The idea of building affordable permanent houses using local materials was borne out of challenge of housing deficit of about 150,000 units per year in 2003 when NARC came into power. We challenged ourselves as Kenyan Engineers to develop construction products using local materials that could ensure faster construction (efficient), reduce waste, durable and economical. That is how we invented HICU wall block, HICU hollow pots and developed HICU building Technology. We have obtained patent KE228 and several industrial designs IDN 743 for all the products under this technology. We have also obtained KEBS standard for all of our products.
The HICU wall blocks are concrete masonry units that interlock vertically hence eliminating the horizontal mortal joint in construction which limits construction of a walls to four courses in a day. With HICU Wall blocks you can construct walls of a building in a day without compromising the robustness of a building. HICU wall block saves on labour and reduces wastage. The size of each block is 200mm 0r 150mm wide by 200mm in height by 400mm in length.
HICU hollow pots are able to work as hollow pot and act as formwork spanning between the shutter formwork carrying the rib. It reduces the use of shutter form work by 2/3 (66%), by interlocking on the shutter formwork through an edge groove it ensures the rib width is uniform even during concreting unlike the ordinary hollow pots which keeps on shifting when concrete is vibrated ( the rib width is usually not uniform). The HICU Hollow pots reduces weight of slab by 25% and are less labour intensive since the spacing of bars is achieved when doing the formwork and the bent bars only needs to be dropped at the ribs and spacers added into them. The HICU hollow pot slab uses less concrete and less reinforcement bars.
HICU Hollow pots after placements of bars (Top and bottom) and before laying of mesh.
Building onto this innovation of HICU Hollow pots, it is possible to apply the same to the ground floor slab.
This would mean the ground floor slab would be suspended and would be carried by the beams which in turn transmit the load to the columns and column basis. This would be cost effective for small to medium structures especially in black cotton soils and in areas prone to flooding.
The present method of building substructure by excavating in cotton soil in mass, carting away to spoil the excavated materials and then filling the excavated area with hardcore besides constructing strip foundation and masonry footing is not only slow and tedious but costly and wasteful.
The ground is stripped of top soil (300mm) before excavating the column bases. The normal method of blinding, bar bending and placement of bars for column basis is followed before concreting. The same applies to columns, while the beam can be partially concreted (slab thickness part can be done with the slab) in order to allow for re-use of timber formwork.
Where the difference in level between the existing ground level and the bottom of the slab is big (in flood prone areas and crawling space is achieved) it is better to use timber formwork which can be removed once the slab is fully cured.
For the small difference of 200- 400mm (between excavated ground and bottom of slab) we recommend use of HICU Wall blocks to carry the HICU Hollow pot. Dust blinding is laid first before placing of blocks for leveling purposes. Incase, double courses of blocks are required (400mm difference) the first course is laid with small gaps between the blocks with the second course laid back to back. The Hollow pots span 340mm unsupported width which is open at the bottom which translates to 63% of cotton sub grade being unrestricted. The hollow blocks are about 20% voids at the bottom which is about 9% of the restricted balance of the cotton area. The total unrestricted area for cotton sub grade is 72% besides the HICU hollow blocks only serve as temporary support and once the slab sets it carries its own weight and other imposed loads.
The voids for the top HICU block can be filled at the top (or the top can blinded with concrete when in upside position) with small hardcore before laying the polyethylene paper and placement of HICU hollow pots.
The speed for laying the blocks is much faster than timber form work (the termites will not be a problem thereafter due to decaying timber) and they lock better and are very stable.
This is a great milestone since most of precast/prefabricated building still rely on traditional strip foundation and quarry masonry stone to build the substructure which is often slow, tedious and expensive. This means that the last existing barrier to automating house construction has been overcome.
This will lead to durable houses being constructed at a lower cost due to the efficiency realized from this technology.
We have used this Substructure construction for 12 no. Domestic servant quarter for our project in Kitengela and the savings in cost were enormous. The structural design for the substructure was done by a consulting Engineer.
We have attached cost comparison of HICU wall block to machine dressed stone, HICU hollow pot slab to solid slab and HICU suspended ground floor slab to traditional substructure for 1 no. domestic servant quarter.
We have paving blocks (cabro) from 50mm to 80mm for Quad and Unilock .