SETTING OUT OF A BUILDING PLAN ON GROUND

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.

                                                   3-4-5 method

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 14^th September 2016