Jade Industrial
Unit 19
Ashbourne Industrial Estate
Ashbourne,
Co. Meath

Tel: 01 801 0784
Fax: 01 8359006

SCAFFOLD DESIGN

Introduction

With our scaffold designs we are committed to providing a fast professional service. Our Chartered Engineers designs comply with the most up to date codes of practice, regulations and health and safety legislation.

We can meet you on site to discuss your scaffolding/temporary works design requirements.
We can provide a quick turnaround of drawings.
We can also attend site to certify that works comply with our design and provide completion certificates.
We use computer aided design software that has been customised for scaffolding to produce professional tender and construction drawings.

Please do not hesitate to contact us to discuss your requirements or a particular project.

About us:

Our qualified Scaffold Design Engineers can provide our clients with a full scaffold/ temporary works design service including structural design and Autocad drawings.

Main Contractors:

We can discuss your scaffolding needs and provide a complete tender drawing package so that you can get accurate quotes from a range of scaffolding contractors for fixed price projects minimising your exposure to unforeseen costs.

Public Sector Clients:

We provide technical support, detailed design calculations and drawings where you need to demonstrate the structural integrity of your proposed temporary structure.

Reasons to call us:

High loading of scaffolds
Sheeted scaffolds
Protection fans
Large spans
Cantilevered scaffolds
Trussed out scaffolds
Suspended scaffolds
Drawings required for third parties (adjoining property owners)
Scaffolding audits
Difficult site constraints
Temporary roofs
Spectator terraces
Footbridges

When does your scaffold require a design?

This article written by us was published in ‘Construction’ magazine in October/November 2009.

When it comes to industry awareness of the need for a scaffold design we have found that in general Contractors fall into four categories.

Those who know that their scaffold needs a design and know how to go about getting it done.
Those who know that their scaffold needs a design but are unsure about how to get it done.
Those who are unsure as to when a scaffold requires a design.
Those who do not realise that some scaffolds require a design.

We have classified types of scaffold to make it easier for Contractors to know what level of design their scaffold requires.

Class A: Basic Scaffold

When a system scaffold can be erected in strict accordance with the manufacturer’s user manual and instructions, the scaffold will need no further design.

Class B: Designed Scaffold

Class B1: Localised design

When the scaffold deviates slightly from the manufacturer’s user manual, e.g. where a required tie position is not possible due to the presence of a window or other obstruction to tying the scaffold to the building, a design for this section of the scaffold is required.

Class B2: Full design

When the scaffold deviates from the manufacturer’s instructions or contains one or more of a non-exhaustive list of features like protection fans, cantilevers or trussed out sections, a full design is required for the entire scaffold.

Following the withdrawal in 2004 of BS5973 ‘Code of practice for access and working scaffolds’ which has now been replaced by Eurocode IS EN12811-1 ‘Scaffolds – Performance requirements and general design’ the National Access and Scaffolding Confederation (NASC) published TG20:05 ‘Technical guidance on the use of BSEN12811-1 Guide to good practice for scaffolding with tube and fittings’. ¹ In November of last year NASC published a revised edition of this guidance document, TG20:08.

The new document has been divided into two volumes. Volume 1 provides practical advice, information and conditions for basic tube and fitting scaffolds that can be built without calculation. Volume 2 provides technical information and advice required for the design of scaffold arrangements outside the range of volume 1.

TG20-08 states that ‘all scaffolds shall be designed except for basic scaffolds’.

A basic scaffold is one that conforms to the criteria set out in volume 1 of TG20:08 and is therefore a class A scaffold (see above). If the scaffold is classed as a basic scaffold the allowable height may be calculated from volume 1 of TG20:08, otherwise it is a class B scaffold and will require a design. Likewise, the Irish ‘Code of practice for access and working scaffolds’ states that ‘general access scaffolding , erected in accordance with the manufacturer’s instructions does not require any further design, however if a design is required then a competent scaffold designer must be engaged to design the scaffold’.

We have recently worked on projects where the Health and Safety Authority (HSA) checked that the Project Supervisor for the Design Process (PSDP) had liaised with us as the Scaffold Design Engineers. Under the ‘guidelines on the procurement, design and site management requirements of the safety health and welfare at work (construction) regulations 2006’ the key role of the PSDP is to ensure co-ordination of the work of designers throughout the project. The co-ordination of the scaffold design and the permanent structure design is vital in terms of applied loading and sequencing of works.

In many cases scaffolding is erected, either wholly or partly on the permanent structure. Consideration is not always given to the scaffolding loads that are applied to it. In all cases the permanent works designer should be given the applied loading on the structure and should check that it can support the scaffold. In some cases (e.g. where the scaffold is supported on a suspended slab) the number of working levels on the scaffold may need to be reduced or temporary spreader beams may need to be placed under the scaffold to distribute the load across the slab, alternatively the slab may need to be back propped from below. It is essential that all parties co-ordinate their designs and sequencing of works to ensure that the existing structure is not over loaded.

In the last year we have seen cases where the HSA have asked Main Contractors to provide a design for a standing scaffold.

Producing a drawing for a standing scaffold when work has already commenced on site, mean delays to the programme which are costly.

It is more cost effective and safer to produce a scaffold design and drawing at the start of the project, avoiding delays during construction.

Another way that Main Contractors can minimise cost is by producing scaffolding tender drawings so that accurate and comparable quotes from a range of Scaffolding Contractors can be got, minimising exposure to unforeseen costs.

In conclusion, it is vital that Main and Scaffolding Contractors are aware of which situations will require a scaffold design and all members of the design and construction team should be proactive in ensuring the co-ordination of the temporary and permanent works designs.

1. The Eurocodes form a common European set of design codes which replace existing national codes. Each country has its own ‘National Annex’ which contains information specific to that country.

For example:

BSEN12811-1 - ‘Scaffolds – Performance requirements and general design’ is the Eurocode for Britain containing the British national annex.

ISEN12811-1 - ‘Scaffolds – Performance requirements and general design’ is the Eurocode for Ireland containing the Irish national annex.

Written by: Georgina Molloy BSc. Eng. CEng.

Chartered Engineer

Jade Industrial Contracting

Written Scaffolding Design Brief

This is an example of the information that we ask our clients to provide when we carry out a scaffold design.

Where can we view your scaffold management plan?
What is the site location and location of scaffold on site?
Load class of scaffold and required use of scaffold. Nature of any plant to be used on the scaffold. If the scaffold has a loading bay will it be loaded by mechanical means.
Length and height of the scaffold.
Does the scaffold require sheeting or debris netting?
Existing permanent structure/proposed structure drawings.
Nature, stability and capacity of the supporting ground and/or supporting structure.
Number of working levels required.
Number of boarded levels required.
Duration that the scaffold will be standing for.
The presence of any hidden hazards that might create unexpected risks to scaffold erectors and/or users.
Do platforms need to be covered in plywood or a similar material?
Is stairs or ladder access required?

See below a list of scaffolding codes of practice, sources of information and links to the websites where the documents can be downloaded or purchased.

‘Code of practice for access and working scaffolds 2008’ – HSA

Free to download from:

Download Here

I.S. EN 12810 Part 1 2004: Facade scaffolds made of prefabricated components – Part 1:Product specification.
I.S. EN 12810 Part 2 2004: Facade scaffolds made of prefabricated components – Part 1:Particular methods of structural design.
IS EN 12811 Part 1 2004: Temporary works equipment – Scaffolds – Performance requirements and general design.
IS EN 12811 Part 2 2004: Temporary works equipment – Part 2: Information on materials.
IS EN 12811 Part 3 2004: Temporary works equipment – Part 3: Load testing.

Available to purchase from: www.standards.ie

TG 20:08: Guide to good practice for scaffolding with tube and fittings-technical guidance on the use of BS EN 12811-1

Available to purchase from http://www.nasc.org.uk/TG20_Launch

Scaffold Management Plan -

Yet to be developed

Main Contractors Responsibilities.

Yet to be developed

Code of practice for access and working scaffolds 2008 – PSCS/user summary.

The Main Contractor is responsible for defining a policy in relation to scaffolding. He is required to carry out a risk assessment and put a scaffold management plan in place. We have extracted and summarised relevant information from the code of practice. (See attached link to pdf document).

Scaffold ties - with shear

Scaffold ties are now required to resist tension (pull), compression (push) and shear. See section 2, Volume 1, TG20:08 (website link provided above).

Pictured here is one of our Heavy Duty Shear resitant ties.

Shear capacity is dependent upon the base material being drilled into.
Tension/compression capacity is dependent upon the base material being drilled into.