Setting Out Building Procedures | Setting Out of Building Foundation
Setting out procedure is done in order to clearly define the outline of the excavation and the centre line of the walls so that construction can be carried out exactly according to the plan. The centre line method of setting out is generally preferred and adopted.
Setting out can be a very complex engineering process but with vast experience, it is quite easy. Experienced engineers and surveyors are those involved in setting out of structures, in large projects, services of land surveyors are required for more accurate transfer of levels and angles in setting out with the aid of a Theodolite to decided point around the building area
Setting Out Methods
- Setting out using pegging
- Setting out using blocks.
Here, we discuss setting out using pegging
Setting out Steps
- Site clearance
- Obtain the architect or building plan
- Get the necessary materials ready (i.e. pegs, nails, rope or line, hammer, tape, marking tool etc)
- Firstly, take note of the four corners where we have the proposed columns/pillars or as the case might be.
- Establishing the four corners in relation to the dimension of the building floor plan by pegging it
- After establishing these four corners insert nails at the centre- top of each peg and then run rope round the 4 pegs.
- Taking just one side measure the setback from the back of the fence to the end of building lines in that particular angle, then come to the front and measure the setback also as given on your drawing plan.
- After this go back to the rear or you may use the front as a point mark depending on which setback is more important to you. Measure the setback from the fence establish these two points with pegs then put a rope to cross both pegs and make them form a right angle or 90 degrees. To determine if your rope is at the right angle put a checker popularly called ‘square’ by bricklayers, this will direct you if you need to shift the other rope that can be varied since one is already fixed to form a base mark (i.e. the rope running through two pegs from the rear to the front either on the left side or the right side.
- After establishing a right angle, do your measurement to correspond with what is on the plan and then use the square at the other end to now establish the other two points. When establishing these points be conscious to place your peg at 1m or 3 ½ ft behind your building line i.e. where blocks will actually pass through.
- After this, nails peg at 3m interval round under the rope marking your building line, then nail tie rods (flat thin wood) on top round the entire area.
- Establish each room measurement by nails ( you require four nails at each measurement, two to establish the two sides of block you are going ) to place later on then the other two at both ends to serve as the points where you will excavate,the length of this is usually three times the width of the block you are using that is if you are using a 9“ block then expect to excavate or dig a trench of 27” wide.
- From the plan details, the width of excavation to be done is also marked by a line with pegs at appropriate positions. However, the excavation width is then marked by lime or by furrow with a spade.
- The digging or excavated depth depends on the type of foundation as recommended by your structural engineer.
- Next is casting of concrete bed/base
- After casting of foundation, use the nails on your profile board to determine where your blocks will follow Set blocks, 3-4 or more courses and partitions in reference to site topography
- Filling and backfilling of the trenches and inside trenches
- Casting your ground floor slab
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