Site work & setting out

Part I – Substructure

When a builder is in possession of a building site he will have been provide with a site lay-out plan and the necessary drawings for him to erect the building.
Under most forms of building contract, it is the builder`s responsibility to see that the setting out is accurate these operations can be grouped under three headings.
1. Clearing the site
2. Setting out the building
3. Establishing a datum level

Clearing the site

May involve demolition of existing buildings, grubbing out of bushes and trees and the removal of soils to reduce levels. Demolition is a skilled occupation and should only be tackled by a skilled demolition contractor. The removal of tress can be carried out by manual or mechanical means, the removal of larges tress should be left to experts.

Building regulation C1 ‘The ground to be covered by the building shall be reasonably free from vegetable matter,’ this is in effect to sterilize the ground since the top 300 mm or so will contain plant life and decaying vegetation.
This means the top soul is easily compressed and would be unsuitable for foundations. Top soil is valuable as a top dressing for gardens and mat be disposed of in this manner. The method chosen for carrying out the site clearing work is determined by overall economics.

Setting out the site.

First task is to establish a base line from which the whole of the building can be set out. The position of this must be clearly marked on-site so that it can be re-established t any time. A steel ape (30metres would be a suitable length) for on-site measuring. Linen ad plastic coated tapes are also available – disadvantage of line tapes is that they are liable to stretch.

After the baseline has been set out, marked and checked the main lines of the building can be set out, each corner being marked with a stout peg. A check for setting out lines for right angles and correct lengths should then be made.
Profile boards clear of the foundation trench positions to locate the trench, foundations and walls are then set up.
These are required at all trenches and wall intersections

Establishing a datum level.

It sis key that all levels in a building are taken from a fixed point called “datum.” This point should be related to an ordnance bench-mark as it is established.
Ordnance bench mark – an arrow with a horizontal bench mark above the arrow, the centre line of the horizontal being the actual level indicated on an ordnance survey map. Bench marks are found cut or let into the sides of walls and buildings.
Where there are no bench-marks on or near the site a suitable permanent datum must be established, a site datum or temporary bench-mark could be a post set in concrete or a concrete plinth set up on site.

Establishing a datum level.

It sis key that all levels in a building are taken from a fixed point called “datum.” This point should be related to an ordnance bench-mark as it is established.
Ordnance bench mark – an arrow with a horizontal bench mark above the arrow, the centre line of the horizontal being the actual level indicated on an ordnance survey map. Bench marks are found cut or let into the sides of walls and buildings.
Where there are no bench-marks on or near the site a suitable permanent datum must be established, a site datum or temporary bench-mark could be a post set in concrete or a concrete plinth set up on sit.

SLOPING SITES

very few sites are level and therefore before any building work can be commenced the area covered by the building must be levelled. In building this operation is called reducing levels. Three methods can be used and it is the most economical that is usually employed.
1. Cut and fill: usual method because if properly carried out, the amount of cut will equal the amount of fill.
2. Cut: this has the advantage of giving undisturbed soil over the whole of the site but has the disadvantage of the cost of removing the soil from the site.
3. Fill: this is not to be recommended because if the building is sited on a filled area, either deep foundations would be needed or the risk of settlement t a larger state would have to be accepted.

HOARDINGS

This is a close boarded fence erected prior to the commencement of building operations if such
operations are adjacent to a public footpath or highway.

Functions of hoardings.

1. To provide protection for the public Resist impact damage
3. Resist anticipated wind pressures and adequately lit at night.
Before a hoarding can be erected a license or permit must be obtained from the local authority who will usually require 10 to 20 days’ notice. The license will set out the minimum local authority requirements for hoardings and define the time limit period of the license.

SITE STORAGE

prior to being used or fixed may require protection for security reasons or against the adverse effects which can be caused by exposure to the elements. Small and Valuable Items ~ these should be kept in a secure and lockable store. Similar items should be stored together in a rack or bin system and only issued against anauthorized requisition.
Large or Bulk Storage Items ~ for security protection these items can be stored within a lockable fenced compound. The form of fencing chosen may give visual security by being of an open nature but these are generally easier to climb than the close boarded type of fence which lacks the visual security property.

Typical Storage Compound Fencing ~ Close boarded fences can be constructed on the same methods used for hoardings.

Alternative Fence Types ~ woven wire fence, strained wire fence, cleft chestnut pale fence, wooden palisade fence, wooden post and rail fence and metal fences

Storage of Materials ~ this can be defined as the provision of adequate space, protection and control for building materials and components held on site during the construction process.

The allocation of an actual position on site will depend on: –

1. Space available after areas for units of accommodation have been allocated.
2. Access to facilities on site for delivery, vehicles.
3. Relationship of storage area(s) to activity area(s) – the distance between them needs
to be kept as short as possible to reduce transportation needs in terms of time and costs
to the minimum. Alternatively, storage areas and work areas need to be sited within the
reach of any static transport plant such as a tower crane.
4. Security needs to be considered in the context of site operations, vandalism and theft.
5. Stock holding policy – too little storage could result in delays in waiting for materials to
be delivered, too much storage can be expensive in terms of weather and security
protection requirements apart from the capital used to purchase the materials stored on
site.