Base course / Base coat under flooring

• Sub base

The strength of floor is depends on the strength of sub base. On weak sub base if floor is laid than it will be settle down. The strength of floor depends on the characteristics of the soil under the floor and the bearing capacity of soil. The soil under floor should be compacted well, so that there should be no loose pockets left any where in the area.

• Base course/ base coat

The purpose of the base concrete is to provide a smooth level surface at ground level on which a floor finish can be laid. Base course is laid in two parts
i.e.

• 100 mm thick sand filling or stone filing. The sand should be clean and dry. Do not use silt or very fine sand mixed with rubbish. The use of sand is to keep out dampness and white ants. The sand should be free from clay, silt, sulphates, dirt and other harmful salts and organic impurities.
• 100 mm thick cement concrete 1;8;16 or cement concrete  1;6;12 or 1;4;8 as per requirement and strength of floor is laid. The thickness of   cement concrete may be raised from 100 mm to 150 mm for heavy duty floor. The use of various mixes in detail is given below.

Cement concrete1:6:12

Where cement concrete 1:6:12 ratio is used it means 1 part of cement 6 parts of sand and 12 parts of coarse aggregate. This ratio cement concrete is low in strength and is recommended for the following type of building and works:-

• Used in foundation of two or three story buildings.
• Used in foundation of abetments, piers and retaining walls.
• Used in foundation where bearing capacity of soil low is obtained.
• Used as basecoat under taxi tracks, pavement and cement concrete road.
• Used as base coat in floor of stream in bridges and culverts.
  
• Cement Concrete 1:4:8

Where cement concrete 1:4:8 ratio is used it means 1 part cement 4 parts of sand/fine aggregate and 8 parts of coarse aggregate. This ratio cement concrete has medium strength and is recommended for the following type of buildings and works:-

• Used in foundation of multi story buildings.
• Used in foundation where low bearing capacity of soil is obtained
• In buildings where there is more vibration due to heavy traffic or running of factory.
• Under foundation of RCC columns, stairs, raft, RCC walls.
• Where water table is high.
• At the places where less depth of foundation available due to site condition.
• Air strips and taxi tracks base coat.