Building Technology
Post-construction strengthening
Hello everyone,

Recently I have observed some cracks developing in the walls of my friend's house. It seems to be happening because the load of the slab is being taken up by the walls.

Additionally, the slab was cast after the walls were raised, without leaving a 2 row gap between the slab and the walls. The walls are non load bearing structures, and overall it is a normal RCC beam column construction. Even the slab has sagged, and there is a considerable damage done to the clear cover.

Since it was constructed only 8 years ago, are there any methods through which the structure can be strengthened and protected from further damage?
Sriraj Gokarakonda
Post-construction strengthening
Sriraj, I am not clear on where the slab is located. Is this slab under the walls? or is the slab above the walls?

If the slab is under the walls, then movement (down) would be due to ground subsidence. Then the slab needs to be remounted upon more solid foundations.

If the slab is above the walls and is being held up by the walls and not by reinforced concrete vertical supports then you need to take the weight (load) of the slab off the walls by using more reinforced concrete supports.
Frank John Snelling
Post-construction strengthening
Dear Frank,

Thanks for your response.

The slab I was talking about is a roof slab. There are also vertical RCC columns, but even then the load is coming over the non-load bearing walls, which are normal earthen brick masonry.

It is not possible to provide more columns because they would disturb the flow in the house.

Aren't there any means by which it can be strengthened, like adding any extra feature to the existing structure other than entire new construction?
Sriraj Gokarakonda
Post-construction strengthening
Sriraj, Sorry, my mistake. I meant (but did not say) that the extra vertical support should be set in the walls.

If you cut vertical channels in the walls and put in reinforced concrete, Then the roof slab can be supported better and the compressive load causing cracks in the walls will be lessened.

Or, you could use Steel "I" beams, but I imagine that would be too costly.

You need to put in temporary supports while the work is being done, otherwise the walls may fail completely.

And, if you can raise the slab fractionally before putting in the extra supports, then this will relieve some of the pressure on the walls.

In Britain, temporary vertical supports for concrete slabs are known as "Acrow-Props" and function like car-jacks. Here in Turkey, a forest of wooden posts are used.

Footnote: These wall cracks may be caused in part by ground-subsidence, so you need to check the foundations. :)
Frank John Snelling
Post-construction strengthening
thank you very much :-)
Sriraj Gokarakonda


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