Template:ROOFTOP GARDENS, PLANTERS & WALKWAYS (EPDM, TPO)

1 General

Thermoset and Thermo Plastic (EPDM, TPO, PVC) single ply membranes used for Landscaped and Vegetated roofing systems shall be fully adhered and a minimum thickness of 1.5mm (0.060"). 

Membrane Protection: Protection for roofing membranes is required during the installation and maintenance of landscaping, extensive and intensive vegetated (green) roofing installations. The minimum membrane protection must be installed by the roofing or waterproofing contractor and shall be 3 mm (1/8") asphalt core protection board or 25 mm (1") minimum extruded polystyrene insulation plus filter mat, root intrusion barrier, and drainage layer. Tightly butt all protection and insulation boards, overlap all filter mat seams and seal all laps of roof intrusion barriers to RGC Guarantee Standards and manufacturer’s installation instructions.

Only RGC accepted Thermoset roofing membranes that are specifically accepted by the membrane manufacturer for use on Landscaped and Vegetated (green) roof systems qualify for coverage under the RGC Guarantee Program. The Membrane Manufacturer and RGC must confirm acceptance of other alternative protection systems or components in writing. Damage to membranes and flashings that results from the use of plants with aggressive root structures, (Bamboo, Willow etc.) for landscaped and green (vegetated) roof systems, is specifically not covered under the RGC Guarantee Program or the responsibility of RGC. For additional information refer to the latest addition of the British Columbia Landscape Standard, Green Roof Section.

2 Root Barriers & Drainage

Proprietary root intrusion barriers must be acceptable to the roof membrane manufacturer and appropriate for the vegetation system installed. Polyethylene or polypropylene sheeting used as a root barrier shall be a minimum thickness of .2mm (8mils). Root Barriers shall be sheets or boards installed in a continuous plane above the roof membrane, carried up the inside of soil retention perimeters (separation zones), and must be installed with sealed laps and seams as per manufacturer's instructions.

A drainage layer is required. Specialized proprietary drainage products must be acceptable to the membrane manufacturer.

Separation Zones that are free of growing medium and vegetation are required around all roof perimeters, up-stands, drains, penetrations, mechanical equipment, expansion joints, etc. Zones must be a minimum of 300 mm (12”) wide and constructed with curbs or other physical barriers that separate and facilitate drainage. Physical barriers must be placed above the membrane protection layers and must not be attached through or penetrate the roof membrane.

3 Planter Design & Waterproofing

Non-structural planters placed over landscaped deck and roofing membranes, with an appropriate protection layer, are strongly recommended whenever practical.

4 Flood Testing

Flood Testing is not a recommended practice but is at the discretion of the design authority or owner on systems permitted by ASTM D5957. If flood testing is required, testing shall be conducted prior to installation of overlying insulation or overburdens and conducted as per ASTM D5957.

5 Overburdens

In the case of Extensive Green Roofs (roof top gardens) with soil thickness of 200 mm (8") or less, when the landscaping (soil and plants) is included as part of the roofing specification and / or contract, the costs for removal and replacement of soil to access the membrane, to investigate or repair leaks in the membrane, are included in the RGC Guarantee coverage. Extensive Green Roofs may be constructed with coarse aggregate or be specialized proprietary drainage panels, vegetation trays and/or mats designed to direct excess water to roof drains. However, the removal and replacement of plants, irrigation lines and or equipment, electrical lines, landscape and decorative features such as concrete pads, statues, planters, large rocks, etc., to investigate or repair leaks in the membrane, is not included, and is the responsibility of others, subsequently such access shall be provided and or paid for by others.

In the case of Intensive Green Roofs (roof top gardens), and Landscaped Roofs with soil thickness in excess of 200 mm (8"), where access to the roofing membrane may be difficult, the removal and replacement of soil and plants to access the membrane to investigate or repair leaks in the membrane is the responsibility of others, and such access shall be paid by others. In addition, the removal and replacement of plants, irrigation lines or equipment, electrical lines, landscape and decorative features such as concrete pads, statues, planters, large rocks, etc., to investigate or repair leaks in the membrane is also the responsibility of others, and such access shall be provided and or paid for by others.

Structural planters that incorporate pre-curb or start-up curbs for walls that are completely sealed with membrane and are a minimum of 100 mm (4") in height, as detailed in Section 5 & 9 Construction Drawings, qualify for RGC Guarantee coverage. Waterproofing liners in planters with structural walls, concrete curb or other materials, that do not incorporate pre-curbs shall be isolated and separated from the guaranteed roofing membrane and are specifically not accepted under the RGC guarantee.

6 Walkways and Warning Zones

When primary roof membranes of contrasting colour are used for warning zones, membrane end lap off sets and ply side lap directions must be maintained. Staggered membrane end lap offsets may be positioned below primary roof membranes that are used for warning zones.

A design authority or membrane manufacturer may specify a proprietary walkway protection system or warning zone membrane over the primary roof membrane. Walkway and warning zone materials are not part of the roofing membrane assembly but are typically accessory products that are placed over completed roof membranes. Subsequently the type and performance of any walkway or warning zone material is specifically excluded from coverage under the RGC guarantee, as is any detrimental effect the materials may have on the roof system.