What is the minimum compressive strength required for architectural granite?

100 N/mm² (approx. 1000 kg/cm²).

What is the standard tolerance for the thickness of a standard 18mm or 20mm granite slab?

The acceptable tolerance is ±1 mm.

IS 1136

: 1993

Granite Slabs and Tiles - Specification

CurrentFrequently UsedSpecificationMaterials Science · Flooring and Paving

This code specifies the requirements for dimensional tolerances, physical properties, and testing of natural granite slabs and tiles used for architectural flooring, facing, and skirting. Engineers and architects use it to establish quality benchmarks for procuring and accepting granite materials on site.

Specifies requirements for granite slabs and tiles used in construction, including aesthetic and physical properties.

Quick Reference Values

Minimum Specific Gravity2.6

Maximum Water Absorption0.5%

Minimum Compressive Strength100 N/mm²

Minimum Modulus of Rupture (Flexural Strength)15 N/mm²

Thickness Tolerance (up to 20mm)±1 mm

Practical Notes

Visual inspection is paramount; physical tests should only be performed on samples that pass initial visual checks for uniform color, grain size, and absence of cracks or veins.

When specifying granite for dry cladding on facades, particular attention must be paid to the Modulus of Rupture (min 15 N/mm²) to ensure structural integrity under wind loads.

Thickness variations beyond ±1 mm can cause significant issues in achieving a level finished surface, often leading to excessive mortar bed thickness during flooring.