Construction material cost has been steadily increasing over the years.
5 years ago, the average construction cost in Nairobi for a medium-priced building was KES 15,000 per square meter.
Currently, this cost has increased by 68% to an average of KES 22,000 per square meter for the same.
The trend does not seem to be slowing down any time soon.
Therefore, we need to think outside the box to keep costs low and still maintain the same or oven higher quality of construction.
This can be achieved by using ingenious methods of cost-cutting from the foundation stage through to the fines.
FOUNDATION
On average, foundation costs approximately 10% of the total cost of construction.
The main works in a foundation are:
1. Excavation
2. Reinforced concrete works [foundation footing and ground floor slab]
3. Masonry walling to ground floor level
Excavation costs can be reduced by use of machinery -Excavators. An excavator is rented at an average cost of KES 6000 per hour and would take 2 to 3 hours to excavate the foundation of a 3 bedroom house.This brings the cost to kes 6000 x3 = kes 18,000.
Excavating the same using manual labor would take an average of 7 days with 10 men at a cost of kes 300 each per day. This brings the cost to KES 300 X 10 X 7 = KES 21,000.
Reinforced concrete works
This consists of concrete reinforced with twisted steel.
A cubic meter of concrete on average takes 7 bags of cement and will cost a minimum of KES 8,000.
A cubic meter of masonry stone consists of 75 stones of 300mm long by 200mm wide. Each stone costs an average of KES 25. This estimates to approximately KES 25 X 75 = KES 1,875.
This is approximately 75% cheaper than concrete.
The reinforced concrete foundation footing can be replaced with masonry walling to achieve this great saving.
Ground Floor slab.
On average, a reinforced concrete ground floor slab costs KES 1,200 per square meter.
Masonry walled horizontally can replace this slab. A square meter of masonry walling using machine cut stones costs KES 40 X 15 Stones = kes 600. Add KES 100 for cement plaster and this brings it to KES 700 per square meter. This constitutes a savings of nearly 45%.
Old colonial homes built in the early 1900s in Kenya utilized these cost-cutting methods and are still standing to date.
A good example is the Officer's Mess at the National Youth Service Bahati Farm in Nyandarua.
The foundation footing and floor slab is made of masonry walling and it still stands to date, nearly 100 years from the day it was constructed.
With the passage of the new constitution, we hope that such a method of foundation construction will be allowed by the Local Authority. The current Building Code in Kenya specifics too much concrete / cement used because resulting in a high cost of foundation construction.
Conclusion.
With the use of Machinery for excavation [15% savings] and use of masonry to replace reinforced concrete on foundation footing [75% savings] and ground floor slab [45% savings], this will greatly save on the overall foundation construction costs.
Francis Gichuhi
http://www.a4architect.com