Fragile roofs and rooflights: the building owner's duties
Updated 23 October 2026 · SEO Dons Editorial
Check your re-roof against the rules ↓
What makes a roof or rooflight fragile?
The Work at Height Regulations 2005 define a fragile surface as one "which would be liable to fail if any reasonably foreseeable loading were to be applied to it". HSE starts from caution: all roofs, once fixed, should be treated as fragile until a competent person has confirmed that they are non-fragile. It lists these as likely to be fragile.
| HSE's list | HSE's qualifier |
|---|---|
| Fibre-cement sheets | Non-reinforced, whatever the profile |
| Rooflights | Particularly those in the roof plane, hard to see in some light or hidden by paint |
| Liner panels | On built-up sheeted roofs |
| Metal sheets | Where corroded |
| Glass | Including wired glass |
| Chipboard or similar | Where rotted |
| Others | Including wood wool slabs, slates and tiles |
HSG33, HSE's roof work guidance, adds two points for flat and low-pitch commercial roofs. A corroded metal sheet is likely to be fragile as the deck under a membrane, not only as the visible covering. And wood wool slabs should be treated as fragile if under 75 mm thick without nylon net reinforcement, under 50 mm thick with it, or wet or previously damaged. HSE says falls through fragile materials, such as roof lights and asbestos cement roofing sheets, account for more roof work deaths than any other single cause. Asbestos cement sheeting brings a second hazard, covered in the asbestos cement roof guide.
Why does a roof that was safe to walk on become fragile?
Non-fragility does not last. HSG33 says all non-fragile roofs will deteriorate with time and at some point the assembly will become fragile. It flags three things that hide the change: past repairs, especially where fragile sheets were used to patch an otherwise non-fragile roof; rooflights painted to reduce glare, which makes them difficult to identify; and insulation applied externally to a load-bearing roof that still contains fragile rooflights, which can obscure them.
An old drawing, or a certificate for the original roof, therefore says little about what the roof carries today. The Advisory Committee for Roofsafety (ACR) gives the safe default: if there are any doubts, assume that the roof is fragile.
What does regulation 9 require, and does it reach the owner?
Regulation 9 works in three steps, each a duty on the employer.
- Keep people off. No person at work passes across or near, or works on, from or near, a fragile surface where the work can reasonably practicably be done safely without it.
- Protect those who must go. Otherwise suitable and sufficient platforms, coverings, guard rails or similar means of support or protection must be provided and used, so far as is reasonably practicable. If a risk of falling remains, the employer must minimise the distances and consequences of a fall.
- Warn. Prominent warning notices go at the approach to the fragile surface, so far as is reasonably practicable. Where that is not practicable, people must be made aware of it by other means.
Regulation 3 applies the employer's duties to work by "any other person under his control, to the extent of his control". HSE says that if you control work at height, for example "facilities managers or building owners who may contract others to work at height", the Regulations apply to you.
The contractor holds the detailed duty to plan the work and protect its people. How far an owner's own duties reach is a question of fact. An owner that decides who goes on the roof, when and by what route is more likely to find them reaching it than one that hands a defined job to a competent contractor and supplies the facts it needs. The work at height checklist covers the wider duties.
What must an owner tell contractors about fragile areas?
Say it in writing before the contractor prices the job. HSE's leaflet for building owners and occupiers, GEIS5, tells owners to ensure that a competent person assesses the roof using a safe system of work, to specify non-fragile assemblies for new and replacement roofs, and to satisfy themselves that the contractors have allowed sufficient time to do the work safely.
The facts belong in the pre-construction information a client gives every designer and contractor appointed or being considered, as the pre-construction information guide explains. HSG33's examples include the roof's condition, including its structure, covering and rainwater goods, and any permit-to-work arrangements the client operates. For fragile surfaces, add:
- where every rooflight, light band, hatch and former opening is, including any hidden by paint, insulation or later membrane layers;
- whether the deck has been patched, repaired or has corroded;
- the roof's asbestos register entries, because HSE says the dutyholder must provide information on the location and condition of asbestos-containing materials to anyone who may work on or disturb them;
- any covers, nets, signs or marked areas already in place, and who maintains them.
Where anything applied to a roof may disguise fragile parts, HSG33 says to mark them clearly, record that information, and erect warning notices at all access points.
How is a roof or rooflight made non-fragile?
1. Use an assembly that has passed the ACR test
The ACR's Red Book, ACR(M)001-2019, is a test standard for any product that will form a roof or part of one. It is intended to show whether the assembly can support the instantaneous loads imposed by a person stumbling or falling on it. The ACR lists the sixth edition, published on 31 December 2019 and amended in May 2020, as the latest. Assemblies tested by a competent person may be classified as non-fragile Class A, B or C, and one that fails must be classified as fragile. HSG33 asks for Class C as a minimum on low-maintenance roofs and Class B on medium-maintenance roofs. The ACR describes the test as the UK's only one recognised by HSE for the non-fragility status of roofing products.
Glass needs separate care: the Red Book warns that glass may pass the soft body impact test yet is particularly susceptible to hard body impacts the test does not include. Replacement is covered in the rooflight replacement guide.
2. Protect the fragile parts already there
HSE says protection must be provided at fragile rooflights, "either by using barriers or covers that are secured and labelled with a warning". GEIS5 adds that proprietary covers can serve as either a temporary or a permanent installation, and shows safety netting protecting roof lights during minor works. A cover protects a person who falls against it. It does not change how the rooflight beneath would be classified.
3. Avoid the roof altogether
GEIS5's first choice is to avoid workers having to go on the roof at all, by adapting a method that allows profiled roof sheets or roof lights to be replaced from underneath using a suitable work platform. Where topside access cannot be avoided, it points to a mobile elevating work platform that lets people work from within the basket.
What should warning signs on a fragile roof do?
Regulation 9(3) asks for prominent warning notices at the approach to the fragile surface. HSG33 adds three points.
- Durability. Signs should be durable, securely fastened and properly maintained, and meet the Health and Safety (Safety Signs and Signals) Regulations 1996. HSE describes a warning sign as triangular, with a black picture on a background at least 50% yellow.
- Placement. Its method statement checklist includes displaying warning signs on existing roofs, particularly at roof access points, and HSE's guidance on falls through fragile roofs gives the same advice.
- Limits. Signs warn of dangers on existing buildings, including where the roof's load-bearing properties are classed as fragile or are unclear because of ageing. They are not an alternative to a designer's duty to design out hazards at source.
A sign is not the first control. HSE's order for fragile surfaces starts with avoidance, moves to stagings, guard rails, fall restraint, fall arrest and nets, and only then adds communication. A sign does not make a rooflight safe to lean on, and it does not replace a method statement. If you want to talk a roof through with a contractor, you can send an enquiry through the form on this site, and the commercial flat roof repair guide sets out what a repair should involve.
Sources
- Work at Height Regulations 2005: regulation 2, regulation 3, regulation 9, legislation.gov.uk, checked 22 October 2026
- CDM 2015 regulation 4 and Health and Safety at Work etc. Act 1974 section 4, legislation.gov.uk, checked 22 October 2026
- HSE: Fragile surfaces, Roof work, Work at height: the law, Falls through fragile roofs, Safety signs, Duty to manage asbestos, checked 22 October 2026
- HSE: HSG33 Health and safety in roof work (PDF) and GEIS5 Fragile roofs (PDF), checked 22 October 2026
- Advisory Committee for Roofsafety: Red Book, IS3, home page, checked 22 October 2026
Common questions
Is a flat roof with a waterproof membrane fragile?
It can be. A membrane does not make a roof non-fragile, because the legal test is what the surface would do under a reasonably foreseeable load. HSE says to treat all fixed roofs as fragile until a competent person confirms otherwise, and lists corroded metal decks and thin or damaged wood wool slabs as likely to be fragile whatever sits on top.
Who is responsible for fragile rooflights on a let industrial unit?
Section 4 of the Health and Safety at Work etc. Act 1974 puts a duty on each person who has, to any extent, control of non-domestic premises used as a place of work or of the means of access to them. A person with a contract or tenancy obligation to maintain or repair is treated as having control of the matters it covers. That can be the landlord, the tenant or both, depending on the lease. This is general information, not legal advice.
Does a rooflight cover remove the need for a safe system of work?
No. GEIS5 says safe systems of work must be planned and followed to protect those installing the safety measures. HSE's roof work page also describes a method statement as the common way to manage roof work and communicate the precautions to those involved.
What if nobody is sure whether a rooflight is fragile?
Assume it is. The ACR says that if there are any doubts the roof should be assumed fragile. HSG33 adds that where an industrial roof's condition is in any way suspect, nobody should walk on it to survey it, and the inspection should be made remotely from the ground or from a mobile elevating work platform.
Related guides
Check your re-roof against the rules
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