Code of practice for design and construction of stone slab over joist floor

IS 2792: Introduction - Key Points

1. Types of Stones

• Refer to IS 1805-1961 for descriptions of various stone types.

2. Finishing of Stone Floors (Clause 11.1)

• Stone floors can be finished with:
  • Cement plaster (1:3 mix), 20 mm thick
  • Other finishes as per relevant IS codes:

3. Necessary Information for Design (Clause 3.1)

• Dimensions of area
• Type of supporting structure
• Level of walls/supports for floor
• Treatment at junctions with walls/floors
• Provisions for slopes, fixing services, ceilings

4. Permissible Stresses in Stone Slabs (Clause 4.2.1)

• Max permissible bending stress = 1/10 of ultimate transverse strength (IS 1121-1957)
• Typical permissible stresses:

Summary Diagram: Stone Floor Design Considerations

graph TD
A[Stone Floor Design] --> B[Stone Type (IS 1805)]
A --> C[Supporting Structure]
A --> D[Floor Level & Junctions]
A --> E[Floor Finishing (IS 1443, 2114, 2115, 1196)]
A --> F[Permissible Stress (IS 1121)]

This covers the essential introductory specifications and references for stone flooring as per IS 2792.

IS 2792 - Scope (Clause 3.1 & 3.2)

Key Information Required for Design & Construction:

• Dimensions of the area to be covered.
• Type of supporting structures and any restrictions.
• Level of walls/supports to receive the floor.
• Treatment at junctions with adjacent floors, walls, etc.
• Provisions in walls/supports for slopes, fixing services, ceiling, etc.

All this info must be communicated clearly to designers and constructors with necessary drawings (Clause 3.2).

Finishing Specifications (Clause 11.1)

Stone floors may be finished with:

Summary Diagram of Scope Information Flow

flowchart TD
    A[Start: Project Planning] --> B[Gather Dimensions & Area]
    B --> C[Identify Support Structures & Restrictions]
    C --> D[Determine Level of Supports/Walls]
    D --> E[Plan Junction Treatments]
    E --> F[Design Provisions for Slopes & Fixings]
    F --> G[Prepare Drawings & Instructions]
    G --> H[Communicate to Designers & Constructors]
    H --> I[Construction & Finishing]

Note: Refer to IS 1805 for stone types and related properties.

This ensures a systematic approach to floor design and finishing in stone flooring works per IS 2792.

IS 2792 - Necessary Information for Stone Flooring

Key Information Required (Clause 3.1)

For efficient design and construction, provide:

• a) Dimensions of the area to be covered.
• b) Type of supporting structures and any restrictions.
• c) Level to which walls/supports must be raised for flooring.
• d) Treatment details at junctions with adjacent floors, walls.
• e) Provisions in walls/supports for slopes, fixing services, ceiling, etc.

Instructions (Clause 3.2)

• Share all above info with design and construction teams.
• Provide necessary drawings and preparatory instructions.

Finishing Specifications (Clause 11.1)

Stone floors may be finished with:

* Codes are for laying and finishing practices.

Summary Diagram: Necessary Information Flow

flowchart TD
    A[Project Scope] --> B[Dimensions of Area]
    A --> C[Supporting Structure Details]
    A --> D[Level of Walls/Supports]
    A --> E[Junction Treatments]
    A --> F[Provisions for Slopes & Fixings]
    B & C & D & E & F --> G[Design & Construction Teams]
    G --> H[Drawings & Instructions]

References:

• IS 2792: Stone Flooring Code
• IS 1805: Stone Types
• Relevant IS codes for finishes as above.

Design Considerations - IS 2792 Summary

Key Points from Clauses 3 & 4:

• Information Exchange (3.3): Coordination is essential between floor layers and other trades affecting or affected by the floor.

• Design Inputs (3.1 & 3.2): Provide detailed info on:

  • Area dimensions
  • Supporting structure type & constraints
  • Wall/support levels for floor placement
  • Junction treatments with walls/floors
  • Provisions for slopes, services, ceiling fixing

• Joist Design (4.2.3): Joists act as beams supporting dead + live loads (per IS 875-1964). Design must follow relevant IS codes:

Typical Load Calculation for Joists:

[ \text{Total Load} = \text{Dead Load} + \text{Live Load} ]

• Dead Load: Weight of stone floor, concrete, finishing.
• Live Load: As per IS 875 (varies per usage).

Design Steps:

1. Calculate total load per unit area.
2. Determine joist spacing & span.
3. Design joist as beam using bending moment and shear formulas.
4. Check deflection limits and stability.

flowchart TD
    A[Gather Design Data] --> B[Calculate Loads (Dead + Live)]
    B --> C[Select Joist Material & Span]
    C --> D[Design Joist as Beam (IS Codes)]
    D --> E[Check Deflection & Stability]
    E --> F[Coordinate with Other Trades]

This ensures safe, coordinated, and code-compliant floor design.

IS 2792: Strength and Stability - Key Points

1. Permissible Stresses in Transverse Bending (Clause 4.2.1)

• Permissible stress ≤ 1/10 of ultimate transverse strength (per IS 1121-1957).
• Typical permissible stresses for stone slabs:

2. Joist Design (Clause 4.2.3)

• Joists act as beams supporting stone floors.
• Consider dead load (stone floor, concrete, finishing) + live loads (per IS 875-1964).
• Design standards for joists:

Summary Formula for Bending Stress:

[ \sigma = \frac{M}{Z} \leq \sigma_{perm} ]

• (M): Bending moment
• (Z): Section modulus
• (\sigma_{perm}): Permissible stress from table above

flowchart TD
    A[Stone Slab] --> B[Calculate Ultimate Strength (IS 1121)]
    B --> C[Permissible Stress = 1/10 Ultimate Strength]
    C --> D[Select Permissible Stress from Table]
    D --> E[Design Joists as Beams]
    E --> F[Apply Dead + Live Loads (IS 875)]
    F --> G[Design per Material IS Codes]

Note: Always refer to IS codes mentioned for detailed design procedures.

IS 2792 - Materials: Key Specifications & References

• Stone Types: Refer IS 1805-1961 for classification and descriptions of stones used in construction.

• Structural Timber: Must conform to IS 883-1961 for grading, quality, and design.

• Rolled Steel Sections: Shall comply with IS 226-1962 for dimensions and mechanical properties.

• Cement: Use Ordinary, Rapid-hardening, or Low Heat Portland Cement as per relevant IS standards (e.g., IS 269 for Ordinary Portland Cement).

• Aggregates: Coarse and fine aggregates must meet IS 383 (Second revision) for quality and grading.

• Storage & Handling: Follow IS provisions for each material to avoid damage—especially critical for stone slabs (Clause 7.1).

Summary Table of Relevant IS Codes for Materials

Important Notes:

• Always verify material compliance with the latest IS revisions.
• Proper storage and handling per IS ensure durability and structural integrity.

flowchart TD
    A[Materials] --> B[Stone (IS 1805)]
    A --> C[Timber (IS 883)]
    A --> D[Steel Sections (IS 226)]
    A --> E[Cement (IS 269)]
    A --> F[Aggregates (IS 383)]
    A --> G[Storage & Handling (IS guidelines)]

IS 2792 – Programming the Work: Key Points & Specifications

Clause 6.1: Completion of Preceding Work

• All supporting elements (walls, pillars, main beams) must be completed early.
• Surfaces should be level and well-cured before flooring starts.
• Cement concrete over stone slab flooring must follow IS 456 guidelines.

Clause 3.1: Design & Construction Information Needed

• Area dimensions to be covered.
• Type and condition of supporting structures.
• Levels of walls/supports for floor placement.
• Treatment at junctions with adjacent floors/walls.
• Provisions for floor slopes, services, and ceiling fixings.

Coordination (Clause 3.3)

• Ensure proper communication between floor layers and other trades to avoid conflicts.

Summary Table: Programming Work Checklist

This programming ensures quality, timely, and coordinated flooring work per IS 2792.

IS 2792: Preparatory Work - Key Points & Specifications

1. Completion of Preceding Work (Clause 6.1)

• All supporting elements (walls, pillars, main beams) must be completed early.
• Top surfaces of supports should be level and well-cured before flooring.
• Cement concrete used over stone slab flooring should comply with IS 456: 1964.

2. Marking of Levels (Clause 6.2)

• Precisely check and mark the bearing surface levels of joists to ensure proper alignment.

3. Programming the Work (Clause 3.1)

• Collect detailed info on:
  • Area dimensions.
  • Type and restrictions of supporting structures.
  • Levels for walls/supports to receive flooring.
  • Treatment at junctions (floors, walls).
  • Provisions for slopes, fixing services, ceilings.

4. Cement Concrete Mix (Ref: IS 456)

• Typical mix for flooring concrete: 1:2:4 (cement:sand:aggregate)
• Minimum cement content and water-cement ratio as per IS 456 for durability.

Summary Table: Preparatory Work Checklist

flowchart TD
    A[Start Preparatory Work] --> B[Complete Supporting Elements]
    B --> C[Ensure Level & Cure]
    C --> D[Mark Bearing Levels]
    D --> E[Prepare Cement Concrete (IS 456)]
    E --> F[Start Flooring Work]

This ensures a sound base for stone slab flooring installation as per IS 2792.

Fixing of Joists as per IS 2792

Key Specifications:

• Positioning: Joists fixed at designed spacing, spanning between supports (walls, beams) (Clause 8.1).
• Surface Treatment:
  • Steel Joists: One coat of primer before fixing (Clause 7.3).
  • Timber Joists: Portion embedded in masonry treated with two coats of hot boiled tar (IS:212-1961), exposed parts with one coat of primer (Clause 7.3).
• Level Marking: Bearing surface levels must be checked and marked before fixing (Clause 6.2).

Design Considerations:

• Joists are designed as beams supporting floor loads.
• Load to consider:
  • Dead load (floor finish, concrete, stone floor)
  • Live load (as per IS 875-1964)
• Design codes for materials:

  Material	IS Code
  Precast RCC beams	IS 456-1964, IS 1343-1960
  Steel beams	IS 800-1962
  Timber beams	IS 883-1961

Basic Design Formula for Joists (Beam Theory):

[ M_u = \frac{wL^2}{8} ]

• (M_u): Ultimate moment
• (w): Uniform load (dead + live)
• (L): Span length

flowchart LR
    A[Mark Levels] --> B[Apply Protective Treatment]
    B --> C[Fix Joists at Designed Spacing]
    C --> D[Check Alignment & Stability]

This ensures proper fixing, durability, and load transfer as per IS 2792.

Key Specifications & Formulas for Laying Stone Slabs (IS 2792):

• Bearing of slabs on joists:
  As per Clause 9.1 and 4.2 (refer IS 2792 for 4.2 details), ensure adequate bearing length on joists for stability.

• Joint filling:

  • Use cement-sand mortar (1:3 mix) of stiff consistency.
  • Mortar joints must be fully pressed and grouted.
  • Optionally, add 5% crude oil by weight of cement to mortar for better workability and durability.

• Stone slab preparation (Clause 7.2):

  • Edges must be chiseled square for uniform mortar joints.

• Thickness (Clause 5.8.2):

  • Minimum slab thickness = 3 cm or as per structural design.
  • Tolerances per IS 1127-1957.

Summary Table:

flowchart TD
    A[Stone Slabs] --> B[Placed over beams/joists]
    B --> C[Edges chiseled square]
    C --> D[Set in close rows]
    D --> E[Mortar joints filled (1:3 cement:sand)]
    E --> F[Optional: Mortar + 5% crude oil]
    F --> G[Top joints grouted]
    G --> H[Underside joints pointed or finished]

This ensures a level, durable, and well-bonded stone slab floor system per IS 2792.

IS 2792: Laying Concrete Layer Over Stone Slab — Key Points

1. Stone Slab Placement (Clause 9.1)

• Slabs placed over beams with bearing as per Clause 4.2.
• Slabs set close in rows; joints grouted with cement-sand mortar (1:3 mix).
• Mortar is stiff; pressed into joints.
• Optional: Add 5% crude oil by cement weight to mortar for better workability and waterproofing.
• Underside joints can be pointed or finished as specified.

2. Concrete Layer Over Stone Slab (Clause 10.1)

• After grouting, lay lime concrete layer for waterproofing.
• Mix options:
  • 1:1:2 (lime: sand: aggregate) for good waterproofing (e.g., roofs).
  • 1:1:3 where less exposure or additional waterproofing exists.
• Thickness: Not less than 7.5 cm after consolidation.
• Lay concrete to a level surface; consolidate by beating with wooden hand beaters.

3. Cement Concrete (Clause 5.10)

• Cement concrete over stone slabs must comply with IS 456: 2000 standards.

Summary Table: Lime Concrete Mix & Thickness

Additional Notes:

• Proper grouting and consolidation ensure durability and waterproofing.
• Use wooden beaters to avoid damaging the lime concrete surface.
• Crude oil additive improves mortar flexibility and water resistance.

flowchart TD
    A[Stone Slabs Laid on Beams] --> B[Grout Joints with Cement-Sand Mortar (1:3)]
    B --> C[Lime Concrete Layer Laid (1:1:2 or 1:1:3)]
    C --> D[Consolidate Lime Concrete (≥7.5 cm thick)]
    D --> E[Level Surface & Waterproofing Achieved]

This ensures a durable, waterproof concrete layer over stone slab flooring per IS 2792.

IS 2792 - Finishing of Stone Floor (Clause 11.1)

Key Specifications:

• Finishing Layer: Cement plaster of mix 1:3, thickness 20 mm is recommended over stone floors.
• Alternative finishes may be used as per relevant IS codes.

Suitable Finishes & Relevant IS Codes

Additional Notes:

• Supporting elements (walls, beams) must be completed and leveled before finishing.
• Thickness and mix ratio ensure durability and proper bonding.
• Refer to the respective IS codes for detailed installation procedures and quality control.

flowchart TD
    A[Stone Floor] --> B[Cement Plaster 1:3, 20mm]
    B --> C{Finish Type}
    C --> D[Cement Tiles (IS:1443)]
    C --> E[Terrazzo (IS:2114)]
    C --> F[Mud PHUSKA (IS:2115)]
    C --> G[Mastic Asphalt (IS:1196)]

Summary: Use 20 mm thick 1:3 cement plaster or other IS-specified finishes for stone floors, ensuring supporting structures are complete and level before application.