How do you avoid problems with roof detail on flat roofs?


More and more, bitumen flat roofs are punctuated by roof detail such as domes, upstands, roof edge profiles, etc. Too little attention is given to these critical spots and this results in problems later on. It is only when leaks happen that action is taken, while such damage can actually be prevented. We recommend taking the roof detail into account as early as the design phase. In this article you will learn how to best handle implementation details on flat roofs.

Problems with roof detail on flat roofs

Roof detail entails all the connections and finishes on flat roofs. Contractors and roofing sealers are often confronted with the complexity of this roof detail. They are difficult to seal with bituminous or synthetic membranes, and often need to be applied without using a flame. Architects should actually take such detail into account as early as the preliminary design stage. For example, they should ideally take into account at least 200mm of free space around the roof details. For any tricky details, roofing sealers can use a liquid waterproofing product such as Alsan Flashing Quadro. Alsan Flashing Jardin, in combination with green roofs, also has a root resistant effect.

Compatibility of materials

An important point of attention is when bitumen roofing membranes are connected to other elements. Since various materials are used, you need to pay particular attention to the compatibility of all the materials, especially for renovations. Combining different bitumen materials works perfectly. But bitumen in combination with synthetic membranes  sometimes requires different bonding techniques. For complex bonding, you should ideally use ALSAN liquid coating resins.


Different types of roof detail require different approaches

For sealing upstands and cills, it is best to envisage an upstand of at least 150mm  higher than the level of the finished roof surface. For roof edge profiles and wall caps, you need to ensure that the supporting structure contains sufficient movement joints. The architect should already have anticipated these aspects in the design.

The task of the architect

The architect should ideally consider the roof detail during the design phase so that adequate waterproofing application is possible. It is important that the aesthetic aspect doesn’t always take priority. Choose a proper solution instead and avoid problems and leaks later on.

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