Flat Roof Upstand Height

The design of drainage falls should ensure that the continuity of the waterproof covering is maintained for a vertical height of 150mm above the finished roof level at all abutments door openings and parapets upstands are there to deal with the fact that rainwater can build up on a roof during heavy storm events.

Flat roof upstand height.

The job of an upstand sometimes referred to as a kerb is to lift the glass element of your rooflight off of the roof s surface and is required by building regulations for safety and weathering reasons. 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. Which would include abutments rooflights and service vents etc must have a minimum height of 150mm. The design of drainage falls should ensure that the continuity of the waterproof covering is maintained for a vertical height of 150mm above the finished.

The requirement for flat roof upstands is set out in the british standard. Bs 6229 2003 flat roofs with continuously supported coverings code of practice and bs 8217 2005 reinforced bitumen membranes for roofing code of practice both state that if unwanted water ingress into the building is to be avoided all weatherproofing upstands occurring around the roof area. The overflow must be a minimum of 25mm below the top of the 150mm upstand height. The design of drainage falls should ensure that the continuity of the waterproof covering is maintained for a vertical height of 150mm above the finished roof level at all abutments door openings and parapets.

Note also the requirement for an overflow if the waterproofing covers an enclosed area with an upstand all around such as on a balcony or roof terrace with a parapet. The requirement for flat roof upstands is set out in the british standard. This dimension should be measured from the finished surface of the roof which would. The upstand is usually installed on a pitch to allow water to drain off the rooflight further increasing the upstand height.

This is particularly important when adding rooflights to flat roofs as many waterproof membrane companies will insist that an upstand of 150 mm minimum is constructed in order to maintain the roofing material guarantee. The minimum upstand height for a single ply membrane flat roof is 150mm. It is critical to achieve the minimum upstand height at the same time as providing adequate falls for drainage.