Risks of increasing use of modern methods of construction

The Fire Sector Federation has a primary interest in fire safety, particularly in the built environment. We note the inquiry is wide ranging, and our response is therefore confined to answering: ‘What are the primary risks to increasing the use of modern methods of construction?’

Forms of modern methods of construction (MMC) are not new and have been around for some time. The past decade has exposed weaknesses, including the loss of total buildings, which provides evidence of risk and vulnerability to fire. There are, of course, practices and standards that can ensure products like prefabricated panels are compliant and used in applications that offer suitable fire protection for the intended purpose.

A culture sometimes apparent in development and construction quarters is that linked to the imperative to build fast and at lower cost to the economy. Although neither innovation nor culture are inherently negative factors they can be, and care is required to ensure society gain the benefits but not the disadvantages of a modern construction methods.

We also recognise the construction sector is one of the most innovative UK sectors. It is constantly exploring, developing and applying technological and scientific boundaries in materials and processes. Indeed, one issue can be the pace of this development and the ability of other sectors, like those seeking to protect and provide resilience against fire, in keeping up to date.

The Fire Sector Federation believes in a principle that designs, materials, products and building processes that have the potential to affect fire safety need to be fit for the required purpose and are properly validated for the intended use. It is this principle that is foremost in our thinking on the use of MMC and the management of the risk of fire.

Fire Risk

Accepting that properly used MMC may offer considerable economic and social benefits, there is a deep concern that increasing the rate of its use would also lead to the possibility of a pro rata increase in the number of fires in MMC buildings. Experience to date has emerged of rapid fire spread and increased levels of damage from the use of forms of MMC with the government’s own report on timber frame construction noting: ‘The result is highly significant indicating that fires in timber-framed dwellings do tend to have a greater area of heat and flame damage on average compared to fires in dwellings of no special construction; i.e. that the differences in proportions observed are extremely unlikely to be the result of chance variation’. ¹

So high is this concern it has resulted we understand in reluctance and a lack of confidence in MMC by investors and insurers.

Such forms of construction open the potential for unseen and uncontrolled rapid fire spread, through cavities and beyond designated fire compartments.² This may endanger lives by compromising structural fire protection and escape route protection to a level where accepted tactical approaches used by the fire and rescue services such as the ‘stay put’ evacuation strategy, so heavily reported upon in the Grenfell Tower fire, are negated.

In short, unplanned deficiencies perhaps directly arising from poor design, procurement and construction techniques surrounding MMC can increase the risk of fire spread. This would impact the life risk to residents, responding firefighters and disproportionate levels of damage.

The impact of using MMC does not necessarily have to be negative, but this increasing risk of uncontrolled fire spread, linked as it is to the use of combustible materials frequently in structural frameworks, requires specific identification, detailed design and ultimately effective control of fire through assertive fire protection.

Additionally, whilst acknowledging that the protection of lives takes precedent over the protection of property in Building Regulations, the evidence of disproportionate damage from fire in MMC buildings has also been noted.³ This gives rise to concern that MMC presents poorer sustainability of the built environment to the UK’s economic detriment given new resources are needed, rather than adaption and re-use, in the construction that follows such fires leading to overall higher costs.

Managing Fire Risk in Modern Methods of Construction

Controlling fire within MMC demands closer examination of a range of factors starting with clarity around the actual definition and control of the combustibility of materials, limiting fire spread by emphasising the effectiveness required in fire barriers and construction separation, and ensuring during construction these detailed requirements are applied, not skimped upon or ignored.

Often in MMC, components form the integral parts of a comprehensive building system, a system that itself may have evolved from design parameters expanded in turn from manufacturers’ tests. Invariably there are limitations to this design process that must be understood if inappropriate scaling up is to be avoided or incompatible products assembled.

This also raises the matter of effective control by regulators and again current concerns exist that UK building guidance and regulations are not sufficiently detailed to ensure safe use of MMC. Common use building materials like plastic can in certain circumstances create pathways for external fires to enter structures or fire barriers and seals may be rendered ineffective by surrounding materials. Guidance and understanding are essential in maintaining effective fire stopping.

The competency of the whole workforce from architect, designers, installers and craft and trades is also central to ensuring MMC is used as intended and the benefits of using active fire suppression, especially where the risk to life is high, as for example where people sleep or are vulnerable because of age or infirmity, are further considerations in mitigating and controlling fire.

Summary

Presently the evidence from fire incidents highlights that some MMC buildings are not as robust or resilient to fire as we might wish. That requires a more pro-active approach to control fire so that society gains positive benefits from building innovation and economic performance.

Conditional on the greater use of MMC should be the application of appropriate safeguards – design and technical specification, compliance to effective standards, use of whole life building control systems, selection and installing of appropriate materials and products, a competent workforce – so that a MMC building’s performance is assessed in the round and not in isolated stages or elements.

That will require looking at international experience,⁴ revisiting regulation, guidance and inspection regimes and systems that assure quality and reaction to fire with a key consideration being limitation and actively mitigating fire spread arising from the current high use of combustible materials.

The Fire Sector Federation is a not for profit society of service and product suppliers who are working together to improve safety from fire in the UK. The author, Dennis Davis CBE, is the Federation’s Executive Officer.

1 Analysis of fires in buildings of timber framed construction, England, 2009-10 to 2011-12 – DCLG https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/66062/Timber_frame_analysis_17_Jan.pdf

2 Fires in cavities in residential buildings – NF51 – NHBC Foundation – 2013

3 Fire performance of new residential buildings – NF36 – NHBC Foundation – 2011

4 BDM14- Fire in timber frame buildings .A review of statistics – FPA 2011

Dennis Davis

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