Why is a peel stop bar important on a fully adhered single ply roof?

What is a peel stop bar?

A peel stop bar, sometimes known as a 'termination bar', is a metal bar normally manufactured from either steel or aluminium, and generally pre-punched at regular intervals to accommodate fasteners. They are normally used on flat roofs with single ply membrane which has been adhered - fixed around the perimeter and around any large penetrations such as rooflights to prevent the membrane from lifting or 'peeling' due to wind uplift.

Whilst there are other ways of securing the perimeter, a peel stop bar provides an even distribution of load.

Why are they important?

The corners and the perimeter of any flat roof are subject to the greatest wind loads. If the wind gets into the roofing system, it will likely start to lift. Once it has started, it then tends to continue to lift - often resulting in losing either all or at least a significant part of the roof.

Reasons why they're important include:

1. A peel stop bar provides a mechanical anchor, preventing the membrane from lifting and potentially separating from the underlying insulation or decking.

2. Thermal expansion and contraction - temperature fluctuations can cause the roofing membrane to expand and contract. A peel stop bar helps to accommodate this movement, reducing the risk of tearing or delamination.

3. Parapet wall protection - parapet walls are particularly vulnerable to wind uplift and water penetration. A peel stop bar installed along the parapet edge provides a strong mechanical connection between the membrane and the wall, preventing the membrane from peeling away and exposing the roof to the elements.

How are peel stop bars installed?

The waterproofing manufacturer will generally provide guidance on where and how they should be fixed - as well as specify fixing centres (typically between 200-250mm). Most bars are pre-punched to suit tube washers and through fixings - and if insulation is present, using tube washers prevents cold bridging.

The bars should then be fastened through any insulation and into the structural deck or the parapet upstand.

Fasteners fit for purpose should be selected paying care to any minimum embedment or penetrations as set out in industry standards such as the SPRA Design Guide, etc.

Finally, the peel stop bar would normally be covered with membrane to prevent any water ingress into the roofing system.

How environmentally friendly are they?

Peel stop bars are intended to last the lifespan of the building or roof application they are used within. They aren't replaceable, but being mechanically fastened means they can be deconstructed at the end of a project for recycling.

If you require specific details on the environmental credentials of these products, your chosen manufacturer should be able to provide this information.

Refer to SPRA Design Guide, section 3.16.3 & section 5.10.2 for more information