Flat Roof Waterproofing

We often hear clients complain about problems with flat roofs.

Be it concrete flat roofs with torch on waterproofing,  timber flat decks with torch on waterproofing or Zinc Aluminum steel roof sheets – If the waterproofing system is not designed correctly then neither the best products nor the best labor will solve a waterproofing problem. One of the most common problems with residential properties is when home owners decide to extend their building.The quickest and easiest method chosen by architects is usually a flat roof that is tied into the existing roof.

The Architect may specify the type of material to be used but the waterproofing detail is usually left up to the builder to decide and often this is what happens…  No matter how fantastic the waterproofing product is, or how many years experience the waterproofing contractor has, no one is going to fix these types of problems  – this means re-roofing or replacing the flat roof covering with a new type roof covering more suited to the design of the roof.

roof waterproof

Roofing and Waterproofing are allied trades and work hand in hand with each other. The material and waterproofing system should be specified along with the design of the flat roof.

A flat roof that is being joined to an existing roof covering should avoid making use of internal box gutters. Box gutters are usually associated with steel flat roofs. There are ways to avoid box gutters. One such way is to design the flat roof so that it does not make use of them at all. A timber flat roof that is covered in torch on waterproofing can make this possible.  (see photo below)

Here timber ply-board is used to create the flat roof area. The boards are tied into the existing roof and extend under the roof tiles. The entire area is then waterproofed with a torch on membrane making it 100% leak free. It is a simple and elegant solution to a common problem.

 Waterproof Roofing

Note: The home in this picture originally had steel roof sheets extending from below the roof tiles. The steel roof sheets drained into an internal box gutter on the inside of the parapet wall. The result was constant leakage, ceilings that had fallen in and much frustration.

Since we installed the timber deck solution – not one drop of water has come through this area.


Sean Orme specializes in roof replacements and waterproofing in Cape Town