The cost of building material has been steadily increasing over the years.

5 years ago, the average construction cost in Nairobi for a mid-priced building was KES 15,000 per square metre.

Currently, this cost has risen by 68% to an average of KES 22,000 per square meter for the same.

The trend does not appear to be abating anytime soon.

So we need to think outside the box to keep costs down and still maintain the same or better build quality.

This can be achieved by using ingenious cost reduction methods from the foundation stage to finishing.

BASE

On average, foundations cost approximately 10% of the total construction cost.

The main works in a foundation are:

1. Excavation

2. Reinforced concrete works [foundation footing and ground floor slab]

3. Masonry walls up to the ground floor level

Excavation costs can be reduced by using machinery -Excavators. An excavator is hired at an average cost of KES 6,000 per hour and it would take 2-3 hours to dig the foundation of a 3-bedroom house. This brings the cost to kes 6000 x3 = kes 18,000.

Excavating the same using labor would take an average of 7 days with 10 men at a cost of 300 kes 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 requires on average 7 bags of cement and will cost a minimum of KES 8,000.

A cubic meter of masonry stone consists of 75 stones 300 mm long by 200 mm wide. Each stone costs an average of KES 25. This is estimated to be approximately KES 25 X 75 = KES 1,875.

This is about 75% cheaper than concrete.

The reinforced concrete foundation base can be replaced with masonry walls to achieve this great saving.

Ground Floor Slab.

On average, a reinforced concrete ground floor slab costs KES 1,200 per square meter.

Horizontally laid masonry walls can replace this slab. A square meter of masonry wall with 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 saving of almost 45%.

Old colonial houses built in the early 20th century in Kenya used these cost-cutting methods and still stand to this day.

A good example is the Officers’ Mess at the Bahati Farm of the National Youth Service in Nyandarua.

The foundation and floor slab are made of masonry walls and are still standing, almost 100 years after the day it was built.

With the approval of the new constitution, we hope that the local authority will allow this method of building foundations. The current Building Code in Kenya specifies that too much concrete/cement is used, resulting in high cost of foundation construction.

Conclusion.

With the use of excavation machinery [15% savings] and use of masonry to replace reinforced concrete at the foundation base [75% savings] and ground floor slab [45% savings]this will save a lot on overall foundation construction costs.

Francisco Gichuhi

http://www.a4architect.com