What is the maximum allowed water absorption for roofing slate?

The maximum average water absorption should not exceed 0.6 percent by mass (Clause 4.2 & Table 2).

What are the standard thicknesses for slate tiles under this code?

The nominal thickness ranges from 4 mm to 6 mm, with a tolerance of ±1 mm (Table 1).

What is the minimum required strength for roofing slate?

The minimum average modulus of rupture, when tested in a wet condition, must be 60 MPa (Clause 4.4 & Table 2).

How is the durability or weather resistance of slate checked?

Through a sulphuric acid test where the increase in weight should not exceed 0.2 mg/cm² (Clause 4.3 & Table 2).

IS 6250

: 1981

Roofing Slate Tiles

CurrentSpecializedSpecificationMaterials Science · Stones

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This standard specifies the requirements for natural slate tiles intended for roofing. It covers material characteristics, dimensions, tolerances, physical properties like water absorption and strength, and the test methods to verify conformity.

Roofing Slate Tiles

Quick Reference Values

Maximum average water absorption0.6 percent

Minimum average modulus of rupture (wet)60 MPa

Maximum allowable increase in weight (Weathering Test)0.2 mg/cm²

Nominal thickness range4 to 6 mm

Thickness tolerance±1 mm

Practical Notes

This standard is crucial for heritage and conservation projects where slate roofing is common.

Slate is a natural, brittle material; proper handling, storage, and installation techniques are critical to avoid breakage.

The 'ring test' (tapping the slate to hear a clear sound) is a common on-site qualitative check for hidden cracks, though not a formal test in this standard.