Why construction joints are not provided in residential buildings?

A construction joint is provided when concrete pouring needs to be stopped due to some reasons and then is continued again later but in residential buildings, it is not required. Construction joints are often at the ends of the beams, slabs, tie beams,etc. in such cases, for the purpose of future extension. So, it is not provided in residential buildings.

Construction joint

various types of joints in construction are listed below;

Construction joint Expansion joint Contraction joint Isolation joint

Joints are used at:

Concrete slab Pavements

The purpose behind the use of joint :

To prevent the development of cracks in concrete

The reason behind not usage of construction joint in the residential building :

Especially construction joint is used in the concrete slab Construction joints should be designed in order to allow of displacement between both sides of the slab. Simultaneously construction joint has to transfer flexible stresses produced in the slab by external loads.

Construction joints are provided

1. When the day’s work comes to an end
2. When there hasn’t been enough fresh concrete
3. When the concrete member is tall, i.e, IS 456 restricts the free fall of concrete to 1.2 m. This means that if a column is concreted, the form works are placed only to a height of 1.2m so that the free fall of concrete does not increase 1.2 m. Further extending of the form works after the concrete has been poured is a tedious process.

Construction joints should be avoided whenever possible. Monolithically cast sections perform better than sections with joints.

The reason why we don’t see construction joints in typical residential buildings is because

1. The slab is mostly cast in a single day
2. The lintel beams, beams are also mostly cast in a single day

Construction joints are found in columns, but they may not be prominent because of the workmanship. Columns are generally cast in stages to a height of 1.2 m each time. Between each session, bond is ensured by providing a rough surface on the older section. This ensures the bond between the new layer and the old layer.

Construction joint is provided at where construction could not be done within a day like we have a long span of the slab and we have simple concrete mixture at that time we cannot construct the whole slab within one day, so we provide construction joint at the end of the day, next day we start work from that construction joint.

Basically in the residential building we have 1200 square feet slab area per one unit, that means we can easily do a slab work within a one day, so we do not need construction joint