Site Preparation and Setting Out of Works | Setting out of building

The first work to be taken before the actual construction of a building is checking the dimensions of its boundaries as soon as the site is made available for construction. The vital boundary stones should be in their position and they should be checked with reference to the survey plan. Any difference that may be found regarding the front, rear or side dimensions should be reconciled before the work is started

Also Read: Municipal Requirements in Planning of Buildings | Building plan approval | Building Permit

 

SITE LAYOUT

The site layout for construction consists of the layouts of access roads, sheds, etc. They should be made as follows:

Access roads. An examination of the site drawing will determine the best layout for access roads. Wherever possible, access to the site for lorries and carts should be the shortest and capable of carrying materials either to a central place or various places of work, as may be desired.

 

Sheds. A study of the site drawing will indicate where weatherproof sheds must be erected for storage of materials such as cement, lime and other perishable materials. If the cement stores have to be large, they should be provided with two separate doors, one at each end one for accepting delivery and the other for the issue of materials.

 

SITE CLEARING

Site clearing means any one or all of the following works:

(i) Surface cleaning of grass, trees, anthills, hillocks, etc.

 

(ii) Cleaning of obstructions that may be above or below the ground level such as old foundations, old drainage works, old septic tanks, pit-type latrines and soak pits

 

(iii) Cleaning of obstructions belonging to other organizations such as drainage or water supply lines, underground electric or telephone cables

 

In the case of the first two items, they should be suitably removed and filled up to the ground level with good earth or sand. In the case of the third item, the concerned party should be notified well before the commencement of the work. If they are not to be disturbed during the construction, proper arrangements should be made for their protection.

 

ENCLOSING THE SITE

The building site is enclosed firstly for the safety of the public. If any person falls into an excavation made for the building without an enclosure, the supervisor will be put to blame, whereas if a person falls into an excavation in an enclosed area, that person is a trespasser. Secondly, by enclosing the site, it becomes more secure from any theft.

 

We should also ensure that the methods of storing materials are safe. For example, if the material is stored against a boundary wall, the wall should be strong enough not to fall down. If gates are provided, they should be wide enough and properly located for the lorry to come in. They should open inwards (not outwards) from the road.

 

WATER SUPPLY FOR CONSTRUCTION

Water is an important building material. If groundwater is available, it should be tested suitably for various uses. The cost of water comes to about one to two per cent of the cost of civil works. If no groundwater is available and water connection can be obtained from the municipal authorities, the pipes should be so laid that they will become part of the permanent water supply system after the completion of the building.

 

If suitable water has to be brought by lorries, temporary or permanent water storage tanks should be built for storing a sufficient quantity of water for each day and also for discharge from the supply tanker. If good groundwater is available, sinking a proper tube well (which can also be used later) at a suitable place will ensure a good supply of water during construction.

 

ELECTRICAL SUPPLY

Electricity supply is necessary for modern building works. The points to be observed are as follows:

1. Cables should be of good quality and suitably supported.

 

2. The switchboard, etc. must be properly enclosed and capable of being locked.

 

3. The switchboard should be about 1.5 m above the ground level.

 

PROTECTION OF EXISTING SERVICE LINES

Provision should be made to protect water, electricity, telephone and other public distribution lines which may be running through the property and be affected by foundation work.

 

We should mark all the existing service lines so that workers can identify them and can be careful not to disturb them during the construction. (There are many instances when underground electric lines have been disturbed, causing fire to nearby installations.) Sometimes, pipe ducts or concrete coverings are provided to protect these services if they cannot be removed from the site to other alternative places.

 

INITIAL CHECKS ON DRAWINGS

It is very important that before commencing actual setting out of the building on the ground,  the following checks should be made on the drawing from which the layout is to be carried out:

1. The sum of the intermediate dimensions should match with those of the overall dimensions.

 

2. The levels of various constructions (such as ground level with respect to road level, floor level, etc.) are clearly shown in the drawing.

 

3. Check whether the proposed building will actually fit into the plot with the mandatory distances specified by the municipal authority.

 

SETTING OUT OF BUILDINGS

Setting out of buildings consists of the following two operations:

1. The first operation is the setting out of centre lines. This means establishing the centres of the walls in case of a building with load-bearing walls, or the centre of columns in case of a framed building.

 

2. The second operation is the setting out of trenches or establishing the excavation lines for proceeding with the excavation.

 

We will separately describe the procedures used for the buildings with walls and for the framed buildings.

 

Must read: Various Steps In The Construction Of A Residential Building

 

Setting Out Centre Lines for Bearing Walls

The step-by-step procedure for setting out the centre lines of walls can be stated as follows (as shown in Fig. below):

 

Step 1: Establish a benchmark from which all levels for the various parts of the building can be established and which will not be disturbed during the building operations. This can be done by driving down a 50 mm x 50 mm angle 2 m long or a steel rod of suitable diameter and 2 m length in a previously dug hole so as to project about 10 cm from the ground level and then concreting the base to a suitable depth below the ground level to form a pedestal around it.

Setting out centre lines and checking out corners.

Step 2: The second step is to mark a baseline from which all dimensions can be measured. The centre line of the longest outer wall of the building is usually taken as the baseline. This is marked with respect to the boundary.

 

Step 3: The third step is to start from the baseline and mark the corner points of the centre line of walls of a building by means of 50 mm x 50 mm wooden posts driven firmly to the ground projecting 25 to 50 mm above the ground. A nail or saw cut is placed on the peg to indicate the exact centre point. Setting dimensions are measured with steel tapes and ranging roads between corner posts. It is essential that the 90-degree angles at corners are calculated using a builder's square or the 3: 4: 5 principle or a theodolite. Check whether all the dimensions of the diagonals tally.

 

Step 4: Using the corner points, transfer the centre line to the ground with dry lime by stretching lines between the pegs.

 

Setting Out of Trenches for Excavation of Bearing Walls

Having set up the centre line of corners and checked the dimensions of the building on the ground, we proceed to set out the lines for trenches using the centre line already established.

 

The aim of setting out trenches is to mark the direction and width of excavations to be carried out and also to mark the width of the wall to be built. This is carried out by using pegs or by profile boards.

 

These are masonry pillars or timber boards fixed to the ground some distance away from the exaction on which the excavation and wall boundaries can be marked as shown in Fig. below. These are set up at least 2 m clear of the excavation as shown in Fig. below. The profile boards may be masonry or timber.

 

The level of the top of the profile boards should be related to the side datum level and fixed at a convenient height if a boning rod (a traveller) is used to control the depth. The centre line, wall width and trench width are marked on the profile board. The trench width is marked on the ground by lime powder after stretching strings between the profile boards.

Setting out of trenches.

 

Setting Out a Framed Building

For setting out the foundation of a framed building also, we first establish the benchmark and set out the centre line of columns. This is usually carried out by a theodolite as the column centre lines are usually marked on a grid as shown in Fig. 2.3—one axis is marked as 1, 2, 3, 4, etc. and the other as A, B, C, D, etc.

Setting out footings of framed buildings by theodolite (I to Ill positions of theodolite).

 

In this case, we first fix all the peripheral points as shown in Fig. above. We first fix point 4 with respect to the boundaries of the plot. Then we station a theodolite at point 4 and fix F4, E4 to B4. Turn 90° and fix A3 to A 1. Secondly, fix theodolite at A 1 and fix B1 to Fl. Thirdly, station theodolite at F and fix F2 to F4 (check F4). The internal points can then be fixed easily by a theodolite or with stretched lines. Once the grid has been set out, profile boards can be fixed clear of excavation work to carry the excavation of the footings.

 

METHODS TO DETERMINE DEPTH OF EXCAVATION

For the construction of foundations and sewer drains, the depth of the base of the excavation is usually set out by means of sight rails and boning rods (also called traveller) as shown in Fig. below. In foundation, construction the base is to be levelled and for drain construction, it is to be laid to the required gradient. This operation is fully dealt with in surveying.

 

Another method that can be used for levelling of the foundation is the use of a water level. A plastic tube is filled with water and is used as a water level. First, the required depth of excavation is excavated in one place. In all the other sites, the level is determined by means of the water level with reference to this point. One more method is the use of the traditional levelling staff.

Determination of depth of excavation by boning rod or traveller and profile boards: 1. Strip foundation, 2. Column footing.

CONCLUSION: The procedure of site preparation and setting out of works is an important item of work as the final dimensions of the building and the sizes of various rooms depend on this operation. It should be carried out with precision by an experienced person.

 

Must read: How To Control Cost In Home Construction

FAQ

What is the 3 4 5 triangle method in setting up a building?

To get a complete square corner, we need to aim for a measurement ratio of 3: 4: 5. In other words, our straight line should be three feet long, and our vertical four feet long should be perpendicular, and our cross five feet long. If all three measurements are correct, we will get a complete square corner. We can also use multiples of 3:4:5 like 6:8:10 or 9:12:15

 

What is meant by setting out of buildings?

Setting out of buildings consists of the following two operations:

The first operation is the setting out of centre lines. This means establishing the centres of the walls in case of a building with load-bearing walls, or the centre of columns in case of a framed building.The second operation is the setting out of trenches or establishing the excavation lines for proceeding with the excavation.

 

What is setting out a plan drawing?

"Setting out" is the process of finding points for columns, site boundary level, pile level and other required structural areas according to the construction diagram.