Roofing Slate Tiles

IS 6250: Scope - Key Specifications & Tables

1. Scope Summary

• Covers physical and dimensional requirements for slate tiles.
• Compliance based on rounded values per IS 2-1960.
• Applicable for sloped roof coverings.

2. Physical Properties (Table 1, Clause 4.1)

Note: Sulphuric acid test applies if specified by purchaser.

3. Dimensions and Tolerances (Clause 3.1)

4. Sampling & Conformity Criteria (Table 2, Clause 8.2)

5. Rounding Off

• Final values rounded

IS 6250: General Requirements for Slate Tiles (Clause 4.1 & related)

Key Physical Properties (Table 1)

Lot Acceptance Criteria (Clause 8.3 & 8.4)

• Tiles checked for general requirements, dimensions, workmanship.
• Defective tiles ≤ permissible limits (Table 2).
• Physical tests on groups of ≥ 25 tiles each.
• Lot passes if no tile fails any physical test.

Summary of Important Points:

• Water absorption controls durability against moisture.
• Modulus of rupture ensures mechanical strength.
• Softening depth limits surface degradation.
• Permeability test confirms waterproofing.
• Acid and weather resistance tests ensure longevity in polluted or harsh environments.

flowchart TD
    A[Slate Tile Lot] --> B[General Requirements Check]
    B --> C{Defective Tiles ≤ Limit?}
    C -- Yes --> D[Divide into Groups (≥25 Tiles)]
    D --> E[Physical Tests (Water Absorption, Strength, etc.)]
    E --> F{Any Tile Fail?}
    F -- No --> G[Lot Accepted]
    F -- Yes --> H[Lot Rejected]
    C -- No --> H

This ensures quality slate tiles conforming to IS 6250 for roofing applications.

IS 6250: Dimensions and Tolerances for Slate Tiles

Standard Dimensions (Clause 3.1)

Tolerances (Clause 3.2)

• Length and Breadth: ±5 mm allowed.
• Thickness: Minimum 15 mm (no tolerance specified, must meet or exceed).

Quality Control (Clause 8.3)

• Tiles must meet dimensions, tolerances, workmanship.
• Defective tiles per lot must not exceed permissible limits (see Table 2 in IS 6250).
• Non-conforming tiles are rejected.

Rounding Off (Clause 0.4)

• Use IS 2-1960 for rounding test results.
• Maintain significant figures consistent with specified values.

Summary

• Size: 600×300×15 mm or 500×250×15 mm.
• Tolerance: ±5 mm on length & breadth.
• Thickness: ≥15 mm.
• Defects: Limited as per standard lot acceptance criteria.

flowchart TD
    A[Slate Tiles] --> B[Dimensions]
    B --> C[Length & Breadth ±5 mm]
    B --> D[Thickness ≥15 mm]
    A --> E[Quality Check]
    E --> F[Dimensions & Tolerances]
    E --> G[Workmanship]
    F & G --> H[Defect Limits per Lot]

IS 6250: Physical Properties of Slate Tiles (Clause 4.1, Table 1)

*Sulphuric acid test applies only if purchaser requires (related to atmospheric pollution).

Additional Notes:

• Dimension Tolerance: ±5 mm on length and breadth (Clause 3.2).
• Sampling: Lots divided into groups ≥ 25 tiles for testing (Clause 8.4).
• Acceptance: No failures allowed in physical tests for lot acceptance.

Key Formula: Modulus of Rupture (MOR)

[ \text{MOR} = \frac{3PL}{2bd^2} ]

• P = breaking load (N)
• L = span length (mm)
• b = width of tile (mm)
• d = thickness of tile (mm)

flowchart TD
    A[Slate Tiles Lot] --> B{Divide into groups ≥ 25 tiles}
    B --> C[Perform Physical Tests per Table 1]
    C --> D{Any tile fails?}
    D -->|No| E[Lot Accepted]
    D -->|Yes| F[Lot Rejected]

This ensures slate tiles meet durability, strength, and weather resistance as per IS 6250.

IS 6250: Workmanship - Key Specifications & Sampling

Workmanship Requirements (Clause 8.3)

• Tiles must meet general requirements, dimensions & tolerances, and workmanship.
• Any tile failing any of these is defective.
• A lot is conforming if defective tiles ≤ permissible number (Table 2, col 3).

Sampling & Criteria (Clause 8.2, Table 2)

Physical Properties (Clause 4.1, Table 1)

• Water Absorption: Max 2% by mass average; variation ≤ 20% between samples.
• Modulus of Rupture: Min 60 N/mm² (dry), 40 N/mm² (wet).
• Depth of Softening: Max 0.05 mm.
• Permeability: No water oozing.
• Sulphuric Acid Immersion: No delamination, swelling, or flaking.
• Wetting & Drying: No delamination or splitting.

Testing Procedure (Clause 8.4)

• Divide lot into groups equal to the number of physical tests.
• Each group ≥ 25 tiles.
• All tiles tested must pass for the lot to be accepted.

flowchart TD
    A[Select Lot Size] --> B[Determine Sample Size & Permissible Defectives]
    B --> C[Randomly Select Tiles]
    C --> D{Check Workmanship, Dimensions, General Requirements}
    D -- Pass --> E[Divide into Groups for Physical Tests]
    D -- Fail --> F[Reject Lot]
    E --> G[Perform Physical

IS 6250 - Marking of Slate Tiles

Key Specifications for Marking (Clause 6.1 & 6.1.1)

• Each slate tile shall be marked with:
  • Manufacturer's identification mark or initial.
  • Optionally, the ISI Certification Mark (subject to ISI licensing rules).
• ISI Mark ensures compliance with the standard under ISI's inspection and quality control system.

Important Notes:

• The ISI Certification Mark use is governed by the Indian Standards Institution (Certification Marks) Act.
• Licensing details can be obtained from ISI.
• Marking ensures traceability and quality assurance.

Related Physical Properties (Table 1, Clause 4.1)

Rounding Off (Clause 0.4)

• Test results should be rounded per IS:2-1960.
• Maintain the same significant figures as specified values.

flowchart TD
    A[Slate Tile] --> B[Mark Manufacturer ID]
    A --> C[Mark ISI Certification (optional)]
    B --> D[Ensures Traceability]
    C --> E[Ensures Quality Assurance]
    D --> F[Compliance with IS 6250]
    E --> F

Summary: Mark each tile with manufacturer ID; ISI mark optional but regulated. Physical properties and testing ensure quality and durability per IS 6250.

IS 6250: Packaging - Key Specifications & Requirements

• Tolerance on Dimensions (Clause 3.2):
  ±5 mm allowed on length and breadth of tiles.

• Packing Arrangement (Clause 7.1):
  Tiles must be placed side by side along cleavage planes. Rows in packing boxes should be closely spaced to avoid damage.

• Physical Properties Reporting (Clause 5.1):
  Report average breaking load for both wet and dry tiles individually.

• Sampling & Conformity (Clause 8.4):

  • Divide lot into groups equal to the number of tests (see Table 2).
  • Each group: minimum 25 tiles.
  • All tiles tested must pass physical property tests (Table 1).
  • Lot passes if no tile fails any test.

Relevant Tables Summary

Packaging Arrangement Diagram

graph LR
A[Tiles placed side by side] --> B[Along cleavage planes]
B --> C[Rows closely spaced in box]
C --> D[Minimizes tile damage during transport]

Summary: Maintain ±5 mm tolerance, pack tiles tightly side by side, test physical properties on sample groups of 25, and ensure no failures for lot acceptance.

IS 6250: Sampling and Criteria for Conformity

Key Points from Clause 8.2 & Table 2

Procedure (Clause 8.3)

• Select sample size as per lot size (Table 2).
• Examine all sampled tiles for:
  • General requirements (Clause 2)
  • Dimensions and tolerances (Clause 3)
  • Workmanship (Clause 5)
• A tile failing any criterion = defective.
• Lot conforms if defective tiles ≤ permissible number (Table 2, col 3).

Additional Notes

• Rounding off test results per IS 2:1960 (Clause 0.4).
• Tiles should be packed side by side along cleavage planes (Clause 7.1).

flowchart TD
    A[Start: Lot of Tiles] --> B{Determine Lot Size}
    B -->|<= 10,000| C[Sample 30 Tiles]
    B -->|10,001-20,000| D[Sample 60 Tiles]
    B -->|20,001-30,000| E[Sample 90 Tiles]
    B -->|30,001-40,000| F[Sample 120 Tiles]
    B -->|40,001-50,000| G[Sample 150 Tiles]
    C --> H[Examine Tiles for Defects]
    D --> H
    E --> H
    F --> H
    G --> H
    H --> I{Defective Tiles ≤ Permissible?}
    I -->|Yes| J[Lot Conforms]
    I -->|No|

IS 6250: Water Absorption Test Key Points

Test Procedure (Clause 2.1, A-2.1)

• Dry tiles in oven at 105–110°C till constant mass.
• Cool and weigh dry specimen (mass = A).
• Immerse specimen fully in clean water at 27 ± 2°C for 24 hours.
• Remove, wipe surface water, weigh specimen within 3 minutes (mass = B).

Formula for Water Absorption (Clause 3.1, A-3.1)

[ \text{Percentage Water Absorption} = \frac{B - A}{A} \times 100 ]

Where:

• A = mass of dry specimen (g)
• B = mass after 24-hour water immersion (g)

Reporting (Clause 4.1, A-4.1)

• Test 6 tiles.
• Calculate average % water absorption of all 6.
• Report average as final water absorption.

Acceptance Criteria (Clause 8.4)

• Tiles grouped in lots of ≥ 25.
• No tile should fail physical tests including water absorption.

Summary Table

flowchart TD
  A[Dry tile at 105-110°C till constant mass] --> B[Cool and weigh (A)]
  B --> C[Immerse in water at 27±2°C for 24 hrs]
  C --> D[Remove, wipe, weigh within 3 mins (B)]
  D --> E[Calculate % Water Absorption = ((B - A)/A)*100]
  E --> F[Repeat for 6 tiles, report average]

This ensures accurate determination of water absorption per IS 6250.

Determination of Modulus of Rupture (IS 6250)

Key Formula (Clause B-4.1):

[ R = \frac{W \times L}{b \times d^2} ]

Where:

• R = Modulus of rupture (N/mm²)
• W = Breaking load (N)
• L = Span length between supports (mm)
• b = Width of specimen (mm)
• d = Thickness of specimen (mm)

Test Procedure (Clause B-3.1):

• Test 6 tiles: 3 soaked in water at 27 ± 2°C for 72 hours (wet condition), 3 in dry condition.
• Support tiles flatwise on bearers, load applied perpendicular to span.
• Use the tile testing machine as per Fig. 1 for flexural strength.

Reporting (Clause B-5.1):

• Report average breaking load separately for wet and dry tiles.
• Calculate modulus of rupture for each tile using the formula above.

Summary Table for Specimen Dimensions:

flowchart LR
    A[Prepare 6 Tiles] --> B[3 Wet (72 hrs soaking)]
    A --> C[3 Dry]
    B --> D[Place on supports]
    C --> D
    D --> E[Apply load perpendicular to span]
    E --> F[Record breaking load W]
    F --> G[Calculate R = (W*L)/(b*d²)]
    G --> H[Report average R for wet and dry]

This ensures consistent evaluation of flexural strength (modulus of rupture) of tiles per IS 6250.

IS 6250: Permeability Test for Slate Tiles (Appendix C)

Key Specification:

• No water shall ooze from the bottom of the tile during the permeability test (Clause 4.1, Appendix C).

Test Procedure Summary:

• Test Specimen: Slate tiles as per Clause 4.1.
• Water is applied on the tile surface.
• Observe any seepage or oozing from the underside.
• Report any seepage as failure.

Related Physical Properties (Table 1, Clause 4.1):

Important Notes:

• Tiles must be dry and wet tested individually.
• Permeability test ensures durability against water ingress.
• Failure to meet this indicates poor quality or potential durability issues.

flowchart TD
    A[Apply Water on Tile Surface] --> B{Water Oozing from Bottom?}
    B -- No --> C[Pass Permeability Test]
    B -- Yes --> D[Fail Permeability Test - Report Seepage]

This test ensures slate tiles are water-resistant and suitable for roofing applications.

IS 6250: Sulphuric Acid Immersion Test Summary

1. Test Solution Preparation

• Sulphuric Acid Solution (Sp. Gravity 1.145)
  • Mix 1 volume of concentrated H₂SO₄ (Sp. Gravity 1.84) with 7 volumes of distilled water (Clause D-2.1).

2. Test Conditions

• Temperature: 27 ± 2°C
• Duration: 10 days continuous immersion (Clause D-3.1)

3. Test Procedure

• Immerse test specimens fully in the prepared sulphuric acid solution for 10 days.
• After immersion, examine for any deterioration such as seepage, oozing, or surface damage (Clause 4.1).

4. Alternate Immersion Cycle (Optional/Additional)

• 16 cycles of:
  • 6 hours immersion in distilled water at 27 ± 2°C
  • 17 hours heating in air oven at 110 ± 2°C
  • Cooling to 27 ± 2°C (Clause E-3.1)
• Followed by specimen examination.

5. Acceptance Criteria

• No seepage or oozing through the bottom of the tile (Clause 4.1).
• Visual integrity maintained without significant surface degradation.

flowchart LR
    A[Prepare Sulphuric Acid Solution] --> B[Immerse Specimen at 27±2°C]
    B --> C{Duration 10 days}
    C --> D[Examine Specimen]
    D --> E{No seepage/ damage?}
    E -- Yes --> F[Pass Test]
    E -- No --> G[Fail Test]

    %% Optional Cycle
    B --> H[Alternate Immersion Cycle (16 cycles)]
    H --> I[Examine Specimen]
    I --> E

This test evaluates acid resistance of tiles/coatings against sulphuric acid attack per IS 6250.

IS 6250: Wetting and Drying Test Key Points

Test Procedure (Clause 2.1)

• Dry tiles at 105-110°C until constant mass.
• Cool and weigh (mass = A).
• Immerse in water at 27 ± 2°C for 24 hours.
• Remove, wipe surface water, weigh within 3 minutes (mass = B).

Calculation of Water Absorption (Clause 3.1)

[ \text{Percentage absorption} = \frac{B - A}{A} \times 100 ]

• A = dry mass of specimen
• B = wet mass after 24-hour immersion

Observations (Clause 4.1)

• Report any delamination, swelling, softening, flaking, or gas evolution during immersion.

Strength Test (Clause 5.1)

• Report average breaking load of both wet and dry tiles separately.

Summary Table: Wetting and Drying Test

flowchart TD
    A[Dry tile at 105-110°C] --> B[Cool and weigh (A)]
    B --> C[Immerse in water 27±2°C for 24 hrs]
    C --> D[Remove and wipe surface water]
    D --> E[Weigh within 3 minutes (B)]
    E --> F[Calculate % absorption]
    F --> G[Inspect for damage]
    G --> H[Perform breaking load test on wet and dry tiles]

This ensures tiles' durability against moisture cycles per IS 6250.