FORT JESUS, MOMBASA,KENYA: A CONSTRUCTION METHODOLOGY ANALYSIS
The Fort was built in the year 1593 A.D by the Portuguesse.
At the main entrance, you will notice the use of arcs at the wall openings[doors]. These were used to give structural support to the walls above.
Suspended floors were suported using steel I-Section beams.
The doors were made of hardwood and curved to a particular pattern. The doors were also decorated using iron.
The walls were made of coral stone . For structural stability, the walls were 600mm thick on the top and over 1 m thick on the bottom.This resulted to a tappering shape which aided in increased stabilty. The 600mm thick walls are also very stable due to the sheer thickness.
This thickness could enable them to open up small arched windows on the side facing the Indian Ocean where the cannons were fitted. The thickness also provided the required safety form invaders.
The average tradidional African wall was 1/8 times smaller since the Africans did not face similar security threats as faced by the Poertuguese. The wall was for privacy and insulation purposes only of which it fullfilled its purpose.
The fort was captured by the Omani Arabs in 1698.
This resulted in Islamic architecture elements addition such as pigeon holes at the top of the walls, and the house in the picture.
ARAB ARCHITECTURE
The Omani Arabs came in with new construction methods.
Their walls were much narrower and their suspended floors were supported using hardwood sections .These were spaced 300mm apart and coral stones placed on top.This was then plastered using clay to form the flat suspended floor surface.
For the door openings, hardwood planks were placed above.
The Portuguese had mastered the art of using the masonry arcs to form structural support as shown below.
LESSONS THAT CAN BE LEARNT.
Currently, to build a concrete suspended floor, we use concrete reinforced with steel bars. The Kenyan Bulding Code is to the British Standards. Once the conrete is poured into the formwork support, it hardens and the steel bars hold it together.
The Arabs used hardwood planks for the support and placed the stones on top with clay plaster in between.
A similarity with traditional indigenous African way of construction can be seen in the clay infill. The traditional Africans made their walls using Adobe clay infill similar to the one that the Arabs used for the suspended floor.
Since traditional Africans did not require to build vertically upwards[there was alot of land to build laterally], they did not develop this technology further.
Also, the traditional Africans did not have sophisticated enemies such as the Portuguese and Arabs hence they did not need to develop forts and other high-rise structures. Apart from the occasional raids by other tribes using bows, arrows and spears, there were no other enemies who would have nessesitated the change of construction methods to more secure structures.
Frank Gichuhi
Architect.
www.a4architect.com
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