More than one in five fatalities (22%) resulting from falls from height in the construction industry involve people falling through fragile material. The HSE says that, on average, one person a month dies at work after falling through a fragile roof or rooflight.

And it isn't just roofers and other construction workers who are at risk. Boiler and plant maintenance engineers, people installing TV aerials or solar panels, salespeople and school caretakers can all be at risk.

Roofs that are typically fragile include those constructed from asbestos cement sheets, and those with rooflights.

Hopefully, no one managing work at height would allow workers onto a fully glazed roof as was the case with the labourers on the roof of London's Crystal Palace in the 1920s in our main illustration (right). But the HSE says any roof should be treated as fragile unless a competent person has confirmed it isn't.

Even roofs which were non-fragile when they were installed can deteriorate and become fragile over time as a result of ageing, lack of maintenance, impact, thermal stress, and damage from rain and storm water. All of which means it's safest to assume any roof surface is fragile, unless you are certain it isn't.

Any work on a fragile roof should be recognised as highly dangerous - even a simple inspection or a quick repair - and, because it is high-risk work, it should not be undertaken alone. But accidents can be avoided if suitable equipment is used, and if those carrying out the work are given adequate information, instruction, training and supervision.

Stay away

"Following the hierarchy set out in the Work at Height Regulations 2005 is the key to working safely on fragile roofs," says Sarah Hague of the HSE's Construction Group.

This hierarchy applies to any work at height, including roofs, and follows the usual order of controls for any risk.

• Avoid work at height where you can.
• Use equipment to prevent falls where you cannot avoid it.
• Use equipment to minimise the distance and consequences of a fall where you cannot eliminate the risk.
• Always consider collective protection measures (such as scaffolds, nets, soft-landing systems) before measures that only protect the individual, such as harnesses.
• Ensure that work is carried out only when weather conditions do not
  jeopardise the health and safety of workers - don't work in rain, or freezing or windy conditions.

Hague's advice on roof work is: "Think hard about why you are going up onto the roof and whether you really need to. Is it just to carry out cleaning for cosmetic purposes? If it is, then don't do it ..." For inspections, you may be able to look out of the window of an adjacent building, using binoculars if necessary, or use remote camera equipment.

"If the work absolutely has to be done, for example there is a leak, then carry out a risk assessment and use the hierarchy to plan and manage the work, and ensure that people have the right knowledge, training and equipment to do the job, and that they know how to use the equipment properly."

A little lift

The HSE says that all work should be carried out from beneath where practicable but, where this is not possible, it advises considering using a mobile elevating work platform (MEWP).

MEWPs, such as scissor lifts, can provide both edge protection and a working platform which makes them ideal for jobs such as replacing small numbers of
roof sheets.

Mobile platforms bring their own risks of course, and Hague says it is essential that you have the right equipment for the job, such as all-terrain lifts.

"Look at the ground conditions, and check whether there are holes or obstacles. There could be a risk of the equipment overturning," she advises.

Anyone using access equipment will need training. Only qualified and competent operators should drive the equipment.

According to Rupert Douglas-Jones, international training manager at the International Powered Access Federation (IPAF), on-site familiarisation is equally important because makes and models differ. Operatives need to know, for example, how to use the emergency lowering system on a particular piece of equipment.

"The key message with a MEWP is once you are in the basket, don't get out," says Hague. "Be aware of structures around you, as collision with them can result in potentially fatal crush injuries."

Workers inside a basket need to wear harnesses and a work restraint lanyard system attached to a secure fixing and anchorage. IPAF and the Construction Plant Hire Association (CPA) are campaigning jointly to have every boom in the country displaying a "Clunk-click" sticker, reminding workers that just as they need to put on a seat belt when they get in a car, they need to wear a harness in the basket of a boom.

Tread carefully

If you can't avoid sending workers onto a potentially fragile roof, there must be safe access onto the roof surface using general access scaffolding, a tower scaffold or a MEWP again.

But Douglas-Jones warns that only in very rare cases will the safest way of doing a job involve exiting the work platform at height. In such cases, the access gate should face away from the edge of the structure, and there should always be a vertical gap of at least 120mm between the work platform and the adjacent structure to prevent a limb being trapped as the weight of the passenger is transferred and the platform moves.

The British Standard for use of MEWPS, BS 8460, says the risks that need assessing before anyone exits a platform at height to another structure such as a roof include:

• the possibility of people or tools falling during transfer from the platform to the structure
• damage to the structure by unintentional movement of the platform
  the chance of people becoming stranded at height.

Space constraints may mean that ladders have to be used for access, but these should always be seen as a last resort and, where they are used, they should be tied off securely (see Rung out?).

You must always provide a safe way of moving across the roof, using proprietary staging (also known as crawl boards) or purpose-made roof ladders.

The roof perimeter should be fitted with edge protection (guard rails and toe boards - see Right on the edge); a proprietary access system; and measures to prevent falls through particularly fragile parts, such as skylights (this means providing barriers or covers), and to mitigate the consequences of any fall.

Working platforms or staging should span at least two purlins (roof supports that cross the main rafters) to provide adequate support across roof members and spread the load.

The HSE says that unless all the work and access is carried out on stagings or platforms fitted with guard rails, safety nets should be installed under the roof, or workers should use a harness system.

Nets or any other fall-arrest system must be designed properly and installed by competent people. Hague says it's important to ask net riggers "Have you got your ticket?" to check they have the CSCS (Construction Skills Certification Scheme) Safety Net Rigger card, which is the safety netting competence card for the construction industry.

When using personal fall protection systems (safety harnesses), Hague says workers must be trained in how to choose the correct kit.

"It's important they know which is the right kind of equipment for the job - for example, whether to use a short lanyard or a longer lanyard in work restraint or fall arrest. They need to know how to wear a harness, and how to adjust it.

 "They also need to know about how to check for damage, what to do if equipment is damaged, how to connect the equipment to suitable anchorage points, and rescue procedures."

For detailed advice on best practice for working on fragile roofs the best concise source is the Advisory Committee for Roofwork's (ACR's) Green Book - Fragile Roof Guide, ACR Best Practice Guide (ACR [CP] 002:2005).

The HSE is revising its guidance on roofwork and new versions of the priced publication Health and Safety in Roof Work (HSG 33) and the free leaflet Working on Roofs (INDG 284) will be available later this year (the old versions have been withdrawn in the interim).

In the meantime, the HSE's Health and Safety in Construction (HSG 150, available from www.hsebooks.com, priced £10.95) contains advice on
working at height, including work on fragile roofs.

Managing Health and Safety in Construction: Construction (Design and Management) Regulations 2007 Approved Code of Practice (L 144, £15) provides guidance on competence and training, including how to assess the competence of organisations and individuals.