Mechanically Fixed EPDM Roofing Method
In this guide, we will demonstrate how to mechanically fix your EPDM flat roof installation. This method ensures a watertight and neat finish and offers an alternate installation method for this high performance solution. Please download the full guide in PDF format or read online using the 'Download Now' button.
It is always preferable to remove the existing waterproofing from the main part of the roof, but if you are satisfied the roof deck is in a sound structural condition, only the perimeter edge waterproofing, upstands and lose materials, e.g., felt chippings, have to be removed.
Once the remaining surface has been properly swept, the geotextile under cushion can be laid onto the roof surface. This protects the membrane from the potentially rough substrate.
At all perimeter edges and upstands, the RUSS (Reinforced Universal Securing Strip) needs to be mechanically attached to the substrate for the membrane to adhere to.
The geotextile under cushion must be secured underneath these strips using V-plates and All-purpose fasteners. It is important that each fixing into the substrate, is fixed into solid timber, i.e. joists.
The reason for this is that if the current decking is made up of chipboard, this material has no pull-out resistance. If the current deck is made up of plywood, close-boarded timber or concrete, you may fix anywhere.
Please note the fixing pattern as shown. The distance between the strips is approximately 1 metre apart, maximum. The higher the wind uplift, the closer the strips need to be. Please ask a member of Permaroof for guidance.
Once the substrate is properly prepared with the RUSS and geotextile under cushion secured, the EPDM membrane can be laid out onto the roof and positioned. Make sure enough membrane overhangs the roof perimeters and upstands, allowing it to be trimmed later.
Please note: when EPDM membrane is laid in-situ, it can take around 30minutes to relax. In cold weather conditions, this waiting time will be extended and any folds that are sometimes present in the membrane can take longer to dissipate.
The membrane is applied from the centre of the roof out towards the perimeter edges. Fold the membrane inwards to the central area, exposing the RUSS.
Clean the RUSS and underside of the EPDM sheet with Splice Wash and a cotton rag.
Once the Splice Wash quickly evaporates, Splice Adhesive can then be applied to the same surfaces.
Check the Splice Adhesive is tacky and mate the two surfaces together.
Repeat the procedure on encountering each RUSS strip. Work in one direction e.g. along the width of the roof, then apply the membrane to the strips running down the roof length.
Once the membrane is secured to all RUSS strips, the remainder of the installation can continue as described in the “Perimeter edges and upstands” section.
In addition to all perimeter edges, RUSS strip is to be installed at all round pipe penetrations larger than 125mm square and skylights.
This method of installing RUSS and Splice Adhesive must be added to fully adhered installations with a roof surface area greater than 100 square metres, but without the geotextile under cushion. The membrane will instead be fully adhered directly to the substrate.
More guides from Permaroof
Permaroof UK Ltd offers support for EPDM application, whether for trade roofers or for the DIY market. The resource library contains an extensive range of EPDM installation guides in downloadable PDF format and video tutorials with step-by-step instructions given by qualified and experienced EPDM specialists.
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