Demarcation system.
Using D-marc™ 105 m we can provide a demarcation system for flat rooftops. Applications may be for the purpose of preventing access to hazards during regular rooftop maintenance or to provide safe access across the roof.
D-marc™ 105 has been wind tunnel tested on single ply, bituminous and concrete roof surfaces resisting wind speeds in excess of 105 mph.
Installation
The system requires no specific training to install, the upright is slotted into the base and the chain is then placed on the hook on the upright and linked to the next section of chain with the chain link supplied.
There are no specific components for corners or curves, the system can follow the demarcation zone as indicated with the posts being placed at 3 m intervals.
Installers should ensure that the system is placed at least 2 m from any fall hazard and whilst being installed ensure that they are following the practices laid down by the The Work at Height (Amendment) Regulations 2007.
The base weights are designed with a carrying handle and weigh less than 12.5 kg each.
Legislation
D-marc™ 105 is classified as a form of Collective 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 illustrate 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 not less than 2mtr).
Health and Safety in Roof-work 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 2mtr), e.g. work on an air-conditioning unit in the middle of a roof.”
Traditional Systems and Wind Uplift
Traditional demarcation systems on rooftop applications suffer from instability and wind uplift causing them to fly off roofs at wind speeds as low as 50 mph. Guidance on whether your building will be vulnerable to such wind speeds can be taken from two areas:
BS6399-2: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 50 mph, 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 10 years there have been 77 such events.
D-marc™ 105 The Wind Resistant Demarcation System.
The D-marc™ 105 can withstand wind speeds of up to 105 mph due to the unique design of its base and upright which also eliminates any potential damage caused by oscillating.
The Upright
The lattice structure ensures the wind circulates around and through the system rather than pushing it over. It’s 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 Base:
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.
