‘Structural advice is vital for multi-storey buildings’

Annette Fisher

Annette Fisher

The recent collapse of a five storey building in Lekki with approximately 30 fatalities has prompted me to write on this very important issue regarding the structural integrity of buildings. Once a building is more than one storey in height (a bungalow) there must be a structural system in place to support one or more upper floors.

A single storey house simply uses load bearing walls to support a roof only; more than two storeys and above, then there are other options to use either a concrete frame or a steel frame system. Concrete frames are more commonly used in Nigeria. There is also another very critical aspect to taller buildings and that is they must also be built absolutely straight and should not be leaning to one side or another.

They must be plumb and in so doing this adds to the structural soundness of any structure. A leaning structure moves the centre of gravity of the building away from its stable true centre to either the left or right of centre; the further away the centre of gravity shifts from centre the more unstable that structure becomes.

Take for example a simple 30mm wooden stick say 1.5metres in length and stick into the ground; you will find that if it stands absolutely straight it is much stronger than when shoved into the ground at angle. If you left two sticks in the ground, one straight and the other leaning and left them for a day or two. The straight stick would still be there whilst the leaning stick would have dropped closer to the ground. Left longer than that it would eventually fall to the ground; and so it is with buildings.

The foundations of a building are also fundamental to its solidity. This is the base of the building that sits below the ground and upon which is laid the ground floor slab that we walk on within the living space of a house for example. Again the depth and size of your foundations need to be measured and calculated by a structural engineer to ensure that it will carry the dead and live loads of the building.

Live loads are people moving around and dead loads are the weight of the upper floors and all fixtures and fittings including the roof. Construct a multi storey building with properly measured structural beams and columns, that is erected plumb so that every floor sits exactly above the other no matter how many stories, and you will have a sustainable structural component that will stand the test of time.

You will need to employ the services of a qualified structural engineer to determine the loads required to build your house and calculate the required foundations and structural members needed to ensure that the building will stand and provide safe accommodation for the life of the building.

• Fisher is the Alternative Vice president, Europe, Common wealth Association of Architects.



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