Mobile Anchor Weights on Flat Roofs: Function, Selection, and What Matters
Mobile counterweights are at the heart of most temporary fall protection systems on flat roofs. Without them, no freestanding guardrail is secure. Nevertheless, they are often treated as an afterthought in purchasing decisions.
Why Counterweights Are Necessary
A freestanding guardrail on a flat roof cannot be attached to the building – the roof waterproofing must not be damaged, and often there are no suitable anchor points. The system must therefore be stable in its own right. The only force that makes this possible is weight. The DIN EN 13374 Class A standard defines the forces a guardrail system must withstand – and thus also how much ballast is required at which point.
What Counterweights Must Do
Not every concrete block with a hole in the middle is a suitable counterweight. Reputable systems come with weights that are positively engaged in the system upright, have a defined mass (typically: 20–30 kg per element), are stackable and manageable, have no sharp edges that could damage the roof membrane, and are made of weather-resistant material.
Manufacturers like Euroscaffold specify exactly how many weight units per upright are needed for a given upright spacing and wind load zone. This information is not marketing – it is the basis for the system to retain its approval.
Wind Load: The Underestimated Factor
The most common cause of insufficient ballast is an incorrect assessment of the wind load. Germany is divided into wind zones – coastal areas and exposed locations require significantly more ballast than wind-protected city center roofs. In addition, there is the installation height: More wind acts on a 20-meter building than on the ground floor.
Roof Membrane Protection: Often Forgotten, Always Important
Concrete weights are heavy and hard. On a roof waterproofing made of bitumen or plastic membranes, they can cause damage – especially if they slip minimally under load or if there are pebbles under them. Good system weights therefore have a rubber underside or are placed on rubber mats.
How Much Ballast Do I Specifically Need?
There is no general answer – it depends on the system, upright spacing, wind zone, and installation height. The manufacturer's assembly instructions provide binding tables. As a rule of thumb: A guardrail on an exposed roof in wind zone 2 with 2-meter upright spacing typically requires 60–90 kg of ballast per upright.
System Compatibility
Counterweights are not universal accessories. They are matched to the respective system frame. Anyone who uses weights from another manufacturer leaves the certified system network and may be liable themselves in the event of damage. This also applies to self-made counterweights from concrete blocks or sandbags.
Counterweights at Gerüstexpress
At Gerüstexpress, roof edge protection systems including suitable accessories are offered. For questions about the correct ballasting, the team is available via the contact page.
Frequently Asked Questions
Can I use counterweights from another manufacturer?
Only if the system manufacturer explicitly allows it. Otherwise, you leave the certified system network.
How do you store counterweights correctly?
Dry, frost-protected, and in such a way that they do not fall over. Cracks or chipped corners should be checked before the next use.
Do counterweights need to be inspected?
There is no formal inspection requirement for the weights themselves. However, the obligation to check the entire system for correct execution after assembly exists – this also includes the correct number of ballast elements.
