Raft Foundation are used for the commercial building where we can get high strength for any construction building. And this foundation we can design for those buildings, where the bearing capacity is too low. if the bearing capacity of the soil is high so there we should not make a Raft foundation.
When Mat/Raft Foundation is Recommended
1- The bearing capacity of the soil is low.
2- Walls of the structure are so close that individual footings would overlap,
it is used for large loads.
3- Individual footings would cover more than half of the construction area.
Advantages of Raft Foundation
1- It requires little excavation.
2- It can cope with mixed or poor ground conditions.
3- It reduces differential settlement.
Disadvantages of Raft Foundation
1-Its takes much time from other foundations.
2- This foundation is too much expensive.
3- This foundation we can not make for a normal building.
4- We can not repair this foundation.
5- Mat foundation requires specific treatment for point loads.
6- Edge erosion occurs if not treated properly.