Fall number is a measure of enzyme activity; too low fall number gives sticky crust, too high gives dry crust and pale crust.

No other risk in the roofer's trade can compare to the fall. A fall from even modest height can cost mobility or life, and that is why the rules on fall protection when working on roofs are among the most concrete in all occupational health and safety legislation. They are found in the executive order on building and construction work and are explained in the Working Environment Authority's AT guidance on building and construction work (VEJ no. 10135 of 01/10/2026), chapter 7 on work on roofs. As a roofer you should know them in your sleep.

On roofs with a slope below 15 degrees, according to AT guidelines, employees who work and move on the roof must be secured against falls when there is more than 3.5 meters from the roof edge down to the surrounding substrate. The substrate can be the terrain — but also, for example, a lower flat roof on an adjacent building. If the fall height is between 2 and 3.5 meters, a written assessment of the need for safety must be made — and safety must be ensured if there is particular danger, such as slippery ground, strong wind, or work close to the edge.

• 01Over 3.5 m to the base: protection against falling is a requirement — typically railings along the roof edge.
• 022-3.5 m: written assessment of need for safety measures — and safety measures if particular danger (slippery, windy, close to edge).
• 03If work is not done closer than 2 meters to the edge, the railing may be replaced by a clear and durable marking of the work area.
• 04Holes in the roof (skylights, openings) must be secured against falling through — they are just as dangerous as the edge.

Railings and screens on construction sites must be designed according to the standard DS/EN 13374 on temporary railings — or at least at an equivalent safety level. The standard divides railings into classes based on how much load they must be able to absorb: On flat roofs and at gables, you can normally use a railing corresponding to class A with a height of at least 1 meter, while screens at the roof base on sloped roofs must be class B or C depending on roof slope and fall height, because they must be able to stop a person sliding or rolling down the roof surface.

On sloped roofs, according to the guidelines, safety against falls must always be established at the roof edge before work begins when the roof edge is more than 2.0 meters above the surrounding substrate and work is carried out at a height of more than 5.0 meters. The safety can be a scaffold and/or a barrier at least 1.0 meter high above the roof edge. If scaffolding is used, the scaffold deck must be no more than 0.5 meters below the roof edge and the scaffolding must have a handrail — often supplemented internally with a tight barrier of, for example, plywood so that a sliding person does not go through.

Occupational health and safety rules are based on a hierarchy: collective measures such as railings and screens always take precedence over personal protective equipment. Fall arrest equipment with line may only be used where collective protection cannot reasonably be established and typically only for short-term tasks. The reason is simple — a railing protects everyone on the roof all the time while a harness only protects the person who has it on correctly has anchored it properly and has a plan for how to be rescued down after a fall. If you hang in the harness for too long it is in itself life-threatening.

The employer is responsible for safety being established before work begins and on multi-company construction sites the project owner is responsible for coordinating joint measures in the safety and health plan. But in practice it is you and your colleagues who every morning check that the guardrail still stands that the marking has not blown away and that the skylights are covered. The Labour Authority can stop work and issue fines on the spot if safety is lacking — and case law shows that even work a few meters up can trigger criminal cases when safety is not in order.