Rooftop Safety Barrier

D-marc demarcation as a form of collective protection

Wherever roof access is required, designers are tasked with creating a safe route to and from the place of work. Following the hierarchy of safety collective protection measures should always be considered above individual fall protection solutions.

D-marc is classed as a form of Collective Demarcation Protection in accordance with the HSE's hierarchy of risk management as set out within the Working at Height Regulations 2005 (WAHR). The WAHR 2005 Part 3 illustrates the use of a demarcation system as an "example of taking other additional suitable and sufficient measures to prevent a fall''. The demarcation system is to be placed a safe distance from the fall hazard (normally >2m). Health and Safety Roofwork HSG33 states that "where work is not done at the edge, demarcation barriers can be provided at a safe distance from the edge (usually at least 2 metres). e.g. work on an air-conditioning unit in the middle of a roof."

Traditional demarcation systems on rooftop applications suffer from instability and wind uplift, causing them to fly off roofs at wind speeds as low as 50mph. Guidance on whether your building will be vulnerable to such wind speeds can be taken from two areas;

856399-2:Code of practice for wind loads:

The BRE confirms that buildings are generally designed for wind speeds with an annual probability of exceedance of 0.02 i.e. a 1:50 year wind speed. If your demarcation system is intended to be left on the roof for one year or more, it should meet the same design parameters.

Met Office figures:

Given that traditional demarcation systems become unstable at wind speeds of 50mph, it is worth taking a look at the likely incidence of such an occurrence in the UK. If you take a typical UK urban location e.g. Coleshill in the Midlands, figures from the Met Office show that over the past ten years there have been 77 such events.

The D-marc wind tunnel tested demarcation solution:

D-marc has been wind tunnel tested on single ply, bituminous and concrete roof surfaces, resisting wind speeds in excess of 105mph. The uprights are manufactured from a 304 stainless steel to EN I .4301. The powder coating process not only enhances lifespan, it gives a quality finish to the product. The upright section has a lattice structure which ensures the wind circulates around and through the system rather than pushing it over. Its three connecting pins do not protrude through the base and therefore do not come into contact with the roof structure. ensuring it cannot damage the roof even if it begins to oscillate. It has a non-protruding integral hook incorporated inside the lattice structure, which ensures the chain cannot lift off the upright in high winds. The plastic chain and connecting links are fully weather-proof, resistant to salt. chemicals and frost. They are also colour-fast, anti-magnetic and can be used within a temperature range of -10°C and +75°C. The trapezoid base shape is aerodynamically designed with four pyramidal sloped sides at 30° which, in extensive wind tunnel testing was shown to be the most stable shape. The underside of the base is sculpted. Ensuring the weight is distributed to its perimeter, minimising the effect of wind uplift. The base is manufactured from recycled tyres complying with BS 1790 for flammability, BS 1006 for UV stability and BS 7188 for slip resistance