Setting out of a Building

S.K.A.K.D Samaraweera 150347

CE2006 Assignment 02

a. Understand the concepts of setting out of a building. b. Setting out the foundation of a building on the ground using given instruments.

Whole to part – setting out was done based on the principle of “whole to part

“ in order to that errors and mistakes of one portion do not affect the remaining

portion. Accordingly outline of the foundation trench was marked first and then the inner line of the foundation trench was marked.

Setting out is the process of transferring the distances, bearing, coordinates from a plan which was already prepared to the ground before the beginning of a construction. Plan was designed and prepared to give a correct position of setting out on the ground. Setting out also means the privation of marks, levels, profiles and other information which will enable other members of the construction team to carry out their works.

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At Viharamahadevi park in front of town hall, Colombo.

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Tape

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Poles

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Pegs

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Hammer

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Marking tread

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11.8 m

0.9 cm

10 m 7 . 8 m

6m

According to the given plan (fig 01) It was required to mark the lines of foundation for a room size 10m x 6m with the trench of 0.9 on the ground. First a Suitable place for the purpose was selected. Next using the tape, the length of the line AB = 11.8 m was measured and two pegs were placed at the points A and B. As the angle BAD is a right angle to mark the right angle at A method of 3,4,5 was used.

Fig 02

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3,4,5 method ,

This is a method used in surveying to mark a right angle when there is only tape and poles. For the purpose three persons are needed. As shown in fig 02 three persons are in three points of a triangle each person having the distance of 3m ,4m, 5m in between them. Then the angle at the person 1 (fig 02) will be a right angle.

After taking the right angle at the point the length of line AD (7.8m) was measured and a pig was placed at the point D. Similarly, the perpendicular AB(11.8m) length was measured. After that a pole was placed at point D and same as the point A with the use of 3,4,5 method, a right angle was set at D. Then the length DC (11.8 m) was measured using the tape. As the same way the right angle was set at the point C. Then the 0 mark of the tape was kept at the point C and measured the length towards B (C to B = 7.8 m). As the point B marked from C was coincided with the point B marked from A, we concluded that the setting out of outer line is correct. Finally, the diagonal of the outer line was measured and compared with the actual value 14.14m. As there was not much difference in the actual length and the measured length there we assumed that there was no error in the setting out of outer line.

For setting out the inner line, the “0” point of the tape was kept at point A and measured the distance of 0.9 (width of foundation) toward B and mark a point E on the AB line. From that mark a perpendicular EO to AB and marked the point O. To take the perpendicular line EO the 3,4,5 method was used. Mark F from the point B on the line AB and mark the BF = 0.9. similarly mark the FP = 0.9 perpendicular to AB. As the same way mark the points Q and R by setting out perpendicular KQ and LR to CD line for length of 0.9. Then the boundary of the inner line OPQR was marked.

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understanding the causes of errors and making conscious efforts towards eliminating them during construction is very important. some of the errors which might happen during the setting out are follows; 

Improper squaring - There can be measuring errors when taking right angles using 3,4,5 methods.

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Poor arrangement and positioning of pegs.

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Errors in lines and instruments used.

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Not holding the measuring tape parallel to the ground could make errors in the measurements.

This is a method of setting out of a building manually by using tape and other basic instruments when there is no instrument like digital theodolite or total station. If we read the markings of the measuring tapes wrongly at some point, that error transferring to the other parts of the building area and if you make multiple errors, thereby it makes a mess of the whole process. It is important to check for squareness of the area that is being set-out a by taking diagonal measurements which should always tally with what obtains on the plan. That will help to point out measuring errors.

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Setting out of a Building

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