Eng. S. Gitonga
Structural Engineer
Eng. Gitonga leads structural design at TimberStone. Every foundation, slab, column and roof structure we build is designed and calculated by him, and the drawings that go to the county carry his stamp.
Background
Most of the structural work on this side of Mount Kenya comes down to one question: what is the ground going to do next. Around Laikipia you can move from good murram to black cotton soil inside a single plot, and a foundation designed for the wrong one of those is the most expensive mistake available to a homeowner. That is where the design effort goes.
Because TimberStone designs and builds, the drawings do not leave his desk and disappear. He sees the trial pits, he is on site when the foundation is set out, and he is the one who has to answer for it if a wall cracks in three years. That closes a loop that is normally left open, and it changes how a structure gets detailed. Nothing gets drawn that the team on site cannot actually build.
On our projects
- Foundation design based on the actual soil on your plot, not a standard detail
- Reinforced concrete design for slabs, columns, beams and retaining walls
- Structural calculations prepared for county submission
- Roof structure design in timber and steel
- Condition surveys on existing and stalled buildings
- Checking the work on site against the drawings
Written by Gitonga
Suspended slabs: solid, ribbed or precast
The first floor of a maisonette is the single most expensive structural element in the house, and there are three ways to build it. A solid slab is simplest and heaviest. A ribbed slab uses less concrete and reaches further. Precast is fastest and needs the least propping. Which one suits a house depends on the spans, the number of floors and how much timber for formwork the site can support, and the choice changes the cost of the columns and foundations below it as well.
10 min read
Reinforcement that survives the site
Reinforced concrete works because the steel is in exactly the right place. Move it, shorten it, or leave it too close to the surface and the element does not become slightly weaker, it can stop working the way it was designed to. Almost all of the reinforcement problems worth worrying about on a Kenyan house come down to six things, and all six are visible to anyone standing at the edge of the pour before the concrete goes in.
11 min read
Reading the cracks in a house
Most cracks in a Kenyan house are harmless. A small number are not, and the difference is usually readable from the crack itself. Direction, width, whether it tapers, where it starts and whether it passes through a structural element are what separate a plaster crack from a foundation problem. The most useful thing you can do with any crack is date it, measure it and watch it, because a crack that has stopped moving is a very different problem from one that has not.
10 min read
Concrete that actually reaches its strength
Concrete on a Kenyan site routinely reaches half the strength it was designed for, and almost always for the same reason: water added at the mixer to make it easier to place, then no curing. Neither costs anything to fix. Getting the water right and keeping the concrete wet for seven days is worth more than any change of cement brand or mix ratio.
12 min read
How to choose a foundation in Kenya
There are five foundation types in normal residential use in Kenya, and the choice between them is decided by six facts about your site rather than by preference or budget. Those facts are the soil, the depth to a stable stratum, the weight of the building, the slope, the water table and what is next door. Get them first and the foundation type usually chooses itself. Choose the foundation first and you are guessing.
11 min read
Building on black cotton soil in Kenya
Black cotton soil swells when it gets wet and shrinks when it dries, and it can move 50mm or more vertically through the seasons. It does not fail by settling under load, it fails by lifting unevenly, which is why houses on it crack in a pattern nobody expects. It is entirely buildable, but only if the foundation either sits below the layer that moves, or is stiff enough to ride over it, or is separated from it. Which of those three you choose depends on the depth of the soil and the weight of the building, and the only way to know that is to dig trial pits and test.
14 min read
Need this expertise on your project?
Tell us about the site or the building and we will come and look at it.