@Osa
The architect is known as the chief consultant in the design process.
After you approve the final design (s)he will approach the other consultants you have mentioned (suppose to tender) on your behalf and get their input and cost. The total cost will be your design cost.
The architects commission is capped at 6% of the above cost.
There are also site visits to take into account which are usually an added cost if not included.
So for you to get a cost projection you will have to approach an architect first.
Average building cost KShs 15,000-25,000 per square metre (to be confirmed)
NB:
The design and construction costs are separate
'If you are not living on the edge,you are taking up too much space'
"We do not inherit the earth from our ancestors, we borrow it from our children" Native American Proverb