I guess you will need. Kajiado you need approvals that one am sure. To be save visit mavoko offices and enquire. Was the wall in the initial approved plan for the house, if yes then the approvals should have been granted together and hence you have nothing to worry about. If not then they demand for architectural drawings of the fence.

in Nanyuki when you present the Building plans for approval there is a charge for fencing to make the totals to 19k I used that to put a fence around and never got issues.