weight concrete (IS 2185 Part 4) - Compressive strength per design — typically 3.5 / 4 / 5 / 7.5 / 10 MPa - Density per type — solid 1800-2200 kg/m³; AAC 550-650 kg/m³ - Dimensions ± 3 mm tolerance per IS 2185 - Moisture content at delivery — AAC max 10%; concrete blocks dry - MTC (Manufacturer's Test Certificate) — strength + density + dimension certificate - Mortar mix: typically CM 1:4 (load-bearing) or CM 1:5/6 (non-load-bearing) per drawing. AAC requires thin-bed adhesive mortar (not CM) — common site mistake.
B. Laying: - Joint thickness: 10 ± 3 mm for CM mortar; 2-3 mm for AAC adhesive - Joints full + tight — no hollow joints (struck flush + tooled) - Vertical joint stagger: ≥ 1/4 block length (typically 100 mm); no running vertical joints - Plumb tolerance: ± 5 mm in 3 m height - Level tolerance: ± 5 mm in 3 m length - Corners + T-junctions properly bonded (king-closer / queen-closer arrangement) - Reinforcement in hollow cells per drawing — vertical rebar + grout fill at corners + jamb sides - Seismic bands at plinth / sill / lintel / roof levels (IS 13828) — Width = wall thickness, depth = 75-150 mm RCC, with 4 × 8 mm or 2 × 12 mm rebar - Lintels over openings — RCC or precast per drawing, with 150 mm minimum bearing - Wall ties at column-masonry interface (if RCC frame) - Holdfasts / chases for service lines pre-planned (not cut afterward)
C. Curing: - Wet curing for 7 days minimum from completion - No curing for AAC with adhesive (adhesive cures by hydration of polymers; water wash damages) - Protection from rain during 24h after laying
1. AAC blocks wet-cured like brickwork — AAC adhesive is polymer-based; water curing damages bond; site standard inherited from brickwork is wrong.
2. CM mortar used for AAC — instead of thin-bed adhesive; AAC requires 2-3 mm adhesive joint, not 10 mm CM joint; thermal bridge + thermal-mass loss.
3. Joints not staggered — running vertical joints become structural cracks in 2-3 years.
4. Hollow block cores not filled at corners — vertical rebar + grout omitted at corners + jambs; corners crack under settlement / lateral load.
5. Seismic bands omitted — projects in Delhi (Zone IV) / Guwahati / Sikkim (Zone V) without RCC bands; cracks in first earthquake.
6. Plumb error at parapet — corners go out by 25-40 mm over 3-storey wall; visible architectural defect.
7. Mortar mix not pre-measured — workers eyeball 1:6 vs design 1:4; strength weakness; later plaster doesn't adhere.
8. Block wetting overdone — concrete blocks should be barely damp; AAC should be DRY; over-wetting causes mortar bond failure.
9. Chases cut after laying — service routing not pre-planned; cutting reduces wall section + introduces cracks.
10. No bearing for window frames — frames fitted directly; later cracks at frame perimeter.
11. Wall ties to column missed — block panel walls in RCC frame need ties at every 4th course; without, panel separates from column under wind load.
Companion formats: - Brickwork Inspection Checklist (FMT-SIT-019) — for clay brick walls - Plaster Inspection Checklist (FMT-SIT-021) — finishing on top of blockwork - Material Test Report (FMT-STR-005) — block MTC - Rate Analysis Brickwork (FMT-EST-003) — companion estimation - Curing Register (FMT-SIT-025)
Codes: - IS 2185 Part 1:2005 — Concrete masonry units (hollow + solid) - IS 2185 Part 3:1984 — Autoclaved cellular (aerated) concrete masonry units - IS 2185 Part 4:2008 — Preformed foam cellular concrete blocks - IS 1905:1987 — Code of Practice for Structural Use of Unreinforced Masonry - IS 13828:1993 — Improving Earthquake Resistance of Low Strength Masonry Buildings - IS 4326:2013 — Earthquake Resistant Design and Construction of Buildings - IS 6041:2003 — Code of Practice for Construction of Autoclaved Cellular Concrete Block Masonry - IS 2212:1991 — Code of Practice for Brickwork (workmanship principles also apply to blockwork)