What is the ideal soil for making mud mortar?

Soil with a liquid limit under 40% and a plasticity index between 9 and 18%. The combined silt and clay content should be over 50% (Table 1).

How long should the mud mortar mix be left before using it?

The soil-water mix should be allowed to soak or mature for at least 24 to 48 hours to improve its plasticity and workability (Clause 5.2).

What is the main limitation of mud mortar?

Its low strength and poor resistance to water. It is not recommended for structures exposed to heavy rain, flooding, or for buildings more than two storeys high (Clause 1.2).

How can mud masonry walls be protected?

Through measures like a damp-proof course, wide roof overhangs, and applying a protective plaster on the external face (Clause 7).

IS 13077

: 1991

Guide for preparation and use of mud mortar in masonry

CurrentSpecializedGuidelinesMaterials Science · Building Construction Practices incl. Painting, Varnishing

Download PDF BIS Portal Google

This standard serves as a guide for selecting suitable soils and preparing mud mortar for use in masonry. It outlines the process from material selection, preparation, and application to the protection of finished mud masonry walls, primarily for low-cost and rural construction.

Guide for preparation and use of mud mortar in masonry

Quick Reference Values

Recommended liquid limit of soil< 40%

Recommended plasticity index of soil9% to 18%

Maximum coarse sand content in soil< 30%

Minimum combined silt and clay content> 50%

Mortar soaking/maturing period24 to 48 hours

Typical compressive strength of mud mortar cubes0.2 to 0.5 N/mm²

Practical Notes

The quality of mud mortar is highly dependent on local soil properties; always test soil as per the IS 2720 series before large-scale use.

Protecting mud masonry from rain is critical for its durability. Ensure a good roof overhang and consider applying a stabilized mud plaster or lime plaster externally.

Adding stabilizers like chopped straw, rice husk, or cow dung can significantly improve workability and reduce shrinkage cracking in the mortar.