Perimeters and safe access 

Perimeters

The minimum required upstand height for the waterproofing at abutments, parapets or pipe work penetrations etc, is 150mm above the completed landscape surface.

The only exceptions are:
  • At perimeter kerbs where the waterproofing extends fully to the outer edge finishing in a traditional welted drip, edge trim or at access doorways, where a linear drain is incorporated.
  • Flush threshold access doorways can normally be accommodated, and the design of the waterproofing detail at the threshold will vary dependant upon the components to be sealed to.

Vegetation Barriers

These are created with round washed pebbles or paving slabs and provide several important functions on extensive green roofs:
  • Prevent vegetation from encroaching on roof elements such as rainwater outlets.
  • Protection of the vegetation from water running down vertical upstand surfaces or from rainwater downpipes.
  • Provide rapid surface drainage during heavy rainfall.
  • Protection of the waterproofing from mechanical damage during maintenance.
  • Fire break, where the pebbles are installed in accordance with GRO guidlines of at a minimum margin of 300mm/500mm x 50mm.
  • Wind uplift resistance by increasing the imposed load at roof perimeters.

Safe Access

Provision should always be made for safe access to the roof for routine maintenance, which may include mansafe systems with harness and attachment points, internal access hatches or an externally mounted bracket to secure a ladder.

As all green roofs will need to be to be accessed at least twice a year for routine maintenance, it is a fundamental requirement of the design of the roof structure that safe access is provided for. The two important points are; safe access on to the roof by people and maintenance equipment and the safety of individuals once on the roof, ie handrail balustrades at the correct height, stable surfaces that are slip resistant etc.

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