BCSA Guide to the Installation of Deep Decking

7/27/2019 BCSA Guide to the Installation of Deep Decking

1/14

BCSA Guide to theInstallation of Deep Decking

BCSA Publication No 44/07


2/14

BCSA Guide to the

Installation of Deep Decking

Apart from any fair dealing for the purposes of research or private study or criticism or review, as permitted under the Copyright Design and

Patents Act 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission

of the publishers, or in the case of reprographic reproduction only in accordance with terms of the licences issued by the UK Copyright

Licensing Agency, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organisation outside the UK.

Enquiries concerning reproduction outside the terms stated here should be sent to the publishers, The British Constructional Steelwork

Association Ltd. at the address given below.

Although care has been to ensure, to the best of our knowledge, that all data and information contained herein are accurate to the extent that

they relate to either matters of fact or accepted practice or matters of opinion at the time of publication, The British Constructional Steelwork

Association Limited, the authors and the reviewers assume no responsibility for any errors in or misinterpretations of such data and/or

information or any loss or damage arising from or related to their use.

Publications supplied to members of BCSA at a discount are not for resale by them.

BCSA Limited is the national organisation for the steel construction industry: its Member companies undertake the design, fabrication and

erection of steelwork for all forms of construction in building and civil engineering. Associate Members are those principal companies

involved in the purchase, design or supply of components, materials and products related to the steelwork contracting industry. The principal

objectives of the Association are to promote the use of structural steelwork; to assist specifiers and clients; to ensure that the capabilities

and activities of the industry are widely understood and to provide members with professional services in technical, commercial, contractual,

quality assurance and health & safety matters.

The British Constructional Steelwork Association Ltd.,

4, Whitehall Court, Westminster, London SW1A 2ES.

Telephone: (0) 20 7839 8566 Fax: (0) 20 7976 1634.

E-mail: [email protected]

Website: www.steelconstruction.org

ISBN 10 1 85073 546 8

ISBN 13 978 1 85073 546 5

British Library Cataloguing-in-Publication Data.

A catalogue record for this book is available from the British Library

The British Constructional Steelwork Association Ltd

BCSA Publication No 44/07


3/14

BCSA GUIDE TO THE INSTALLATION OF DEEP DECKING

2

CONTENTS

SECTION TITLE PAGE

1 INTRODUCTION 3

2 DESIGNER INPUT 3

3 PLANNING FOR SITE INSTALLATION 4

4 SITE SET UP 4

5 FALL PROTECTION 5

6 SUPPORTING STRUCTURE 6

7 WEATHER CONDITIONS 6

8 ACCESS SYSTEMS FOR INSTALLING

DIAPHRAGM END PLATES 6

9 INSTALLATION OF DECKING SHEETS 7

10 CUTTING DECKING SHEETS 8

11 SEALING AND FINISHING OFF 8

12 SEAM STITCHING 8

13 EDGE PROTECTION 9

14 REMOVAL OF WASTE 10

15 DECKING AND EDGE TRIM FASTENERS 10

16 FIXING EDGE TRIMS 11

17 TEMPORARY PROPPING 11

ACKNOWLEDGMENTS 12


4/14


3

1 INTRODUCTION

Deep decking profiles differ from traditional shallow decking in that the decking sheets are all single span and generally

sit in the bottom flange of the supporting beams with pre-fitted end diaphragms. This system requires a different method

of work for site installation from that employed for the installation of shallow decks.Deep decking has advantages over shallow decking in that it will span greater distances without propping, but the

additional work on site associated with the installation of diaphragms and closures does not necessarily mean that

installation is more labour intensive.

The recommendations in this guide are supplementary to the BCSA Code of Practice for Metal Decking and Stud Welding

publication number 37/04.

2 DESIGNER INPUT

There are a number of issues that building designers need to address when specifying deep deck systems as the

preferred means of flooring construction.

It is important that the designer and steel fabricator follow standard details for Corus deep decking to ensure the safe and

efficient installation of the decking and floor slab. For further information or assistance please refer to Metal Cladding &

Roofing Manufacturers Association (MCRMA) or the Steel Construction Institute (SCI) publication on slabs and beams

using steel decking:Best Practice for Design and Construction SCI-P-300 at Corus website www.corusconstruction.com

The steelwork detailers should recognise that some additional bottom flange details need to be changed to allow deep

decking to be fitted. The end bearings are always a recognised requirement but the side bearings are not always considered.

The Corus preferred details are available from the Corus web site.

The requirement for ledge angles to be fitted in the appropriate places for side support is easier to address during the

steelwork fabrication stage than on site. Some details also make it impossible to access with the low-velocity powder

actuated fastener tools used to secure the edge of the sections. This is also a factor when hollow sections are positioned

within the area to be concreted.

Examples of Corus preferred details


5/14


4

3 PLANNING FOR SITE INSTALLATION

Pre-assembly of deep decking is possible when sufficient space is available on site to enable decking bays to be

assembled at ground level prior to lifting into place, and the regular use of a suitable crane is available for lifting.

Pre-assembly removes the need to pre-fix the end diaphragms and enables most of the work to be carried out withoutworking at height. However, if this process is to be considered then early detailed discussions must be held between the

Principal, Steelwork and Decking Contractors, as pre-assembly requires a radical change to the planning, programming

and construction process.

In most cases pre assembly will not be possible and other measures should therefore be taken to reduce work at height

as far as is reasonably practicable. Work should be planned and programmed to allow the end diaphragms to be installed

from mobile elevating work platforms (MEWPs) or mobile access towers (MATs) wherever reasonably practicable.

Where the steel configuration allows it may be possible to work at the second level first, through the first level steelwork.

The risk associated with using ground - operated MEWPs through the steelwork will preclude their use at higher levels

from the ground. In all cases this will require ground conditions to be sufficiently sound for the proposed equipment

to be used.

4 SITE SET UP

Work should be planned so that no other trades or stored materials are permitted onto the deck and no other works are

carried out immediately above or below the working area until it has been completed and handed over. The area

immediately below the works should be zoned off using bunting tape and signs, to create an exclusion zone.

Examples of the pre assembly and lifting of decking


6/14


5

The Decking Contractor will provide drawings showing where the decking packs need to be positioned when loaded out.

The decking packs are delivered with the bottom sheet 250mm longer than required so it can be safely loaded out onto

the steel frame with sufficient bearing to allow it to sit on the top flange of the steelwork. The Steel Erection Contractor

will need to ensure the decking packs are positioned in accordance with the drawings provided, in order to minimise the

need for deckers to traverse the steelwork.

Wherever possible, the decking installation should be planned to commence from the corner of a building or phase, so

that the number of leading edges is limited. The edge protection and access point will have been installed prior to work

commencing, thus effectively enclosing a safe area of work for decking operatives to work within.

The safety net system (if applicable) will need to be installed before the decking work commences, but not before the

attachment of the end diaphragm plates (see section 5 below).

5 FALL PROTECTIONSafety netting is the preferred method of fall protection for the installation of deep decks, as it provides passive and

collective protection for operatives working above. Where safety nets are used they act as primary fall protection,

and there will be no requirement for the Decking Contractor to use additional measures such as running lines. The safety

net system should be installed directly onto the bottom flange of the steelwork that the decking is fixed onto, thus limiting

the height of any potential fall to a minimum.

The installation of safety netting can follow the installation of the end diaphragms as the safety net anchors (Grippa or

similar) clamps will fit over the base plate of the end diaphragm. This is made possible by installing the diaphragms from

a MEWP or MAT prior to installing the netting (see section 8). This method of work will require close cooperation andcoordination between the deckers and the safety net riggers. It should be noted that MATs must never be used for the

installation of safety netting; ladders can safely be used in some circumstances and the Health & Safety Executive (HSE)

have published a guidance document Safe use of ladders and stepladders INDG 402.

Further guidance on the most appropriate fall protection is available from the Fall Arrest Safety Equipment Training

(FASET) Best Practice Guide The selection of access methods to install and dismantle safety netting.

When safety netting is used, it is also good practice for decking operatives to wear full body harnesses and the

appropriate lanyards for use where a residual risk of falls from height exists, i.e. during the installation of cantilever edge

trims beyond the safety net zone where it is necessary to reach through the handrails etc.

The Installation of Netting


7/14


6

6 SUPPORTING STRUCTURE

Deep decking is installed in single spans and located onto end diaphragms which have been pre-fixed to the lower flange

of the support beams. The minimum bearing requirement for the decking is 50mm on steelwork. The diaphragm back

stop is greater than 50mm and the deep decking must be centred so that an equal bearing is provided at both ends.Additional structural support is usually required to the web of columns to take the end bearing of the decking sheet and

close off gaps. Whilst the Decking Contractor can assist with highlighting where additional support is required, it is often

too late to have these supports or alterations added to the steelwork, as it has often been fabricated by the time the

decking contract is awarded. The designer and steel fabricator should therefore refer to Corus standard details from

www.corusconstruction.com during the design stage to ensure that unnecessary additional costs of alterations are not

incurred at a later date. Consideration should be given to the following:

Installation of net attachment points

Box section flange extensions that are suitable for use with nets

Change of details required where standard beams are used rather than Asymmetric Beams (ASBs)

7 WEATHER CONDITIONS

Decking packs should not be opened if all the sheets in the bundle cannot be fixed or left in a safe condition at the end of

the shift. During periods of freezing weather, heavy rain and/or high winds, the decking installation should not commence

until the site foreman has inspected the working area and, using his experience, has assessed it fit to start work.

All ancillary items such as trims closures etc must also be suitably restrained during periods of high winds and

at the end of each shift.

8 ACCESS SYSTEMS FOR INSTALLING DIAPHRAGM END PLATES

End diaphragms are manufactured in 1800mm long sections consisting of three rib closures. These closures must be

installed in advance of the decking to the lower flanges of the beams on both ends of the steelwork bay, and fixed into

place using two fixings at pre-marked positions for each length. Each length must be fitted accurately so that the 600mm

pitch of the decking section is located as shown on the decking layout drawings.

The diaphragm end plates should be installed from a work platform wherever reasonably practicable as this will greatly

reduce the risks associated with working at height. Access systems such as MEWPs or MATs can be used if the ground

conditions are levelled and compacted, including the areas around the column bases. Particular attention may be needed

when assessing a suitable powered access system for low floor heights, as there is a risk of entrapment between the

basket and the steelwork will be higher if the floor heights are low.

For upper floors on multi-storey buildings MATs may be used, providing the decking below remains clear from materials

and other obstructions. On larger multi-storey buildings it may be possible for the floors to be cast to allow small MEWPs

to be utilised. Consideration will need to be given to how these machines will be lifted in and out of the floors, and

designers must check the floor slab to ensure it can take the imposed loads of the chosen machinery.

On completion of this element of work the safety net fall arrest system can be rigged as described in section 5.


8/14


7

9 INSTALLATION OF DECKING SHEETS

Decking installation will only commence once the end diaphragms and safety net fall arrest system are in place.

When commencing decking installation the operatives will use the access which should be provided adjacent to the set

out point which will be denoted on the decking layout drawing. The first bundle of decking to be laid will have beenloaded out so that it is immediately available from this location, thus reducing the need for operatives to traverse the

steelwork. The bundle supporting longer sheet (bay length +250mm) will be the last to be installed and will be cut down

to the required length prior to installation.

Decking operatives will usually stand on the top flange of the beam at either end of the first bundle of decking, and will

cut open the steel banding, as it is not possible to straddle the steelwork on most occasions once the end diaphragms

are in place. The first decking sheet will then be lifted out onto the steelwork and placed over the pre-fitted end

diaphragm by a minimum of two operatives, one at each end of the decking sheet. Where practicable two operatives at

either end of the decking sheet should be employed using an extended handlebar lifting device. If mechanical lifting

systems are able to be installed safely then they should be the preferred option.

Once in place this sheet will then be used as a working platform from which to lay the remaining sheets.

Decking operatives will then stand on the beam immediately adjacent to the end diaphragm that the sheet will be placed

over whilst lowering the decking sheet into position. Decking sheets must always be manoeuvred into position by two

operatives. Once the decking sheets have been laid and lapped together and temporarily fixed into place, the safety nets

and clamps can be removed. The decking will then be fully fixed into place using a cartridge tool and two heavy duty

nails per panel end.

On completion of the first bay of decking the second bundle of decking sheets should be immediately accessible.

This will allow the bundles banding to be removed whilst the decking operatives remain on the previously laid decking.The installation process will then be repeated. When installing decking bundles running parallel to one another,

one decking operative will be able to use the first bundle laid as a position of work for splitting and laying the adjacent

bundle, the second operative will work as described for the first bundle.

Decking installation should always cease a minimum of two metres back from any unprotected edge, such as the end

of a safety netted work zone.

It is critical that the Decking Contractors drawings are strictly followed during installation, particularly the set out of each

bay, as the decking will have been detailed to take account of the services and/or openings that may be run through the

underside of the decking trough, or be formed in the crest of the decking at a later date.


9/14


8

10 CUTTING DECKING SHEETS

Decking sheets should be detailed so that they are delivered to site at the correct length. In most instances, the only

on-site cutting required other than the bundle supporting sheet should be cutting in around columns and otherprotrusions in the floor, or where decking is to be fitted to splay bays.

The first and last sheets in each bay will usually require notching to fit around the columns, this should be the last

operation in each bay so that the cutting may be carried out on the safe working platform created by the rest of the

decking sheets previously laid out. On-site cutting will normally be carried out using petrol driven disc cutters. The use

of electric angle grinders is not usually recommended except in areas of poor ventilation, because this equipment tends

to be more awkward to operate and can take two or three times as long to make the cut. There is also little significant

noise reduction from using such tools.

11 SEALING AND FINISHING OFF

The ends of the decking sheets are generally closed off by the end diaphragms when viewed from underneath.

On completion of the decking it will be possible to see gaps between the crest of the decking and the end diaphragms.

Small gaps such as these will tend to close off when the weight of the concrete is applied. The decking is not intended

to provide a watertight seal and a degree of fines and water seepage should be expected from the panel ends and joints.

The deckers will seal off the larger gaps at the trough re-entrant and end diaphragm.

In other areas of the decking i.e. cuts around columns, gaps up to 5mm are generally acceptable, as they are not

sufficient to allow concrete aggregate to escape. Gaps in excess of 5mm will generally be filled using expanding foam;

the Decking Contractor should provide a COSHH assessment and suitable PPE, including gloves and protective clothing,

to cater for the use of the foam.

12 SEAM STITCHING

Seam stitching between decking panels is required to minimise concrete seepage. and to hold the lips of the decking

together during concreting operations. Seam stitching will be carried out as soon as practical following the installation

of the decking using self drilling self tapping steel screws at 500mm centres for ComFlor 225.

Edge Trim Fitted


10/14


9

13 EDGE PROTECTION

The location of the perimeter edge protection needs to be considered at an early stage, and should be fitted at an offset

from the perimeter beams as the deckers need to work off the perimeter beams to lay the decking sheets. Edge trim is

also often fitted to the outside toe of the perimeter beams which requires deckers to lean out beyond the edge protection.Any scaffolding therefore needs to be positioned so that it does not foul the installation of the trim.

The edge protection should not be fitted to the inside of the perimeter columns or centre line of steelwork. This makes

the fixing of the edge trim ergonomically difficult and increases the likelihood of materials falling when the deckers install

the edge trims.

Where full floors cannot be completed, for example where the building is split into different phases, consideration should

be given to the provision of phase edge protection. Where steelwork has been erected, it is acceptable to extend a safety

net fall arrest system out beyond the perimeter of the decking zone provided that it can extend a minimum of 2m and the

fall height is less than 1m. As soon as the decking is laid, temporary barriers should be positioned 2m back from the

decking edge to demarcate the safe working zone within which others can work from.

On multi-storey structures, Principal Contractors should be made aware of the pyramid effect that occurs when using

this method as the effective working area reduces on each floor. Where this occurs the use of temporary fixed phase edge

protection should be considered. On completion of an area or phase, the fall arrest system should be removed oncea check has been made to ensure all small openings and voids created in the floor have been adequately hand railed

or boarded out.

The Principal Contractor should also give careful consideration to the provision of edge protection with three rails rather

than toe boards to perimeters and internal openings. Deep decking sits in the bottom flange of the steelwork it is unusual

for the edge trim to be able to act as a toe board (as it usually does in shallow decks), as the edge trim will usually finish

at the height of the beam or just above. The requirement for the toe boards will be more relevant to the area on

completion of the flooring when it becomes a working platform.

Typical Edge Protection


11/14


10

14 REMOVAL OF WASTE

A skip should be available, at or adjacent to the working level, for the disposal of waste materials. Care should be taken to

ensure that a skip is located securely over the structural steelwork and not loaded directly onto the decking as all deep

decking is single span. If a skip is not available, the Decking Contractor will be required to gather the scrap together inone neat pile at each level for disposal by others once suitable means of removal are available. The skips should be

arranged to arrive as soon as possible following the start of the decking work.

On single storey structures, a controlled drop may be permissible, subject to assessment of the risks and the inclusion

of a suitable procedure in the method statement. It should be noted that off-cuts of decking and edge trims are extremely

sharp and can be hazardous to move long distances. The distance to the skip should therefore be kept to a minimum.

Scrap should never be carried down ladders or over long distances across the site. Protective gloves must be worn

at all times whilst handling decking or edge trims.

15 DECKING AND EDGE TRIM FASTENERS

The decking must be fixed at the following locations:

End diaphragms must be fixed to the supporting steelwork using two heavy duty fixings (Hilti ENP2 or Spit SRB14),

one at either end. The diaphragms are predrilled with locating holes to aid this process.

ComFlor 225 decking sheets must be fixed into place using two heavy duty fixings (Hilti ENP2 or Spit SRB14) to

each end of the decking sheet through the trough of the decking.

ComFlor 225 decking crest must be screwed to the top return of each diaphragm using two self drilling self tapping

steel stitching screws minimum 16mm long.

The ComFlor 225 decking sheet side lap must be stitched at 500mm centres using self drilling self tapping screws

minimum diameter 5.5mm, minimum 25mm long.

Edge trims, closure plates and straps should be fixed to steelwork at 500mm centres using powder activated

fasteners as below or self drilling self tapping steel stitching screws minimum 16mm long.

Fixing of the decking and edge trim to the supporting steelwork will usually be carried out using low-velocity powder

actuated fastener tools, commonly known as shot firing. Hilti ENP2 or Spit SRB 14 heavy duty nails must be used for

securing the decking in all cases. This method provides a safe and economical method of fixing-down the decking.

The operators must be fully trained and competent to use these tools.

Where the use of powder activated cartridge tools is not permitted, self drilling self tapping screws are used to secure

the decking. However, it should be noted that this method is time-consuming and may have an impact on the overall

installation programme, particularly when fixing to steels with 10mm or thicker top flanges, as these will need to be

pre-drilled with a pilot hole to allow a successful fix. In addition, this methodology will lead to ergonomic difficulties,

because the decking operatives would be bent over below the level of their feet for much of the working day. This change

to the work method will also introduce considerable hand arm vibration risks.


12/14


11

16 FIXING EDGE TRIMS

Edge trims are usually supplied in 3m lengths of the appropriate gauge pressed steel in accordance with the Corus

details available from www.corusconstruction.com which may be cut down on site to suit the steelwork configuration.

Each length should be fixed to the perimeter beams with the edge restraint straps fixed at 500mm centres.The deckers should take care to ensure that the restraint straps are tight, thus preventing the trim from bowing out during

concrete placement. Edge trim positions are generally set out from the centre line of the supporting steelwork and should

be fixed with a tolerance of +/- 10mm in accordance with the BCSAs National Structural Steelwork Specification for

Building Construction.

17 TEMPORARY PROPPING

Temporary propping is specified by the structural engineer at the design stage and will be denoted on the decking

contractors construction issue drawings. In general deep decking will span approximately 6.00m without support. For spansin excess of 7.5m the temporary props should be in place and suitably braced prior to the installation of the decking.

In all cases it is important that:

The decking is propped in a continuous line at right angles perpendicular to the deck span, extending the full width

of the bay supporting each decking rib and any Z trims present.

The propping systems are of adequate strength to carry the slab and are assessed by a competent person.

Bearers should be an adequate width as described in the Corus information available from

www.corusconstruction.com (minimum of 100mm wide).

Propping systems should not be removed until the slab has reached 75% of its characteristic strength

(normally between 7-14 days).

Edge Trim

A Propping System


13/14


12

ACKNOWLEDGMENTS

This guidance document has been produced with the special assistance of:

Adrian Wallwork Corus Panels and Profiles

Neil Tilley Corus Construction & Industrial

David Singleton Northern Steel Decking

Derrick Robinson Robinson Construction

Clive Phillips Studwelders

Derek Mullett Studwelders


14/14

BCSA Guide to the Installation of Deep DeckingBCSA Publication No 44/07

BCSA Guide to the Installation of Deep Decking

Documents