Treat every roof and rooflight as fragile until a competent person has confirmed it is not, then plan the job so nobody has to go on it. If someone must, the Work at Height Regulations 2005 require platforms, coverings or guard rails that carry their weight or keep them off the fragile material, measures to limit any fall that remains, and warning notices at the approach. You cannot judge fragility by eye: rooflights get painted over, hidden by moss and dirt and weakened by sunlight, and “it held last time” proves nothing.
At a glance: Nexis CPD offers a £9 CPD-accredited online Working at Height Awareness course — 100% online, with an instantly emailed, employer-verifiable certificate. Any three courses cost £18. This article is general information, not legal advice.
What is a fragile roof?
The legal test is about load, not material. Regulation 2 of the Work at Height Regulations 2005 defines a fragile surface as “a surface which would be liable to fail if any reasonably foreseeable loading were to be applied to it”. HSE’s fragile surfaces guidance puts it practically: fragile materials will not safely support the weight of a person and any materials they are carrying.
That means more than someone standing still. HSE’s Health and safety in roof work (HSG33), now in its fifth edition (2020), warns that some coverings carry a spread load well enough to look safe, then fail “like a trap door” under a concentrated one, such as a walking heel or a person stumbling and falling. Asbestos cement and other non-reinforced fibre cement sheets can shatter without warning and become more brittle with age.
How can you tell if a roof is fragile?
Usually you cannot, which is why HSE says all roofs, once fixed, should be treated as fragile until a competent person has confirmed they are non-fragile. HSG33 lists what disguises fragile material:
- rooflights obscured by paint, debris or vegetation, or weathered to match the rest of the roof;
- rooflights painted to reduce glare, or hidden under insulation applied over the roof;
- old repairs where fragile sheets were used to patch a non-fragile roof, which HSG33 calls highly dangerous;
- corroded metal sheets and water-damaged wood wool slabs;
- red screw or bolt caps used to mark rooflights, which can bleach with age.
HSE also notes that some rooflights are difficult to see in certain light conditions.
Do not walk on a roof to find out. HSG33 says that where an industrial roof’s condition is in any way suspect, nobody should walk on it to survey it: inspect remotely from the ground, or from a mobile elevating work platform (MEWP) or another safe means of approach. The building’s health and safety file, past survey reports and the asbestos register all help, and rooflights that are hard to spot from above are often obvious from inside, although painted-over ones may not be.
Which roofing materials are fragile?
HSE says the following are likely to be fragile, and that the list is not exhaustive. The table draws on HSG33, HSE’s fragile surfaces page and HSE’s farming guidance.
| Material | Why it can fail | Where you typically find it |
|---|---|---|
| Old rooflights, including plastic sheets matching the roof profile | Degrade with sunlight and age, discolour, and are often painted, dirty or hard to see | Factories, warehouses, farm buildings, older commercial units |
| Non-reinforced fibre cement sheets, including asbestos cement | Brittle and can shatter under a stumble; HSG33 says even reinforced fibre cement should still be treated as fragile | Older industrial, agricultural and garage roofs |
| Old liner panels on built-up sheeted roofs | Not designed to be walked on as a single layer; exposed when outer sheets are removed | Refurbishment of insulated industrial roofs |
| Corroded metal sheets | Corrosion of the sheet, fixings and washers, whether as the outer covering or the deck under a membrane | Ageing industrial roofs and flat roof decks |
| Glass, including wired glass | Breaks under a person’s weight and can drop shards on people below | Glasshouses, roof glazing and atria |
| Rotted chipboard and strawboard | Loses strength when wet, often hidden under felt or membrane | Flat roof decks |
| Wood wool slabs | HSG33 says treat as fragile if under 75 mm thick without nylon net reinforcement, under 50 mm with it, or wet or damaged | Flat roof decks on older buildings |
| Some slates, tiles and timber battens | Break or give way underfoot; battens deteriorate with age | Pitched roofs |
| Unfixed or partly fixed sheets | HSG33 says these make the roof assembly fragile until fully fixed | New roofs and re-roofing in progress |
What does the law say about working on fragile surfaces?
Regulation 9 of the Work at Height Regulations 2005 sets a specific duty for fragile surfaces in three steps:
- Avoid (9(1)). Employers must ensure nobody at work passes across or near, or works on, from or near, a fragile surface where the work can reasonably practicably be done safely, and under appropriate ergonomic conditions, without doing so.
- Support or protect, then minimise (9(2)). Otherwise, suitable and sufficient platforms, coverings, guard rails or similar must be provided and used, so far as reasonably practicable, so that any foreseeable loading is supported or borne by them. If a risk of falling remains, the distance and consequences of a fall must be minimised.
- Warn (9(3)). Prominent warning notices must, so far as reasonably practicable, be fixed at the approach to the fragile surface; otherwise people must be made aware of it by other means. Regulation 9(4) disapplies this warning duty for the emergency services acting in an emergency.
Regulation 3 extends these duties to relevant self-employed people and to anyone controlling other people’s work, to the extent of their control. Regulation 4 requires work at height to be properly planned, including for emergencies and rescue, appropriately supervised, and done only in weather that does not endanger people. Regulation 9 follows the avoid, prevent, minimise order explained in our guide to the hierarchy of control for work at height, and our overview of the Work at Height Regulations 2005 covers the rest.
Roof repair, maintenance and high-pressure cleaning are also construction work under CDM 2015, so client and contractor duties apply, plus principal designer and principal contractor duties where more than one contractor is involved. CDM regulation 9 requires designers to eliminate, so far as reasonably practicable, foreseeable risks to people who will maintain or clean the structure, which is where fragile rooflights should be designed out. See our guide to the CDM Regulations 2015. Northern Ireland has its own work at height regulations.
How many people are killed falling through fragile roofs?
HSE’s figures vary between publications and its web pages do not say which period they cover, so treat them as indicators rather than one current statistic:
- HSE’s fragile surfaces page (last updated October 2024) says falls through fragile surfaces, particularly fibre-cement roofs and rooflights, account for 22% of all fall-from-height fatal injuries in construction.
- HSG33 (2020) says roof work accounts for a quarter of all construction deaths, and that falls through fragile materials such as rooflights and asbestos cement sheets cause more of those deaths than any other single cause. HSE’s roof work page (updated June 2026) says almost one in five.
- HSE’s 2012 leaflet Fragile roofs (GEIS5) said an average of seven people a year were killed falling through fragile roofs or rooflights, usually on factories, warehouses and farm buildings during repair or cleaning.
HSE’s farming guidance on falls (updated July 2024) says falls are the second highest cause of death in agriculture, with at least eight people dying from a fall from height every year, often from roofs among other places, and that most fibre cement roofs will be fragile.
Who is most at risk of falling through a fragile roof?
Mostly not specialist roofers. HSE says people doing small, short-term maintenance and cleaning jobs are over-represented in the injury statistics, and HSG33 says many people killed or injured on roofs are carrying out other tasks, such as maintenance and surveying. They include:
- maintenance staff fixing leaks, servicing roof plant or replacing a sheet;
- gutter cleaners, especially in valley gutters between fragile slopes. HSG33 describes a labourer who fell 9 m after stepping onto a rooflight while cleaning a gutter;
- roof cleaners. HSG33 describes a 23-year-old casual worker killed after stepping off his boards onto a rooflight while power-washing a farm building roof;
- solar panel and aerial installers, who HSG33 says need relevant training for working at height on roofs;
- farmers and farm workers repairing barns and livestock buildings;
- surveyors and inspectors checking a roof’s condition.
The common thread is a job that feels too small to plan. HSE says effective precautions are needed for all work on or near fragile surfaces, however short.
How do you avoid going on a fragile roof?
First ask whether the work is needed, then whether it can be done without anyone on the roof surface. HSE’s order for fragile roofs, in HSG33 and GEIS5, is to work from underneath using a suitable platform, and failing that from a MEWP basket without standing on the roof.
- Inspect remotely. HSG33 suggests pole-mounted cameras, commercially operated drones (provided aviation law is followed) or binoculars from an adjacent structure.
- Replace from below. Proprietary systems let damaged sheets and rooflights be replaced from a platform inside the building.
- Fix the cause. HSG33 suggests over-roofing or re-roofing with a non-fragile assembly, or replacing whole sheets, instead of repeated patch repairs.
- Design access in. Where people regularly reach roof plant or gutters, HSG33 favours permanent protection such as fixed covers over setting up temporary measures each time.
What precautions are needed if you must work on a fragile roof?
Collective protection first, personal protection last. HSG33 says that if access cannot be avoided, fit perimeter edge protection and use staging to spread the load, and unless all work and access is on staging or platforms with guard rails, install safety nets under the roof or use a harness system.
- Staging with guard rails. Platforms spanning the purlins must carry the weight of anyone on fragile material and be secured against slipping, with enough of them that workers are not constantly moving them. HSE’s farming guidance warns against leapfrogging across a roof on a pair of boards.
- Covers and guard rails. Fragile material near a route or work area must be covered or guarded so someone passing cannot fall through. GEIS5 notes that proprietary rooflight covers come as temporary or permanent installations.
- A 2 m boundary. HSG33 recommends marking safe areas with a continuous physical barrier at least 2 m from the nearest fragile material. A painted line or bunting is not acceptable.
- Safety nets. Rigged beneath and close to the roof, nets protect everyone in the area. HSG33 says riggers should be trained and competent, and a rescue plan should be in place before nets are rigged.
- Harnesses, last. HSG33 says harness systems rely on training and supervision, need anchorages of proven quality and can be ineffective below certain heights. Work restraint, which stops someone reaching the fragile material, beats fall arrest.
HSG33 calls it a “common but fatal” belief that walking the line of roof bolts over the purlins is safe: rooflights and fibre cement sheets have their weakest point of impact within 150 mm of the purlin line. Sheet overlaps are not safe to stand on either.
What should you check before anyone goes on a roof?
Drawn from the Work at Height Regulations, HSG33 and HSE’s fragile surfaces guidance. If any answer is “no” or “not sure”, nobody goes up.
- Is it necessary? Could it be done from below, from a MEWP, with a camera or not at all?
- Is fragility known? Has a competent person confirmed which parts are fragile, without walking on a suspect roof? If in doubt, treat the whole roof as fragile.
- Is the information gathered? Health and safety file, past repairs, rooflight positions including hidden ones, and the asbestos register.
- Is access safe? Scaffold, stair tower, tower or MEWP, or a properly secured ladder; see our ladder safety rules.
- Are edges protected? Eaves, gables, openings and any leading edge where sheets are removed.
- Is every fragile area within 2 m of a route or work area covered or guarded?
- Is remaining risk mitigated? Nets, or a harness system with assessed anchors and enough clearance.
- Is the weather suitable? Wind, rain, ice and low light all change the risk.
- Is there a method statement or permit? Specific to this roof and briefed to everyone.
- Are people competent and supervised? HSG33 says inexperienced workers must never work on roofs unsupervised.
- Is there a rescue plan? Equipment, people and method ready, without relying on the emergency services.
- Are approaches and the area below controlled? Warning notices, unauthorised access prevented, people kept clear below.
Do fragile roofs need warning signs?
Yes. Regulation 9(3) requires prominent warning notices at the approach to a fragile surface, so far as reasonably practicable. HSG33 says they should be durable, securely fixed, maintained and meet the Health and Safety (Safety Signs and Signals) Regulations 1996.
Signs are the minimum, not the control. HSG33 says a risk assessment is likely to require signs prohibiting access except under controlled conditions such as a permit to work, fixed ladders blocked or locked off when not needed, and disguised fragile parts marked and recorded in the health and safety file. A sign warns; only the precautions behind it make the work safe.
Can you walk on an asbestos cement roof?
No. HSG33 says asbestos cement sheet is fragile and cannot be relied on to support someone’s weight, and HSE’s farming guidance says never walk on asbestos or other fibre cement sheet. It was widely used for corrugated roofs on industrial and farm buildings and garages, as our guide to where asbestos is found explains.
These roofs carry two risks at once: falling through, and disturbing asbestos by breaking, drilling or cleaning the sheets. HSE has separate guidance on cleaning weathered asbestos cement roofs, and HSG33 says asbestos awareness training is the minimum for anyone likely to come across asbestos-containing materials. Where old sheets must come down, HSG33 prefers lowering them whole from underneath, for example from scissor lifts.
What rescue plan do you need for roof work?
A specific one, in place before work starts. Regulation 4(2) says planning includes emergencies and rescue, and HSG33 says the plan must be proportionate to the risk and not rely on the emergency services.
- Nets: how someone caught in a net is brought down, for example by ladder or MEWP. HSG33 says this is the responsibility of the principal contractor or person in control of the site, even after the riggers have left.
- Harnesses: how someone hanging on a lanyard is reached quickly. HSG33 says anyone with symptoms such as light-headedness, nausea or numbness, or who is unconscious, should be rescued as soon as safely possible, with an ambulance called for anyone who becomes unconscious in suspension.
- Falls through to the floor: who calls for help, how first aiders reach the casualty, and how the area below is kept clear.
What does “non-fragile” mean, and does it last?
The widely accepted UK test is the Advisory Committee for Roofsafety’s Red Book, ACR[M]001:2019, now in its sixth edition (amended May 2020). A sandbag of at least 45 kg is dropped from at least 1.2 m onto the roof assembly to simulate a person stumbling or falling. Class C holds it after one drop but not a second; Class B after two; Class A after two with no damage affecting weather resistance. An assembly that fails is fragile. HSG33 recommends at least Class C for low-maintenance roofs and Class B for medium-maintenance roofs.
- It is a snapshot. The Red Book says it only describes performance at the time of the test, and is not suitable for deciding whether an existing roof is fragile.
- It tests the assembly. Supporting structure, fixings, washers and sealants all count, so a non-fragile product badly fixed is not a non-fragile roof.
- Non-fragile roofs become fragile. HSG33 cites badly secured fixings, failed washers, foot-traffic damage, aggressive atmospheres and end of design life.
When specifying rooflights, HSG33 advises non-fragile rooflights, raised designs that cannot be walked on, mesh or grids beneath, and a design life matching the roof’s, allowing for UV damage. The Red Book points to National Association of Rooflight Manufacturers guidance on achieving up to 25 years’ non-fragility for GRP (glass-reinforced plastic) in-plane rooflights. HSG33 also says rooflights should not be within 2 m of valley gutters, and that test results, UV performance and fixing details belong in the health and safety file.
What training do you need to work on a fragile roof?
Enough to be competent for that roof and task, plus supervision. HSE says those doing the work must be trained, competent and instructed in the precautions, and HSG33 says inexperienced workers need formal training on roofing hazards, including fragile roofs and rooflights, before going onto a roof, working where their supervisor can see and speak to them. Erecting edge protection, rigging nets, using harnesses and operating MEWPs all need task-specific training. Awareness training helps clients, building managers and supervisors recognise the hazard and ask the right questions, but it does not make anyone competent to go on a roof.
What online training covers fragile roofs?
Nexis CPD’s Working at Height Awareness course covers the law and duties, risk assessment, the avoid, prevent, minimise hierarchy, access equipment, and managing fragile surfaces, falling objects, weather, inspection and emergency rescue. Health and Safety in Construction covers the key legal duties, including CDM, and the main site safety and health hazards. Because so many fragile roofs are asbestos cement, Asbestos Awareness (Category A) covers where asbestos is found and what to do if you find it.
£9 per course. CPD accredited, 100% online, verifiable e-certificate. Pay for 2, get 3 — any 3 courses for £18. These are CPD-accredited awareness courses. They do not qualify anyone to work on roofs, erect edge protection, rig nets or assess whether a roof is fragile, and they do not replace practical, task-specific training and supervision.
Frequently asked questions
Can you walk on a fragile roof?
Not unprotected. Regulation 9 of the Work at Height Regulations 2005 requires work to be arranged so nobody passes across, near or works on a fragile surface where reasonably practicable, and otherwise requires platforms, coverings or guard rails that support the load, plus measures to minimise any fall.
Are all rooflights fragile?
Not all, but treat them as fragile until a competent person confirms otherwise. Modern rooflights can be tested non-fragile to the ACR Red Book, but HSE lists old rooflights as likely to be fragile, and rooflights deteriorate with sunlight and age.
Is it safe to walk along the line of bolts on a roof?
No. HSE’s guidance HSG33 calls this a common but fatal belief: rooflights, asbestos cement and fibre cement sheets have their weakest point of impact within 150 mm of the purlin line, because the purlin gives an edge that can tear the sheet.
Do fragile roofs need warning signs?
Yes. Regulation 9(3) requires prominent warning notices at the approach to a fragile surface, so far as reasonably practicable, or other means of making people aware. HSE’s guidance says signs are not an alternative to designing the hazard out at source.
Is a harness enough to work on a fragile roof?
Not on its own as a first choice. HSE’s order is to avoid the roof, then use staging, guard rails, covers and nets. Harnesses come last because they rely on suitable anchors, enough clearance, training, supervision and a rescue plan.
How long does a non-fragile roof stay non-fragile?
There is no fixed period. The ACR Red Book test describes performance at the time of the test, and HSE says all non-fragile roofs deteriorate and eventually become fragile. Treat any roof as fragile until a competent person confirms its current condition.
This article is general information about working on fragile roofs and rooflights in Great Britain, not legal advice. It reflects the Work at Height Regulations 2005, CDM 2015, HSE guidance including HSG33 (fifth edition, 2020), GEIS5 and HSE’s fragile surfaces, roof work and farming pages, and the ACR Red Book (ACR[M]001:2019) as we found them on 14 October 2026; Northern Ireland has its own regulations. For a specific roof, take advice from a competent person and follow HSE’s guidance. Nexis CPD courses are CPD-accredited awareness training, not regulated qualifications, and do not make anyone competent to work on or assess a roof.