What is setting out? It is the process of developing the physical positions of corners and walls of a building, and it’s done by transferring dimensions from the layout plan to the ground.
Setting out is done when building a new house, or when renovating an already existing one, especially an extension. The process of Setting out is done by a contractor, and overseen by the lead project consultant engineer, architect or any other qualified member of the project team.
The main function of setting out is to establish the position of the trench and wall of the house as well as the position of corners and rooms.
It is during this stage that the position of the landscaping area, driveways and any other future proposal are taken into account; offsets are also established at this stage. Local authority by laws are also taken into account, especially regarding the position of the sewer and electrical lines.
METHODS OF SETTING OUT
1. Peg or rope method (commonly used).
2. Dumpy Level (Best for big construction projects)
For now, we will concentrate on the peg/rope method, best suited for small and medium constructions.
ITEMS REQUIRED IN SETTING OUT.
- Timber, 75mm by 50mm or any appropriate size.
- Nylon threads (Manila rope).
- Ordinary nails inch and 2 inch.
- Round poles to act as pegs or steel for hard ground.
- White chalk or lime.
- Clear hose pipe for determining horizontal levels.
- Sledge hammer.
PROCESS OF SETTING OUT A HOUSE.
After clearing the site by removing loose or vegetable soil, first establish a reference point or reference line. This is a point where you position the first peg (first corner of the house), which helps to ensure balance. One side of the house should run parallel to the boundary of the plot or an existing building.
Setting out is done on the principal of whole to part. According to this principle the largest possible rectangle of the building is found and set out. The rectangle is further partitioned into small parts (internal rooms).It’s very important to ensure that the big rectangle (external wall) is set in a horizontal level.
The level is obtained by use of a clear hose pipe filled with water. Ensuring that the pegs are positioned at the same horizontal level is very important as it eliminates arithmetic errors, which could arise when getting your diagonals, to establish if the house is indeed square.
The main rectangle is set using the pegs that are in horizontal level. The first rectangle is then divided into smaller parts (rooms).For this division of the internal wall to take place, profiles must be in place on the ground. Profiles consist of pegs, driven into the ground, with cross pieces of timber attached to them.
Although profile boards are temporary, they contain a lot of important information on distance, with the points clearly marked on them showing the position of the walls and width of trench. These can be marked on the profile board using nails, and later transferred to the ground for excavation.
It’s very important for the profile to be placed firmly on the ground, and at a safe distance from the excavation area, so that they can be used when setting the wall on top of the ground slab.
Why is it important to get the square of a house?
Mistakes done when setting out can come back to haunt you. One of the classic mistakes is failing to get the square of the floor plan correct.
a) It has repercussions on the roofer. If the right-angled corners of a house are not positioned correctly, the roof cover and the rafter will not be of the same length, which also affects the uniformity of the roofing design.
b) Failing to position the right-angled corners correctly can also result in an uneven layout when finishing the floor, especially if you are using ceramic or granite tiles.
c.) Failing to get the correct dimensions and position of the right-angled corners can result in an uneven pattern when fixing the brandering and installing the ceiling boards or cover.
Its worth noting that although not all house designs are based on right-angled corners, all houses designs modeled on right-angled corners should follow the requisite design layout and procedure, failure to which would result in an aesthetically unappealing house.
GETTING THE SQUARE OF A HOUSE.
(i) Using the large mason’s square
The square refers to the right-angled corners of a house. A large square may be used to set out and mark off the positions of inside walls. This is commonly used and consumes less time. After setting the base line, the second line is used to determine 90 degrees from the base line.
Position one side of the large square on the base line, and make sure the second line is along the other side of the square. Repeat the same process on the other corners, and finally check for diagonals which must be equal.
(ii). The 3-4-5 method.
The first line to be set out is the base line, and the positions of all the other walls are measured and determined from this front line. If the building is rectangular, right angles are set off from the base line by using the 3-4-5 method.
The second line is set out on one of the sides of the rectangle. This line intersects the base line at the corner of the future building. To make sure that this corner is at right angle, we use the 3-4-5 method.
From the base line you mark out a triangle that has three sides measuring 3 X 4 X 5 units or their multiples. You will end up with a right-angled corner. Repeat this process on all sides of the house to ensure that all dimensions are correct.