Laying the foundation of a building is done after the survey of the plot has been completed. The survey beacons will show the physical boundaries of your property. The site to be covered by the building should then be cleared of tuft and vegetation matter. The contractor and Masons should then accurately determine corners of the foundation and use four short thick sticks that have been sharped on one side to physically mark each corner identified. Use the hammer to fix the sticks deeply into the ground in such a way that they should describe square at each of the corners of the building. Then determine the width of the trenches for the walls. Using this width the Mason strings two lines from one corner to the next, till the whole building is covered and in accordance with building drawings. The width between the lines should be slightly greater than the width of the wall of the proposed building. Using these lines as a guide ,the Masons and laborers should begin digging the foundation trenches. This should produce straight trenches that in turn will facilitate the mason to construct straight wall and in general building with accurate bearing and proportion. In short a structurally sound structure.Embed from Getty Images
Special care should be exercise to ensure the building is in the right place on the plot and that all load bearing walls have been identified and set out accurately on ground. Some of the tools used are measuring line and a square, in order to get the corners of the building right. The result is correct orientation of the proposed building with say the drive way, garage, stairs and balcony in right places
According to the Kenya building code of 1997 , “the foundation should designed and constructed in such manner as to sustain the dead load of the building imposed vertically and laterally and to transmit these loads to the ground in such manner that the pressure may not impair the stability of the building or adjoining structures. In addition foundation laying should also factor into the equation the effect of wind on the building. Also it should be taken down in such depth that will safeguard the building from swelling, shrinking or erosion of the subsoil.”
This entail digging the foundation trenches. The depth of the trenches will depend on the type of soil and slope of the construction site. Black cotton soil, clay, Alluvial, sand and red soil are considered weak and will require deeper trenches that go past its substrata. Also a sloping landscape will necessitate deeper foundation trenches to be dug out.
Good soils with hard surface that require standard or shallow depths for the trenches are Compact Murrum soil, Compact gravel, compact Magadi soil, brown shale, Coral, and Nairobi stone soil.
The point is that the foundation should rest on a solid base beneath the ground. Remember not to misuse the soil dug out because it can be used to fill the foundation base.
Depending on whether the building standard house or storey building ,the concrete is poured in the trenches up desired height.
For Storey buildings, the mason will install ribbed steel bar squares for all the corners of the building and then the concrete is poured and spread in and around them. Also the mason may lay Y 16 ribbed steel bars in the foundation trenches. All these is done to add strength to the foundation and enable it to hold together the base as one compact unit. Once this done, concrete is poured and spread in the trenches to desired height. Once the concrete has cured, lay the foundation stone and allow the masons the go ahead to build the foundation wall/stem wall.
Use soil to fill the foundation base before pouring in hard-core stones. This should then be covered by Murrum to create an even and smooth surface.
When the foundation is at the desired level and flat, prepare to pour a slab on it. To improve the durability of the building apply anti termite solution and anti –damp material to make the foundation water proof.
During pouring the slab , call in the plumber to install water and sewerage piping .Also an electrician can be called to install necessary electrical wiring conduits before the slab dries up.
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