Before starting a building construction engineers
have to set out the ground for defining clear breadth of excavation for
foundation and the center line of
the walls, which will help in carrying out the same house as it is designed on
its architectural plan. There are many methods used during the setting out,
some of them are the following: 3-4-5 method, the rope method and the single
prismatic square and the double prismatic square. The 3-4-5 method of setting
out is generally preferred and adopted, as it is the easiest among others.
Plan
view of the house
We are going to set out on the ground the
architectural plan view above, firstly the center line of the walls are
calculated. Then the center lines of the rooms are to be settled out by using
3:4:5 Method. With this method
we need firstly to set out a right angle from a certain point on the base line.
For us to set out right angles on
the field, we need a measuring tape, two ranging poles, pegs and three persons.
With this measuring tape, the first person have to hold on zero mark and on
twelve mark, the second person hold the
three mark between his/her thumb and index finger, and then the third person
holds the eight mark.
After all sides of the measuring tape
are stretched, we obtain a rectangular
triangle with lengths 3 m, 4 m and 5 m as it is indicated on the figure below,
hence the angle of the first person is a right angle. Which can allow us to use
multiples of 3 m, 4 m and 5 m. e.g. 6 m,
8 m and 10 m or 9 m, 12 m and 15 m. Etc.
The same process is to be repeated at every corner
of a building for you to obtain a right angle on each corner. And this is how
we set out a building on the field, using the 3-4-5 method!
After the setting out the excavation of foundation
have to be started and other construction works could proceed up to the roof
and final works of the building.
Picture of a house
after all its construction process
.
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By Didace BIZIYAREMYE on 14th
September 2016