The fact that the building didn't crumble down shows that it's okay chumas were done right and all, only problem is the foundations (he who builds his house on sand) In Kiambu and surrounding areas with red soil guys assume the ground is stable but with the rains and the numerous septic tanks, soak pits, boreholes and wells make it easier for the soil to become saturated, if the walls of a water tank caves in the process may cascade to the foundations and a house being heavily will cut through muddy red soil like butter.

SOLUTION
the guy has some options to save his house, underpin the house and build a 1.2 to 1.5 meter raft foundation which wold have been what they used in the first place that should cost him a cool 10-20 m.

very strange because to lay such a foundation for a huge building like that allot of digging all the sway down could have been done and sinkholes spotted before even before the foundation was put in place.as usual this is just shoddy workmanship

Do any human activities induce sinkholes?

Sure. Sometimes in karst areas [irregular landscapes formed when soluble rocks like limestone dissolve], when you drill a well—looking for water or for mining purposes—as you're pulling water out of the ground, you're lowering the groundwater table. That creates almost a toilet-flushing effect. You're lowering that groundwater level, and the soil that was sitting above just falls out. That's one way.

We also induce sinkholes when we start putting up parking lots and buildings and changing what we call the hydrologic regime. Instead of the water naturally soaking into the ground, it's now running off and being concentrated—being put into the ground at one point. (See "Guatemala Sinkholes Created by Humans, Not Nature.")

http://news.nationalgeog...xplainer-urban-science/

The fact that the building didn't crumble down shows that it's okay chumas were done right and all, only problem is the foundations (he who builds his house on sand) In Kiambu and surrounding areas with red soil guys assume the ground is stable but with the rains and the numerous septic tanks, soak pits, boreholes and wells make it easier for the soil to become saturated, if the walls of a water tank caves in the process may cascade to the foundations and a house being heavily will cut through muddy red soil like butter.

SOLUTION
the guy has some options to save his house, underpin the house and build a 1.2 to 1.5 meter raft foundation which wold have been what they used in the first place that should cost him a cool 10-20 m.