Code of practice for construction of RB and RBC floors and roofs

IS 10440: Scope - Key Points & Specifications

Scope Summary:

• IS 10440 covers reinforced brickwork construction including materials, workmanship, and structural requirements.
• It applies to reinforced brick roofs and floors using mild steel or deformed steel bars.
• Specifies compressive strength of masonry based on brick strength and workmanship control.

Key Table: Compressive Strength of Masonry (Clause 6.1.1)

Note: Assumed masonry strength (fm) shall not exceed the compressive strength of the mortar/grout.

Formwork (Clause 3.4)

• Formwork materials: timber or steel with adequate strength.
• Platforms made of planks/sheets supported on runners/beams.
• Props and bracing must ensure lateral stability.

Additional Notes:

• Definitions as per Clause 2.1.
• Rounding off test values per IS 2:1960 (Clause 0.4).

flowchart TD
    A[Bricks] --> B[Determine Avg. Compressive Strength]
    B --> C{Proper Control?}
    C -->|Yes| D[Use fm from 'With Proper Control' column]
    C

IS 10440 - Key Definitions & Specifications

1. Definitions (Clause 2.1)

• Standard terms related to reinforced brickwork as per IS 10440.
• Example:
  • Centering and Formwork (3.4): Timber or steel platforms/planks supported by runners/beams with props/bracings ensuring lateral stability and sufficient strength for superimposed loads.

2. Compressive Strength of Masonry (Clause 6.1.1, Table 1)

Note: fm ≤ compressive strength of mortar or grout (whichever is less).

3. Permissible Stresses (Clause 6.1.2, Table 2)

IS 10440: Key Formulas, Tables & Specifications for Materials

1. Compressive Strength of Masonry (Table 1, Clause 6.1.1)

Note: Assumed fm shall not exceed the compressive strength of mortar or grout (whichever is less).

2. Permissible Stresses in Design (Table 2, Clause 6.1.2)

IS 10440: Preliminary Work and Planning — Key Points & Specifications

1. Information Exchange (Clause 4.3):

• Ensure proper communication between floor/roof layers and other affected workers to avoid conflicts.

2. Preparatory Work (Clause 3.4):

• Formwork: Timber or steel platforms with planks/sheets on runners/beams.
• Strength: Must carry superimposed loads safely.
• Stability: Props and bracings must provide lateral stability.

3. Necessary Information for Efficient Construction (Clause 4.1 & 4.2):

• Size, dimensions, and loading conditions.
• Type and arrangement restrictions of support elements.
• Terrace level for finishes.
• Junction treatments with floors/walls.
• Roof slope and drainage provisions.
• Fixing provisions for services and ceilings.
• Provide detailed drawings and instructions to all workers involved.

Typical Formwork Arrangement (from Clause 3.4)

Summary Diagram

flowchart TD
    A[Planning & Info Exchange] --> B[Prepare Formwork]
    B --> C[Set Props & Bracing]
    C --> D[Check Load Capacity & Stability]
    D --> E[Start Floor/Roof Laying]

References:

• IS 10440 Clause 3.4, 4.1, 4.2, 4.3
• Related IS Codes for bricks, steel, and concrete reinforcement as per context.

IS 10440: Preparation and Mixing of Concrete – Key Points

• Mixing Standard: Concrete mixing shall follow IS 456:1978 guidelines (Clause 5.2).
• Concrete Grade: Minimum grade for filling and topping slabs is M15 (Clause 3.2).
• Water Content: Use just enough water for free flow without aggregate segregation.
• Aggregate Size: Select suitable aggregate size for construction needs.
• Bricks Preparation: Soak bricks in water for 4-6 hours, remove 15-20 mins before use to ensure dry skin for proper bonding (Clause 5.4).
• Formwork: Use timber or steel with adequate strength and lateral stability for formwork/platforms (Clause 3.4).

IS 456:1978 - Basic Mix Proportions for M15 Concrete

Mixing Guidelines:

• Mix cement, sand, and aggregates uniformly.
• Add water gradually to achieve workable consistency.
• Mixing time: Minimum 3 minutes in mechanical mixer or until uniform.

flowchart TD
    A[Materials: Cement, Sand, Aggregate] --> B[Batching]
    B --> C[Mixing]
    C --> D[Add Water Gradually]
    D --> E[Uniform Concrete Mix]
    E --> F[Transport & Place]

Summary: Follow IS 456 for mix design, maintain water-cement ratio ~0.6 for M15, soak bricks before use, and ensure formwork strength per IS 10440.

Key Specifications & Formulas for Design and Detailing of Reinforcement (IS 10440):

1. Reinforcement Design (Clause 6.2.1)

• Follow IS 456-1978 for design principles.
• Minimum reinforcement area:
  • Plain steel bars: ≥ 0.20% of slab cross-sectional area (A_s ≥ 0.002 × b × d)
  • High strength deformed bars: ≥ 0.16% of slab cross-sectional area (A_s ≥ 0.0016 × b × d)

2. Detailing of Reinforcement (Clause 7.2)

• Main and distribution reinforcement to be placed as per Fig.1 (RB and RBC slabs).
• Bars must be fully embedded in concrete with proper cover.
• Bars should be rigidly secured to avoid displacement.
• Stagger splices in adjacent bars to maintain structural integrity.

3. Cutting and Bending (Clause 5.3)

• Follow IS 2502-1963 for bending shapes and procedures.
• Avoid straightening bars in a way that damages them.

Typical Reinforcement Placement (Fig.1 Conceptual)

graph LR
A[Main Reinforcement] -->|Runs along length| Slab
B[Distribution Reinforcement] -->|Runs perpendicular| Slab
Slab[RB / RBC Slab Cross Section]

Summary Table for Minimum Reinforcement Area

• b = width of slab cross-section (mm)
• d = effective depth of slab (mm)

Note: Ensure formwork and centering (Clause 3.4) provide sufficient strength and lateral stability to support loads during casting.

Key Specifications for Reinforced Brick Roof/Floor (IS 10440)

1. Compressive Strength of Masonry (Clause 6.1.1)

Note: fm ≤ minimum of mortar or grout compressive strength.

2. Permissible Stresses (Clause 6.1.2)

3. Construction Notes

• High strength bricks laid over formwork with reinforcement in joints.
• Joints filled with concrete or grout.
• Corrosion protection of reinforcement is critical for durability.
• Formwork must be stable and strong

IS 10440: Inspection and Quality Control Key Points

1. Inspection (Clause 8.1)

• Inspection must be conducted at every stage to prevent unsatisfactory work.
• Ensures compliance with specifications for materials, workmanship, and structural integrity.

2. Formwork (Clause 3.4)

• Formwork should be timber or steel with sufficient strength to carry superimposed loads.
• Platforms made of planks/sheets supported on runners/beams.
• Props and bracing must provide adequate lateral stability.

3. Compressive Strength of Masonry (Clause 6.1.1, Table 1)

• Note: Assumed masonry strength fm shall not exceed the average compressive strength of mortar/grout.

4. Rounding Off (Clause 0.4)

• Results of tests/analysis should be rounded as per IS 2-1960.
• Maintain the same number of significant digits as the specified value.

Summary Diagram: Inspection & Quality Control Flow

flowchart TD
    A[Start Construction] --> B[Material Inspection]
    B --> C[Formwork Setup]
    C --> D[Reinforcement Placement]
    D --> E[Concrete/Masonry Work

IS 10440: Key Points on Curing and Finishing

1. Curing (Clause 7.5)

• Keep brickwork wet by:
  • Wet straw or wet sand cover, or
  • Gentle sprinkling of water for 24 hours after finishing.
• For slabs:
  • Water profusely.
  • Allow setting for at least 10 days.
• Finished floor/roof surfaces must be cured by watering for not less than 3 weeks (Clause 7.7).

2. Finishing (Clause 7.7)

• Apply a waterproofing course on floors/roofs:
  • Lime concrete (refer IS: 3036-1980), or
  • Mud Phuska with tiles (refer IS: 2115-1980).
• Ceilings:
  • Render/plaster after drying with:
    • Cement mortar (1:3) or
    • Lime mortar (1:2).
  • Plaster thickness: 12 mm single coat (as per IS: 1661-1972).

3. Additional Specifications

• Bricks must be soaked 4 to 6 hours, then surface dried for 15-20 minutes before use (Clause 5.4).
• Formwork must have adequate strength and lateral stability (Clause 3.4).

Summary Table

Protection Against Corrosion - IS 10440 Key Points

• Minimum Concrete Cover:
  Reinforcement shall have a minimum cover of 25 mm all around to prevent corrosion (Clause 6.2.3).

• Reinforcement Placement:
  Reinforcements must not touch bricks at any point to avoid corrosion initiation (Clause 6.2.3).

• Brick Spacing:
  Maintain a minimum spacing of 60 mm between bricks when laid with 1:3 cement mortar to ensure proper protection and ventilation (Clause 7.3).

• Reinforcement Quality:
  Reinforcement bars must conform to IS 432 (Part I)-1982, IS 1139-1966, or IS 1786-1979 and be free from rust or coatings before placement (Clause 3.3).

• Additional Measures:
  Follow recommendations in IS 9077-1979 for further corrosion protection methods (e.g., coatings, inhibitors).

Summary Table for Corrosion Protection

flowchart TD
    A[Reinforcement Bars] --> B[Clean, Rust-Free Surface]
    B --> C[Maintain 25 mm Concrete Cover]
    C --> D[Ensure No Contact with Bricks]
    D --> E[Maintain 60 mm Brick Spacing]
    E --> F[Apply Additional Measures per IS 9077]
    F --> G[Corrosion Protection Achieved]

This ensures durability and structural integrity of reinforced brick structures per IS 10440.

IS 10440: Removal of Formwork - Key Points & Specifications

1. Removal Time (Clause 7.6)

• Formwork for Reinforced Brick (RB) and Reinforced Brick Concrete (RBC) floors or roofs must not be removed before 14 days after laying.
• This ensures sufficient strength gain and avoids structural damage.

2. Formwork Requirements (Clause 3.4 & 7.1)

• Formwork must be timber or steel with adequate strength to carry all loads.
• Platforms should be planks/sheets on runners/beams.
• Props and bracings must provide lateral stability.
• Provide an upward camber of 1 mm per 150 mm span (max 30 mm) to compensate for initial settlement.
• Check formwork and supports for alignment, cleanliness, and stability before casting.

3. Compressive Strength of Masonry (Table 1, Clause 6.1.1)

Note: Assumed masonry strength (fm) must not exceed mortar or grout strength.

Summary Diagram: Formwork Removal Timeline

gantt
    title Formwork Removal Schedule (IS 10440)
    dateFormat 

IS 10440: Load and Stress Considerations for Reinforced Brick Roof/Floor

Key Specifications:

1. Compressive Strength of Masonry (fm) - Table 1 (Clause 6.1.1)

Note: fm ≤ average compressive strength of mortar or grout, whichever is less.

2. Permissible Stresses (N/mm²) - Table 2 (Clause 6.1.2)

Important Notes:

• Use fm from Table 1 based on brick strength and control quality.
• Shear stresses are limited to avoid brittle failure.
• Modulus of elasticity is capped to avoid overestimation.
• Formwork must support superimposed loads with lateral stability (Clause 3.4).

Summary Formula Examples:

• Flexural Compression Stress:
  [ \sigma_c = 0.23 \times f_m ]

• Flexural Tension Stress:
  [ \sigma_t = 0.10 \times