The minimum upstand height for a single ply membrane flat roof is 150mm. This should be measured from the top of the finished roof level, and is designed to provide comprehensive waterproofing protection at abutments and around penetrations like drainage pipes.

It is critical to achieve the minimum upstand height at the same time as providing adequate falls for drainage. The roof design should therefore assess at an early the stage whether the 150mm minimum upstand can be achieved at the ‘high point’ of the roof.

Can the minimum upstand height for a flat roof be reduced?

The need to provide level access between the building interior and roof terraces or balconies has led to the development of details for a reduced 75mm upstand at the door opening. These details are available in BS 6229:2018 and the Single Ply Roofing Association (SPRA) design guide.

For a reduced upstand height at a door opening to be acceptable, certain conditions need to be met. These are discussed in more detail, along with a more comprehensive overview of upstands, in a separate blog post. Alternatively, contact our technical support team for detailing guidance specific to your project.

For more information, please contact IKO Polymeric’s technical team.