Code of practice for construction of lightweight concrete block masonry
1969 Edition

Scope Overview of IS 6042

• Scope Description: Specifies requirements for load-bearing masonry using lightweight concrete blocks and lime-cement cinder solid blocks.

• Work Execution Details (Clause 3.1):

  • Layout plans including walls, doors, windows, stairs, columns.
  • Precise dimensions and sectional drawings.
  • Architectural elements and embedded fixtures.
  • Details of embedded conduits, piping, and ducts.

• Construction Scheduling (Clause 4.3):

  • Timeframes for supplying drawings, material procurement, and construction milestones.

• Maintenance Guidelines (Clause 12.1):

  • Annual inspections prior to monsoon season.
  • Repair of cracks using cement grout.
  • Application of two coats of cement-based paint on exposed masonry surfaces.

Typical Block Specification Summary:

Planning Flowchart for Masonry Work

flowchart TD
    Start[Project Initiation] --> Layout[Develop Layout Plans]
    Layout --> Dimensions[Specify Structural Dimensions]
    Dimensions --> Details[Architectural & Embedded Details]
    Details --> Schedule[Plan Material Delivery & Construction]
    Schedule --> Execution[Carry Out Masonry Work]
    Execution --> Maintenance[Annual Inspection & Upkeep]

Note: For comprehensive block dimensions, mix ratios, and testing procedures, consult the full IS 6042 document and related Indian Standards on masonry units.

Essential Definitions in IS 6042

Moisture Movement (Clause 2.4)

• Defined as the percentage change in length between a specimen dried to constant length and saturated with water:

[ \text{Moisture Movement (%)} = \frac{L_{wet} - L_{dry}}{L_{dry}} \times 100 ]

Required Data for Work (Clause 3.1)

• Layout drawings covering walls, doors, windows, stairs, and columns.
• Detailed structural dimensions and sectional information.
• Architectural features and embedded fixtures.
• Embedded services such as conduits, pipes, and ducts.

Joint Reinforcement Spacing to Prevent Cracking (Clause 7.5.5.3)

Diagram: Joint Reinforcement Spacing

graph LR
    WallPanel[Wall Panel] --> Spacing{Joint Reinforcement Spacing}
    Spacing --> S600[600 mm: Length ≤ 12.5 m, L/H ≤ 2.5]
    Spacing --> S400[400 mm: Length ≤ 15 m, L/H ≤ 3]
    Spacing --> S200[200 mm: Length ≤ 18 m, L/H ≤ 4]

Note: Adhering to these spacing guidelines controls crack formation and maintains wall stability.

Key Data Requirements as per IS 6042

Clause 3.1: Data for Efficient Work Planning

• Layout Plans: Details of walls, openings, stairs, and columns.
• Structural Dimensions: Precise measurements and sectional views.
• Architectural Features: Mouldings, embedded fixtures.
• Embedded Utilities: Electrical conduits, plumbing, HVAC ducts.

Moisture Movement Concept (Clause 2.4)

• Calculated as (Length saturated - Length dry) divided by Length dry, multiplied by 100.
• Expressed as a percentage, crucial for dimensional stability.

Joint Reinforcement Spacing to Minimize Cracks (Clause 7.5.5.3)

• Closer spacing enhances crack control effectiveness.

Workflow Diagram for Masonry Information

flowchart TD
    Start[Project Start] --> Layout[Acquire Layout Plans]
    Layout --> Dimensions[Obtain Structural Dimensions]
    Dimensions --> Features[Detail Architectural Elements]
    Features --> Services[Specify Embedded Services]
    Services --> Reinforcement[Design Joint Reinforcement]
    Reinforcement --> Execution[Perform Masonry Construction]

This approach complies with IS 6042 requirements for structural integrity and crack management.

Preparations According to IS 6042

Planning Data (Clause 3.1)

• Detailed layout including all walls, openings, stairs, columns.
• Accurate structural section dimensions.
• Architectural details such as mouldings and fixtures.
• Embedded utilities like electrical conduits, water pipes, and air ducts.

Handling and Storage of Materials (Clause 8.2)

• Follow relevant standards (e.g., IS 269 for cement) for storing cement, lime, and aggregates.

Mortar Preparation (Clause 6.3)

• Mortar prepared following IS 2250:1965 guidelines.
• Mortar consistency tested by slump method with a target slump of 75 mm (IS 1199:1959).

Construction Scheduling (Clause 4.3)

• Must include dates for drawings supply, materials arrival, and masonry work start and completion.

Mortar Mix Reference Table (from IS 2250)

Preparatory Work Flow

flowchart TD
    Begin[Start Preparations] --> Layout[Gather Layout & Dimensions]
    Layout --> Features[Note Architectural & Embedded Details]
    Features --> Schedule[Plan Material Supply & Work Timeline]
    Schedule --> Storage[Store Materials per IS Guidelines]
    Storage --> Mortar[Prepare Mortar as per IS 2250]
    Mortar --> Masonry[Commence Masonry Construction]

This systematic preparation ensures compliance and efficient masonry work.

Material Requirements Based on IS 6042

Storage and Handling (Clause 8.2)

• Cement, lime, aggregates, and masonry materials must be stored in accordance with applicable IS standards such as IS 269 (cement) and IS 1542 (lime).
• Storage areas must be dry and materials stacked to prevent contamination and moisture damage.

Mortar Preparation (Clause 6.3)

• Mortar must conform to IS 2250:1965.
• Slump test for mortar should target 75 mm (per IS 1199:1959).

Relevant Material Standards

• Building lime specifications updated per IS norms.
• Aggregates conform to IS 383.
• Sand for masonry mortars as per IS 2116.
• Pozzolanic materials like fly ash conform to respective IS standards.

Joint Reinforcement Spacing (Clause 7.5.5.3)

Summary Flow

flowchart TD
    Materials[Cement, Lime, Aggregates] --> Storage[Proper Storage & Handling]
    Storage --> Mortar[Mortar Preparation per IS 2250]
    Mortar --> Slump[Ensure 75 mm Slump]
    Slump --> Reinforcement[Apply Joint Reinforcement per Clause 7.5.5.3]
    Reinforcement --> CrackControl[Prevent Cracking]

Following these ensures durable masonry construction aligned with IS 6042.

Mortar Mix Guidelines for Lightweight Concrete Blocks per IS 6042

• Typical Mortar Ratios:

  • Standard: 1 part Cement : 2 parts Lime : 9 parts Sand.
  • For high load or harsh exposure: 1 part Cement : 1 part Lime : 6 parts Sand.
  • When quality lime is unavailable: 1 part Cement : 6 parts Sand.

• Rationale: Mortar strength is intentionally kept lower than block strength to reduce cracking risks.

• Application Instructions:

  • For exposed faces, rake out mortar joints to a depth of 20 mm and refill with a caulking compound.
  • On unexposed sides, alternate mortar and caulking compound in joints.
  • Install 5 mm greased wire reinforcement in every alternate course.
  • Wire reinforcement is bent in U-shapes for pilasters and control joint areas.

Mortar Mix Summary Table

Reinforcement and Joint Treatment Diagram

flowchart LR
    ExposedFace[Exposed Face] --> Rake[Remove Mortar 20 mm]
    Rake --> Fill[Fill with Caulking Compound]
    UnexposedFace[Unexposed Face] --> Alternate[Alternate Mortar and Caulking]
    EveryAlternateCourse --> Wire[5 mm Greased Wire Reinforcement]
    Wire --> Pilasters[Wire Bent in U-shape for Pilasters]

Reference: IS 6042 Clauses 6.2, 10.1.1. Block density limited to ≤ 1000 kg/m³ as per IS 3590-1966.

Structural Design and Reinforcement Guidelines per IS 6042

Bond Beams and Studs (Clause 7.3)

• Bond beams can be either structural or non-structural.
• Non-structural bond beams provide continuous tensile resistance along walls.
• Structural bond beams and studs are designed to carry loads and resist bending and tension stresses.

Crack Prevention via Joint Reinforcement Spacing (Clause 7.5.5.3)

• Closer reinforcement spacing improves crack resistance.

Lateral Support Provisions (Clause 7.2.3.1)

• Horizontal or vertical lateral supports must be installed perpendicular to the wall.
• Such supports include cross walls, pilasters, sealed bonds, buttresses, floors, and roofs.
• Spacing of these supports must be controlled to prevent buckling.

Key Design Parameters Table

flowchart TD
    WallPanel[Wall Panel] --> JointReinf[Joint Reinforcement Spacing]
    JointReinf -->|200 mm| MaxLength18[Max Length 18 m, L/H=4]
    JointReinf -->|400 mm| MaxLength15[Max Length 15 m, L/H=3]
    JointReinf -->|600 mm| MaxLength12_5[Max Length 12.5 m, L/H=2.5]

This ensures the masonry wall's structural integrity and crack resistance.

Material Storage and Handling Requirements in IS 6042

Block Storage (Clause 8.1)

• Store blocks elevated off the ground using planks or supports.
• Protect blocks from moisture exposure by covering with waterproof sheeting.
• Avoid direct contact of blocks with wet or damp surfaces to prevent degradation.

Storage of Cement, Lime, and Aggregates (Clause 8.2)

• Follow applicable Indian Standards (e.g., IS 269 for cement) for storage practices.
• Store materials in dry, covered areas with proper stacking to avoid moisture and contamination.

Control Joint Locations (Clause 7.5.6.2)

Control joints accommodate wall movement and reduce cracking:

Storage and Control Joint Summary Diagram

flowchart TD
    BlockStorage[Block Storage] --> Elevated[Store Off Ground on Supports]
    Elevated --> Covered[Cover to Prevent Moisture]
    BlockStorage --> NoGroundContact[No Direct Ground Contact]
    ControlJoints[Control Joints] --> HeightChange[At Wall Height/Thickness Changes]
    ControlJoints --> ConstructionJoints[At Construction Joints]
    ControlJoints --> Recesses[At Recesses and Chases]
    ControlJoints --> Abutments[At Wall-Column Abutments]
    ControlJoints --> Returns[At Return Angles]
    ControlJoints --> Openings[At Wall Openings]

Note: Refer to IS 269, IS 383, and IS 2185 for detailed storage, stacking, and handling procedures.

Preparatory Requirements According to IS 6042

Essential Information for Project Planning (Clause 3.1)

• Layout details including walls, doors, windows, openings, stairs, and columns.
• Structural dimensions and section drawings.
• Architectural details including mouldings and embedded fittings.
• Embedded services such as electrical conduits, sanitary pipes, water supply, and HVAC ducts.

Material Storage and Handling (Clause 8.2)

• Store and transport cement, lime, aggregates, and masonry units according to relevant IS codes, e.g., IS 269 for cement.

Mortar Mixing (Clause 6.3)

• Mortar should be prepared as per IS 2250:1965.
• Target a mortar slump of 75 mm as per IS 1199:1959.

Scheduling Construction Activities (Clause 4.3)

• Include timelines for drawing/specification delivery, material procurement, and masonry construction phases.

Reference Indian Standards Table

Preparatory Work Flowchart

flowchart TD
    Prep[Preparatory Work] --> Layout[Layout Plans]
    Prep --> Storage[Material Storage]
    Prep --> Mortar[Mortar Preparation]
    Prep --> Schedule[Work Scheduling]
    Layout --> Walls[Walls, Doors, Windows]
    Layout --> Sections[Sections & Dimensions]
    Layout --> Embedded[Embedded Services]
    Mortar --> Mix[IS 2250 Mortar Mix]
    Mortar --> Slump[Slump 75 mm]
    Schedule --> Drawings[Drawings & Specifications]
    Schedule --> Delivery[Material Delivery]
    Schedule --> Timeline[Construction Timeline]

This ensures smooth and compliant masonry construction.

Laying Operations for Lightweight Concrete Block Masonry as per IS 6042 (Clause 10.2)

Important Practices:

• Mortar Mix:

  • Use mortar ratios of either 1:2:9 (cement:lime:sand) or 1:1:6 (cement:lime:sand).
  • If lime is poor quality, utilize 1:6 (cement:sand) mortar.

• Alignment:

  • Stretch a mason’s line corner to corner for each course.
  • Align the top outer edge of each block to this line.
  • Handle blocks carefully to avoid repositioning after placement.

• Control Joints and Reinforcement:

  • Rake out mortar joints on exposed faces to 20 mm depth and fill with caulking compound.
  • Insert 5 mm greased wire reinforcement in every alternate course.
  • Wires may be bent in a "U" shape for pilasters and control joints.
  • On unexposed faces, alternate mortar and caulking compound joints.

Mortar Mix Summary

Visual Flow: Control Joints and Wire Reinforcement

flowchart LR
    CornerBlocks[Corner Blocks] --> Line[Mason's Line Stretched]
    Line --> Align[Blocks Laid to Line]
    Align --> Wire[5 mm Greased Wire in Alternate Courses]
    Wire --> ExposedFace[Exposed Face: Mortar Raked 20 mm]
    ExposedFace --> Caulking[Fill with Caulking Compound]
    Wire --> UnexposedFace[Unexposed Face: Alternate Mortar or Caulking]

Note: Correct alignment and joint treatment are crucial for durability and crack resistance.

Guidelines for Rendering and Finishes per IS 6042

External Rendering (Clauses 11.1 & 11.1.1)

• Purpose: To provide waterproof protection to lightweight concrete block walls.
• Conditions: Apply only on dry walls, avoiding monsoon or damp conditions.
• Mortar: Use plaster mix per IS 2402-1963 with sand graded up to 3 mm.
• Thickness & Finish: Backing coat of 15 mm, finishing coat between 5 to 10 mm; finish with a coarse texture using a wooden float.

Recommended Mortar Mix for Heavy Rain or Coastal Exposure

Internal Rendering (Clause 11.2)

• For exposed block surfaces, apply flush pointing followed by paint (cement-based, emulsion, or chlorinated rubber).
• Avoid oil-based paints due to alkali reaction.
• For plastered finishes, apply a 6 to 12 mm thick coat of 1:2:9 mortar; optionally, a second coat (2-3 mm) of lime finish for smoothness.

Additional Considerations

• Long side walls require pilasters or sealed bonds approximately twice the wall thickness for stiffness (Clause 10.6.3).
• Proper sand grading and plaster texture are key to longevity and appearance.

flowchart TD
    ExternalWalls[External Walls] --> Rainfall{Rainfall Intensity}
    Rainfall -->|Heavy/Coastal| TwoCoats[Two-Coat Rendering]
    Rainfall -->|Light/Moderate| PaintOnly[Single Coat or Paint Finish]
    TwoCoats --> Backing[Backing Coat: 15 mm, 1:1:6 or 1:6]
    TwoCoats --> Finishing[Finishing Coat: 5-10 mm, 1:1:6 to 1:2:9]
    PaintOnly --> FlushPoint[Flush Point + Paint]

This ensures effective waterproofing and weather resistance of lightweight block masonry.