I have understood from experience that locating a leak in a flat roof can be somewhat difficult and expensive.  In our home it took 3 different roofers, making multiple visits, to identify the point in our flat roof that a leak was coming from.  The reason why identifying leaks in flat roofs is difficult is that very often the point where the leak shows in the ceiling below can be quite different from the point at which the leak is occurring in the flat roof itself. 

The most obvious places to look for leaks on flat roofs are flashing or joints or seals of any kind.  Now, flashings are used at the point at which the roof joins adjacent non-roofing material such as brickwork.  As an example above our kitchen extension we have a parapet wall at one edge of the roof and flashing closes the gap between the roof and the wall. 

As reported at flat roof company, a capable roofer will first examine such flashings to isolate gaps through which water could maybe pass. Flashings are typically made of a metal material like lead. 

It is also usually a problem to test for leaks on a flat roof in the way you would on other types of roofs. The reason is because it could take hours for water to trickle down to the ceiling below from the moment you poured it on a suspect area on the roof. This means that in reality it’s very hard to test and track multiple suspect places.  This is covered in more detail at the epdm flat roof web page.

The key to effective flat roof leak repair is to know in upfront the areas most likely to be vulnerable. The best test alas is to carry out the work to close suspect gaps and then wait to see if the leak persists. Hence flat roof repair depends greatly on the intelligence, honesty and experience of the roofer you hire.