When considering single-ply membranes for a roofing application many things need to be taken into account: is the roof an exposed application? Is it a ballasted or green roof? Is it heavily trafficked or even a situation where the aesthetics are the most important factor? Steve Hatcher, SPM Field Technican at Sika, discusses choosing the right membrane and roofing system for the right application and how it is the first most important step. Within Sika-Trocal there are different membrane types to suit all of these applications, but it is important to choose the right one as the substrate can also determine the type of roof system.


Secondly, Sika-Trocal has a network of licensed contractors that have been trained at our academy. Sign-off inspections take place on site before guarantees are issued, reassuring clients that the products are being installed correctly and by trained labour.

Select for success

Choosing the correct single-ply membrane also depends on a number of factors. A mechanically-fastened system may be used on a large roof area for speed of installation such as the Sika-Trocal Type ‘S’ system, where fasteners restrain both the membrane and the insulation in a single fix. If an application has a concrete substrate then an adhered membrane such as Sika-Trocal Type SGK could be used to limit the amount of mechanical fastening into the concrete.


It may be a feature roof such as a barrel-style roof, again where adhered Sika-Trocal type SGK could be used where the aesthetics of the roofing system are very important. Ballasted or green roofs - as stated - have their own dedicated membrane in the Sika range with Sika-Trocal type SGmA.


Once the membrane is installed it is then time to seal the laps to make it watertight. This is normally achieved through heat welding with most single-ply systems, but with Sika-Trocal membranes this also is usually carried out with solvent welding, making the process much quicker and more efficient. In all situations, a wind uplift calculation will need to be carried out to determine the number of fasteners required, or to establish if it is safe to install an adhered system. Sika-Trocal licensed contractors can log into the Sika-Trocal web-based programme where they can generate their own wind uplift calculations, all in accordance with the latest European codes of practice.

Good outlets

Sika-Trocal single-ply membranes, especially the mechanically-fastened type S system, will use membrane-laminated profile metals at all perimeters and change of angles within the roofing system to restrain the membrane. Again, these should be designed in accordance with BS 6229, therefore at upstand junctions the minimum height should be 150mm above finish roof surface.


Once the main roof is complete, the outlets and any penetrations can be completed. Roof outlets will normally be supplied in rigid PVC so the membrane can be fully-welded to these in the same way as the laps of the membrane, creating a watertight seal. Penetrations can also be detailed using rigid PVC units or Sika-Trocal laminated metals formed to suit the size and shape of the detail. Standard UPVC pipes such as SVP pipes can be detailed using single-ply membrane and fully-welded to ensure they are watertight. Any services or freestanding plant that is to be located on the roof surface will need sacrificial protection layers installed to ensure the roofing membrane is protected and to ensure there are no issues with compatibility with the support feet and pads of the units and the roofing membrane itself.

The final step

To complete the roof, it may be required to install a slip-resistant walkway in order to protect the roofing system or keep foot traffic to a safe area of the roof. These can be fully-welded to the roofing systems, using various thicknesses such as Sika-Trocal WBP20 or the HD walkway for more frequent foot traffic. Further items such as lightning conductor systems are available using semi-rigid PVC pads that simply weld down to the roofing sheets at the required centres, making a very quick and simple method of attachment. Fall arrest systems are also manufactured using PVC coated units in order to be fully-sealed to the roofing membranes, again providing an easy application.


Single-ply membranes are increasingly seen as a simple, modern solution for the watertight protection of a range of roofing applications. However, nothing should be taken for granted when it comes to their installation in order to guarantee long-term performance. Hopefully, this guide helps highlight a number of seemingly smaller details which should be fully-addressed to ensure a single-ply membrane lives-up to its billing as the quality, roofing solution for today and years to come.