Angle Fillet in Waterproofing

One of the most common issues in waterproofing that keep recurring is the angle fillet. The angle fillet often occurs in toilet and bathroom waterproofing, besides balcony waterproofing.
Most of the contractor facing this issue may not be able to rectify the cause of the waterproofing. However, these contractors would just apply temporary surface waterproofing. As time passes, water seepage occurs through the angle fillet, thus causing the problem to recur.
If you encounter an angle fillet issue, it is best to engage your waterproofing specialist to fix the issue permanently. Most people may only do surface treatment. They do not fix the underlying deficiency in the cross section of the angle fillet. Hence, it usually recur, resulting in additional time and money spent to rectify this issue.


An Angle Fillet is known as a triangular cross-section that is designed to fit into the corner where two section meet. A Firring however is a cut along the fill length diagonally. They both serve for two purposes:

  1. The first is to prevent the sharp corner from somehow damaging the felt or membrane.
  2. The second purpose is to allow water to run-off easily.

Common problems when installing the angle fillet to a building or rainwater outlet treatment are:

  • the fillet deviates from the measurement
  • issues with fillets between the surface
  • fillet merging problems
  • the wrong measurement of the fillet

In order to resolve such problems above is that you should measure the fillet joint accordingly before getting it into action. In the next case, it might be best to use a Constant Width fillet, but it is only available for face fillets. For the fillet merging problem, changed the chamfer on that edge to 0.025.