Pre-Construction Site Works (Lecture # 8)​ – PDF

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Pre-Construction Site Works (Lecture # 8) – Additional Video 1

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Pre-Construction Site Works (Lecture # 8) – Additional Video 2

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Pre-Construction Site Works (Lecture # 8) – Excerpt

• Pre-Construction Works
• Engr. Shad Muhammad
• Lecturer
• Department of Civil Engineering
• COMSATS University Islamabad, Sahiwal Campus.
• Pre-Construction Works
  Table of Content
• Construction of Foundation – Depth, Width, Layout and Excavation
• Depth of Foundation
• Width of Foundation / Footings
• Processes involved in Construction of Foundation
• Precautions while designing a Foundation
• Precautions during Excavation for Foundation
• Demarcation / Layout Procedure for Foundation
• Advantages of Layout with the help of marking pillars
• Disadvantages for doing the work without layout
• Materials & Tools used during Setting up of Layout
• Setting out Perpendicular Lines
• Timbering of Trenches
• Pre-Construction Works
  Construction of Foundation – Depth, Width, Layout and Excavation
• Pre-Construction Works
  Depth of Foundation
• Pre-Construction Works
  Width of Foundation / Footings
• Pre-Construction Works
  Processes involved in Construction of Foundation
• Pre-Construction Works
  Processes involved in Construction of Foundation
• Pre-Construction Works
  Processes involved in Construction of Foundation
• Pre-Construction Works
  Processes involved in Construction of Foundation
• Pre-Construction Works
  Processes involved in Construction of Foundation
• Pre-Construction Works
  Precautions while designing a Foundation
• Pre-Construction Works
  Ratio of Cement Concrete and Mortar for Foundation
• Pre-Construction Works
  Soil having Safe Bearing Capacity
• Pre-Construction Works
  Precautions during Excavation for Foundation
• Pre-Construction Works
  Precautions during Excavation for Foundation
• Pre-Construction Works
  Precautions during Excavation for Foundation
• Pre-Construction Works
  Demarcation / Layout Procedure for Foundation

1.For layout of a building baseline is marked on the ground either from center line of the road or from any permanent building nearby. This line helps to mark out the front of a building.

2.Side baseline is also marked with the help of side structure or road, or it can be marked with the help of first baseline or boundary of the plot.

3.Fix temporary pegs at the center line of walls/columns on both sides of walls and columns in front and back side.

4.Fix peg at the center line of walls/columns on both sides of wall and columns in left and right side of front of building.

• Pre-Construction Works
  Demarcation / Layout Procedure for Foundation

4.Check diagonals of the square or rectangle formed after fixing pegs.

5.Construct marking pillars with pegs at a distance of 1.5 meter to 2 meters and their top surface should be plastered.

6.Mark center line on the top of marking pillars with the help of thread (Soot) or with the Theodolite in big projects and the diagonal and other dimension should be checked.

• Pre-Construction Works
  Demarcation / Layout Procedure for Foundation

7.Level marking pillars on all corners of building and the top level is fixed at a proposed plinth level.

8.Mark the foundation of walls/columns according to drawing on the ground with the help of centerline marked on the marking pillars.

9.Mark foundation trenches on the ground with chalk powder.

• Pre-Construction Works
  Demarcation / Layout Procedure for Foundation
• Pre-Construction Works
  Advantages of Layout with the help of marking pillars
• Pre-Construction Works
  Disadvantages for doing the work without layout
• Pre-Construction Works
  Materials & Tools used during Setting up of Layout
• Pre-Construction Works
  Materials & Tools used during Setting up of Layout
• Pre-Construction Works
  Setting up Right Angles in Layout – 3-4-5 Method
• Pre-Construction Works
  Setting out Perpendicular Lines: The Rope Method
• Pre-Construction Works
  Setting out Perpendicular Lines: Optical Squares
• Pre-Construction Works
  (1) Site Survey

(1)  First of all site is surveyed and topographical details are drawn on the site plan. If the area is small, topographical details are drawn by metal chains but if it is large, then plane table and theodolite are used for this purpose.

(2) Contouring is done by any suitable method of contouring and the contours are drawn on the site plan.

(3) Following the contour map, site is leveled doing necessary cuttings and fillings with the help of any suitable machinery.

• Pre-Construction Works
  (1) Site Survey
• Pre-Construction Works
  (1) Site Survey

(4) The datum level is set out.

• It is a level marked on the sections of the drawings, from which all heights and depths are marked in figures.
• This level is marked by the architect.
• The datum is usually taken as the surface of the finished ground floor, abbreviated on the working drawing as F.F.L.
• It is set out by a leveling instrument.
• A peg is driven into the ground such that its top is at the F.F.L.
• Pre-Construction Works
  (1) Site Survey

(5) The ground floor plan is marked on the ground.

• First of all center lines of all walls are marked on the ground.
• Right angles are taken by cross staff, optical square or more precisely, by a Theodolite.
• The lines showing the intended lines of foundation trenches are marked by driving wooden pegs along these lines.
• Pre-Construction Works
  (2) Profile Boards
• These are horizontal wooden boards fixed on edge at the datum level, outside the foundation dig for a building.
•  
• The level at which these are fixed is usually basement or ground floor or a convenient no. of feet, above or below it.
• Pre-Construction Works
  (2) Profile Boards
• Pre-Construction Works
  (2) Profile Boards
• Nails or saw cuts in the top edge of these boards show the dig lines, footing lines, walls lines and other building lines, for setting out the lower part of the building.
• One profile board is set at end of each line, i.e., two for each corner, so that strings can be stretched between the nails to show any required line at any time.
•  
• Bricks are then laid in the foundation by plumb bob from the extended strings.
• Pre-Construction Works
  (2) Profile Boards
• Pre-Construction Works
  (3) Removal of Top Soil
• Before the foundation trenches are excavated, the surface vegetation, roots, plants, shrubs and usually all the top soil up to a depth of 150 mm to 300 mm will have to be removed, from the area of the site to be covered by the building.
•  
• This is done to ensure that the ground, upon which the structure is to be built, will be sterile (free from decomposable material i.e., organic material).
•  
• The removed top soil is valuable for subsequent use in the garden lay-out.
• Pre-Construction Works
  (4) Site Drainage
• The building regulations also require that sub-soil of any site to be used for building must be effectively drained.
• If the natural drainage of surface water through the ground is not sufficient, a line of agricultural drain pipes (porous pipes) can be laid on the uphill side of the site to intercept ground water that would, otherwise, flow towards building.
• Pre-Construction Works
  (5) Excavation
• When the setting out is completed and the profiles are in position, excavation of the trenches for the foundation is started.
•  
• The width of the trench is read off from the profiles and the depth of the trench depends upon finding a suitable sub-soil to give a firm bearing capacity (according to design).
•  
• The foundation concrete must also be below the depth at which it will not be affected by seasonal movement of the sub-soil (according to design).
•  
• It is now common practice to use earth moving machines for excavations on all contracts except on isolated small sites.
• Pre-Construction Works
  (5) Excavation
• Machines, which are in most common use are Hydraulic Diggers for excavation trenches, a Tractor Shovel for reducing levels by excavation and a Dumper for transporting soil from the site.
•  
• When soil has been tipped by the Digger, it can be lifted by the Tractor Shovel and put into the Dumper, to be carried away and discharged, where ever it is required for making up levels on the site.
•  
• Soil, which is used in this way for filling must be placed in layers, well compacted and allowed to settle for many months, so that it will not subside later, if built upon.
• Pre-Construction Works
  (6) Safety in Excavation
• Accidents in excavation are frequent and wp-wp-includess a high proportion of causalities.
• One cubic meter of soil weighs more than a ton and falling through only a short distance, even a half cubic meter of soil is sufficient to crush and kill a workman.
• Great care should be taken to support the excavation, adequately
• This is done by “Timbering of Trenches”, which is the process of supporting the sides of trenches by means of some wooden or steel members. The timbering is extended to the full depth of the trenches.
• Pre-Construction Works
  Timbering of Trenches
• Pre-Construction Works
  Timbering of Trenches
• Pre-Construction Works
  Timbering of Trenches
• Pre-Construction Works
  Timbering of Trenches
• Pre-Construction Works
  (i) Poling Boards

The various members used in timbering are:-

(i) Poling Boards

• The members placed vertically on the sides of trenches directly or after providing sheeting are known as Poling boards.
• The size of poling boards may vary from 1.75 cm x 32 cm.  to 22.5 cm.  x  4 cm.
•  
• Pre-Construction Works
  (ii) Waling, Wales, or Planks
• The members placed horizontally on sides of the trenches or against Poling boards are known as Waling, Wales or Planks.
•  
• The various sizes of Waling are 10 x 7.5, 10 x 10, 15 x 15, 17.5 x 5, 22.5 x 5, 22.5 x 7.5 cm.
•  
• Their length may vary from 2.5 to 4.5 m.
• Pre-Construction Works
  (iii) Struts
• The horizontal members of timber driven across the trenches between Poling boards or Waling are known as Struts.
•  
• The Struts are driven at a minimum distance of 2 m centre to centre.
•  
• The Struts may be circular , having diameter 7.5 m to 12.5 cm. or square 7.5 cm. to 10 x 10 cm. in section.
• Pre-Construction Works
  (iii) Struts
• Pre-Construction Works
  (iii) Struts
• Pre-Construction Works
  (iii) Struts
• Pre-Construction Works
  (iii) Sheeting
• The members which are placed horizontally or vertically close to the sides of the trenches for supporting their sides are called Sheeting.
• The length of sheeting may vary from 2.5 to 4.5 m.
•  
• The horizontal sheeting is supported by Poling boards and the vertical sheeting by Waling.
• Pre-Construction Works
  (iii) Sheeting
• Pre-Construction Works
  (iii) Sheeting
• Pre-Construction Works
  (iii) Sheeting
• Pre-Construction Works
  (iv) Runners
• The members which are vertically placed behind the Walings instead of the Poling boards are called Runners.
•  
• The Runners are long planks about 7.5 cm. thick and 1.75 to 22.5 cm wide.
•  
• They are pointed at their lower end and sometimes provided with an iron shoe and iron cap.
• Pre-Construction Works
  (iv) Runners
• Thank-you for Listening!

Be careful what you are asking for!

 (Shad)

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