Wood suitable for making a suspended floor slab in Kenya is readily obtained from Mahogany, Pine or Cypress throughout the country.
Costs per linear foot.
Mahogany costs kes 200 per linear foot.
Cypress costs kes 66 per foot and Pine costs kes 60 per foot.
Mahogany is the best in terms of aesthetic appearance , longevity and strength , followed by Cypress then pine.
Pine wood tends to easily warp after some time hence mostly used for formwork which is temporary, around 30 days use.
Cypress doesn’t warp easily and can be used for external works such as roof trusses, fascia boards etc. It tends to grow dark and mouldy when sawn smoothly using wood smoothing machines.
Costs per m2.
From the above costs, Mahogany costs kes 1,400 per m2 of surface for a 2 inch thick surface. Pine costs kes 1,200 and Cypress costs kes 1,400 per m2 of a 2 inch thick slab.
The timber slab will need support costing around kes 300 per m2.
Labour and transport on average can cost 30% of material cost=30% x kes 1,400, assuming use of cypress, which is most commonly used .This comes to kes 420 per m2.
Total cost of a cypress slab will therefore be kes 420 + kes 300+ kes 1,400=kes 2,100.
A concrete slab costs around kes 2,600 per m2.
Concrete has superior qualities in that it is easy to clean, does not rot due to water/moisture, is long lasting, adds to structural strenthg of the house, reduces noice transmission, etc.
Therefore, most people investing in buildings especially for rent whereby they expect low maintenance will dig deeper into their pockets by 24% to use concrete slab instead of wood.
Uses in Kenya.
Notable wooden slabs in Kenya are KI restaurant in Parklands.
Trees help to remove excess carbon dioxide from the air, thereby making the air we breath fresher. Trees also give us the oxygen we breath.
The tree trunks are made of carbon obtained from the C02 gas in the air. Trunks are storage mechanisms of excess carbon in the atmosphere. When trees are cut, the earth finds it more complicated to remove excess C02, leading to greenhouse gas effect which leads to droughts. Also, when trees are cut, the earth lacks a mechanism to clean the air and produce oxygen, leading to more pulmonary diseases.
Therefore, alternative construction methods such as concrete which saves on use of trees should be encouraged.
Francis Gichuhi Kamau, Architect.