LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
SCAFFOLDING
It is a temporary structure used to have access to a place of work in order to perform
building operations.
A temporary structure that is constructed to support a number of working platforms at
different heights so as to enable workman to reach their work and permit raising of
materials
Scaffolding may include ladders, guard rails, working platforms and gangways
Scaffolds can also be used to support pars of a structure until they are self-supporting e.g.
during casting in situ concrete
Materials used on scaffolds
Tubular steel
Tubular aluminum alloy
Timber
Tubular steel – can be galvanised or plain tubes can be used and has the following advantages
The small diameter and standard length simplifies storage space
If overloaded metals don’t suddenly break like timber but give ample warning by
bending
Metals are adaptable to any purpose on construction site
It also undergoes very little deflation
Both welded and seamless steel tubes of 48mm outside diameter with a nominal
38mm bore diameter are recommended.
These can be obtained in galvanized form or special care will be taken after use such
as painting or oil bathing.
The main disadvantage being that it is susceptible to corrosion
Timber – members are tied together without use of couplers
Ends should be bound with galvanised hoop to prevent end split formation and care
should be taken in storage
If it is used, it should be of high structural qualities
Generally used as a temporary structuring scaffolding. The members are joined by a
wire or rope.
Scaffold Boards: Softwood timber is used and these form the platform to work on.
Softwoods of 225*38 section and not exceeding 4800mm in length should be used.
The ends should be bound by a 25mm by 0.9mmgalvanised hoop iron to avoid
splitting.
It suffers from dry rot
Aluminium alloys
3 times lighter than steel
Undergoes three times as much deflation as steel
Resistance to corrosion and there are more expensive.
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
These come in seamless tubes of 48mm outside diameter and no protective treatment
is required unless if they are to be used with wet cement or sea water. In that case a
coat on tubes with bitumistic paint is done before use.
u.d.l. of 6.7kN/m2 when supported at 1200mm centres.
NB – when metal tubes are used different types of scaffolds can be constructed such
as putlogs or builders scaffold, double or independent scaffold, truss – out or needle
scaffold
Scaffolds consists of following members and parts
SCAFFOLD FITTINGS
Major fittings used in metal scaffolding include:
Standards
These are vertical members that carry and transmit all load to the soleplate including
any operatives or materials on the platforms
They are horizontal members
Ledgers
These are horizontal members parallel to the face of the building in the direction of
the length of the scaffold
Are used for connecting the standards
They provide support for the transom
Transom – these are horizontal measures perpendicular to the ledge which are used for
connecting 2 rows of and also used for carrying platform boards
Putlog – these are for tying the scaffolds to the building so at to resist any inwards or
outwards movement
Similar transoms, but one end is fitted with a special pier
So that the end may be placed in a slot left in the construction
Usually there is a gap in the mortar joint
Base plate – it is a square metal plate welded to a short length of tube and fitted to the bottom
of the standard
Some types have adjusted screw jerks which can be used to overcome small
differences in level when erecting scaffold on uneven ground
Sole plate – it is timber, concrete or metal plate used to distribute the loads to a base plate
It prevent the base plate from resting directly on to a thin surface
Guard rail – it is an additional horizontal member parallel to the ledgers and provided to
working level as the safe guard for workers
Additional ledger connected between standards to prevent workmen from falling
Scaffolding boards – these are timber boards placed across the transoms or putlogs to create
the working platforms
Toe board – it is a wooden plank placed parallel to the ledger and supported between
transoms for the purpose of preventing materials/operatives from falling/slipping off
from the platform
Coupler – holds together the structural components of the scaffold
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
There should be load bearing and capable of joining 2 tubes together either t right
angles or in parallel
Double Coupler: Used to join ledgers to standards and are the only real load bearing fittings.
Connects standards
Swivel Coupler: This is made up two single couplers riveted together so that it is possible to
rotate them and use them for connecting two scaffolding tubes at an angle.
Putlog Coupler: Mainly for fixing putlogs or transoms to the horizontal ledgers.
Puncheon coupler – are additional vertical to the standards
They do not rest at the baseplate and the base of the scaffold
Various couplers
SCAFFOLD FITTINGS
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
Bridle – additional horizontals between the putlog to cover openings in the wall and thus
provide support for the inner end of the immediate putlogs
Bracings – these are diagonals or cross pieces fixed to ledgers o provide stiffness to the
scaffold (ensure stability for the inner scaffold by removing possibility of movement)
Reveal tube – used where tiers cannot be taken right through to the inside of the construction
• The tube is fixed into an opening in the new and makes a tight fit using reveal pins
and tiers can then be connected
Reveal pin – it is similar to a screw jerk base plate and fitted to each end of a reveal tube to
enable it to be tightened with the opening. It is fitted into the end of a tube to form an
adjustable strut.
Buttresses or struts – they provide anchorage, additional support for increase of stability
Usually fixed at right angles with the line of standards
Split joint pin: A connection fitting used to joint scaffold tubes end to end. A centre bolt
expands the two segments which grip on the bore of the tubes.
Putlog End: A flat plate which fits on the end of a scaffold tube to convert it into a putlog.
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
Types of scaffold
Putlog/builders scaffold/dependent
• made up of uprights set away from the wall at a distance which will accommodate the
required width of the working platform. The scaffold is erected as the building rises.
It is made up of a single row of standards joined by ledgers
Single row of standards is set away from the wall at a distance which will
accommodate the required width of the working platform
Standards are joined together by means of horizontal members or putlogs
The scaffold is erected as the building rises and is mostly used for buildings of
traditional brick construction
Can also be used when repairing brickwork structures as this is the most convenient
type of work to receive the putlog ends and provide the necessary support to the
putlog structure
The height of the lifts is about 1.4m as this is the height at which bricklayers can
conveniently work, and the highest lift erected at any one time should contain the working
platform
Independent Scaffolds
• It has two rows of standards tied by cross members called transoms. It does not rely
upon the building for support and is very suitable for use with framed structures.
Has two rows of standards which are tied by horizontal members called transoms
This type of scaffold does not rely upon the building for support and is therefore
suitable for the use in conjunction with framed structures
• The scaffold should be securely tied to the building
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
Intervals of approximately 3.6m vertically and 6m horizontally
Tying can be achieved by using a horizontal tube called a bridle bearing on the inside
wall across window openings
When sufficient time is unavailable, the scaffold must be slated with raking tube
Mobile scaffold Scaffolds
Are completely self-contained units
Used to provide a working platform of limited size which due to duration of work
carried out needs to be moved frequently e.g. painting
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
These are a force of independent tied scaffold which relies entirely on the building for
support
Are used where it is impossible or undesirable to erect a convectional scaffold from
ground level
The scaffold is supported with a scaffolding structure that projects from the face of
the building and is known as truss-out
The truss-out is anchored on the inside of the building by struts fixed between the
floor and ceilings from which cantilever tubes are projected (needles)
Scaffold frames
These are termed system scaffolds and are based upon the traditional independent
steel tubes
The systems are prefabricated into horizontal or vertical frames
Horizontal frames
Are secured to separate standards by hinges welded to corners of the frame which fit
into special openings
Diagonal bracing can be applied as in normal scaffold
Advantage
Easy to dismantle
Easy to erect even by semi-skilled labourers
Vertical frames
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
He basic frame consists of 2 standards spaced as the normal scaffold and the width is
set apart by cross tubes
The height varies from 0.900 to 1.8mm
These are built ladder style by slotting directly one into another
THE WORKING PLACES REGULATIONS
General regulations to minimum requirements for materials and construction working
places
The scaffolds and its parts should be so designed that it can perfectly withstand and safely
release the vertical and horizontal forces imposed on it either by itself or in conjunction with
local bearing plate
Use should only be made for good and suitable material that has been examined as to its
fitness by a competent person
To enable the scaffold to absorb horizontal forces, it should be reinforced to the longitudinal
and transverse direction by diagonal bracing
A scaffold that is independent should be sufficiently anchored to fixed parts of the building
Connections on scaffolds should join parts so that they can bear the imposed loads
Erection and dismantling to be done by a competent person
Scaffolds should not be used before they have been completed before they are used and after
lengthy interruptions in the work they should be examined for stability and strength
Scaffolds should not be loaded
Timber for platforms must be of adequate thickness and must rest of suitable supports
Working platforms must be boarded in such a way or manner that materials and tools are
prevented from falling off, and this is done also by means of a toe board
The working platforms must be at least 3 board wide (465mm), it should have a good rail and
a toe board
Sufficient and suitable safe means should be used in the times of works and as a result
acceptable metric equivalents apply.
Frequency of inspection
Materials before erection
After completion of the erection of the scaffold
After every 7 days
After severe weather conditions
After any alterations have been made to the scaffold
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
Widths on working platforms for Putlog and Independent Scaffolds
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LECTURER ZOWA T HARARE POLYTECHNIC CIVIL ENGINEERING DIVISION ND CONSTRUCTION
ENGINEERING
IT IS SIGNIFICANT TO PROVIDE A SAFE AND RELIABLE SCAFFOLD FROM
WHICH BUILDING OPERATIONS ARE CARRIED OUT WITH MINIMAL EFFECTS
OF ACCIDENTS
Reference: Construction Technology Volume Two(2) - R.CHUDLEY
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