SpecifiedBy Knowledge Base

Pick and Mix Approach Could Prove Fatal for Building Owners

A building, at all stages of its life-cycle, presents a number of risks, from the initial design and installation stages through to completion, use and ultimate disposal. In addition to eliminating risks for the occupier during the life of the building under CDM (Construction Design Management) Regulations, the products and practices involved must be thoroughly assessed for any risks. It is the responsibility of the client, architect and main contractor to assess these risks and advise the entire team of any areas for concern.

Working with main contractors who understand the risks makes it easier. Many main contractors understand the value of a specification and the reasons why adhering to that specification will ultimately save them from having to deal with future conflicts.

With an increasing number of main contractors encouraging roofing and cladding suppliers to break specifications, in order to reduce costs, there has been a rise in the trend towards an ‘80s style ‘pick and mix’ approach to projects.

The risks associated with this practice are either overlooked or not properly understood. While the cladding contractor may prefer the cheaper option, or choose to forego quality for higher margins, the ultimate responsibility for cutting corners when the building fails will remain with the investor, developer and tenant.

Safety (Non-Fragility)

In the event of injury or fatality, each link in the supply chain will be examined to ensure that every effort was made to follow best practice. Allowing a cladding contractor to install an untested assembly of components is dangerous and leaves the entire team at risk of prosecution.

For this reason, the Advisory Committee of Roof Safety (ACR) along with the Health & Safety Executive (HSE) commissioned and published material standard ACR[M]001:2000 ‘Test for Fragility of Roofing Assemblies’, which has since been superseded and is currently in its fourth edition the ACR[M]001:2011 ‘Test for Non-Fragility of Profiled Sheeted and Large Element Roofing Assemblies’. It is important to note that a roof can only be claimed to be Non-Fragile, and therefore safe, when it is tested as a complete roof assembly, not just the external sheet, liner panel or rooflight in isolation.

To ensure nobody can fall through a roof, either during construction or for a pre-determined period of time after construction, all roof types need to be tested according to the manner in which they will be installed. For example – if the roof has differing purlin spans, an array of spans within these parameters MUST be tested individually to ensure that, in the event of a fall from height, the person or persons involved will not fall through the roof to the ground.

It is important to note that the profiler or panel supplier cannot claim Non-Fragility on a singular component. Neither can companies that make rooflights claim that their product, in isolation, is Non-Fragile. It is only the installed assembly, including the profiles, rooflights, fasteners and sealants, when tested as a whole, that can be deemed Non-Fragile if it passes the necessary tests.

When the cladding contractor or main contractors choose to change a specification and install replacement components, which they have selected, it is incumbent on them to test the alternative system in full, at all purlin spacings. If the system has not been tested it must be deemed fragile!

Furthermore, the choice of rooflights and their compatibility with the surrounding roof must be understood.

Two key issues which need to be considered and understood are as follows:

In-plane rooflights – GRP is without doubt the preferred solution of most, if not all, of the UK’s rooflight manufacturers as its expansion and contraction features are similar to that of steel. Polycarbonate, on the other hand, expands and contracts six times more than steel. GRP and plastisol are compatible, unlike polycarbonate which leads to major issues as it is attacked by the plasticisers within the plastisol coating resulting in premature rooflight degradation which could render the rooflight unstable. It may be claimed that the roofing contractor should isolate the two, which can be done, but not using PVC tape. Contact between the two materials is unavoidable due to the contraction and expansion caused by variations in temperature, which inevitably breaks the isolation and the detail fails. It can, therefore, be concluded that these two materials should never be used in this application.

Out of plane with Barrel or Domed Rooflights – expansion and contraction is controlled with these rooflights as there is no contact with a plastisol coated steel product, therefore, compatibility is easily managed. Unlike in-plane rooflights, where GRP is the preferred option, polycarbonate is a good choice for barrel and domed rooflight installations.

The client, architect and main contractor should be able to demonstrate that, in the event of a serious accident resulting in a fall through one of their roof systems, they have taken adequate care to deliver and install a Non-Fragile design.

ACR[CP]001:2007 Rev3 ‘Recommended Practice for Work on Profiled Sheeted Roofs’ contains within its guidance an aide memoire for designers, specifiers and inspectors. This is a document that should be added to every specification, requesting that the successful roofing contractor completes the Annex C questionnaire to prove compliance for the entire system. In the event of an accident, which could result in a fatality, the completed questionnaire can demonstrate what they have deemed appropriate in relation to due care and attention.

In addition to the system design itself, any proprietary system fitted to the roof must also be tested as a complete assembly. One such example of this would be when installing a Horizontal Life Line (HLL) system, the forces that are transferred, should someone fall when attached to these systems, are significant and the structure must be capable of absorbing the energy. It is for this reason that the complete assembly is tested – ACR Magenta Book.

People are still falling through roofs which have been assembled without due care and attention resulting in serious injury, or worse. Cost reduction ‘value engineering’ is no excuse for taking unnecessary risks.

Thermal Compliance (U-value and Psi value)

In order to meet government regulations and pass building control, the thermal performance of the building envelope is critical, in proving compliance. Elemental U-values, for roof and wall cladding systems for example, must be calculated based on project specific information, such as secondary steelwork spacings. Taking the thermal performance of the insulation in isolation is NOT proof of compliance. Thermal bridging within the insulation zone spacer system and/or fixings can have a dramatic impact on the result. Without calculating the construction in its entirety, compliance cannot be proven.

In addition, without knowing the thermal performance of the adjoining systems it is also impossible to provide accurate psi-values which include the linear perimeter details.

If an untested and unproven system is used, the occupier of the building will ultimately bear the cost for any discrepancy resulting from reductions in thermal performance, and ultimately increased heating demand, and higher running costs.

Independent Certification (BBA and LPCB)

Independent verification from companies such as the British Board of Agrément (BBA) provides impartial confirmation that important features of the products or systems have been assessed. This will reassure the specifier that the products being used are performing (thermally, structurally, etc) as per the manufacturer’s claims. It is important to note that verification of individual components, such as the external sheet material, will at best be achieved when fitted in a certain application, the results will be affected depending on how the cladding contractor chooses to assemble the component.

Using a myriad of components from different manufacturers to assemble the cladding system puts the onus on the cladding contractor to ensure that it performs structurally for the life of the building. Where costs are tight, a structural engineer may be bypassed with the cladding contractor relying on their own ability to review load span tables for liner panel, spacer system and external sheet to determine what is acceptable. Using a tested, independently verified system removes any risk allowing the correct spacing and fixing methods to be adopted.

Guarantee – (System, Coating, Flashing and Fixing)

The validity of many guarantees and warranties, currently in circulation, are a major cause for concern throughout the construction sector.

Warranties, in the main, have no legal standing as they claim that what is warranted should perform. In the event that it does not perform the company supplying the warranted system or product has no legal responsibility.

Insurance backed warranties or even guarantees which apply unreasonable terms and conditions, such as extreme temperature parameters or mandatory annual inspection requirements, are commonplace leading to them being breached on a regular basis and rendering them null and void.

Very few building occupiers or owners maintain or inspect their buildings annually and they only become aware that they have breached the terms of their guarantee/warranty when something goes wrong and their claim is denied. The industry should be pushing for meaningful guarantees at every stage of the project, not searching for the cheapest solution which will end up costing the owner or tenant in the long-term.

In addition to these differing guarantee options the risks which are associated with using a myriad of components from different manufacturers poses an even greater risk. When a claim is being made the time and cost associated with contacting all these manufacturers and arranging co-ordinated site visits can be difficult. The likelihood is that the manufacturers involved will try and blame someone else for the problems and often resolving the issue is impossible. Using a system with all components supplied from a single manufacturer eliminates these issues.

Conclusion

The use of ‘pick and mix’ systems on industrial, commercial and retail schemes ceased many years ago, as professionals in the procurement and specification chain strived to ensure that the building was delivered to the correct standards and with minimum risk.

While the recession has re-introduced a need to take greater risk in the hope of survival, companies must understand that by taking this risk they are buying in to sub-standard practices hidden by worthless guarantees and warranties and, in the worst case scenario, they are putting lives in danger through poor roof installation. It is incumbent on the specifier to halt this dangerous spiral downwards and bring sanity and value back to the specification process.

Roof and wall cladding system manufacturers/suppliers, at best, provide all of the tested components along with the appropriate certification and test data. Some choose to name a selection of components and trust that these products will be incorporated into the design but there are no certainties that this will happen, as it is effectively left with the contractors, not the manufacturers.

About the Author: David Hicks, an independent Roofing and Cladding consultant, produced this article on behalf of the Metal Cladding and Roofing Manufacturers Association (MCRMA).

Find them on Twitter @MCRMA1

If you have found this article useful, sign up to receive updates on our latest posts by email below.

 

Get Our Latest Blog Posts by Email

* indicates required



SpecifiedBy Editor