Facades are amazing. The level of skill that goes into designing and installing facades, never fails to impress me and not just from an aesthetic point of view. The performance requirements of a facade system are immense. From the structural requirements to dealing with weather, facades are one of the most complex elements on any high-rise building.
Despite the complex nature of these systems, I frequently see evidence of ‘repairs’ being undertaken by people that do not understand how the system works and rather than repairing the facade, they create problems. For the individuals being instructed to ‘fix a leak’ and not knowing how the facade works, you do the only thing you can think to do and seal every hole and joint you can find.
The image above is an example of how NOT to repair a facade. The black flashing tape on the mitre joint of the window frame was aged in appearance, had obviously been there for a while and I’m assuming was the first attempt at a repair to address a leak near this window. This mitre joint would not have been the cause of a leak. All mitre joints open and close to some degree as a result of normal expansion and contraction and allowances for this are made in the design. The facade has mechanisms to manage any water that enters the window frames – weep holes and open drainage joints below the frame allow water to drain.
The left-hand image above shows a normal open drainage joint beneath the window frame. If you look closely to the left of the joint, you’ll see a small drop of water draining from the joint. The right-hand image shows a weep hole performing it’s role and allowing moisture that has entered the frame to drain freely.
The application of the black flashing tape on the first image obviously did not address the leak so, on what appears to have been another round of repairs, the weep holes were covered with a different type of flashing tape and the drainage joints below the frame were sealed with silicone. The result of all this – water is now trapped inside the facade at this location.
These photographs were taken during a maintenance plan inspection and it is not possible to say, with any degree of accuracy, what caused the leak that prompted these repairs. It is possible that the concealed internal seal is either missing or defective and rain has been driven inside with the help of strong winds. Without seeing stain patterns inside or a thorough inspection of the external and maybe some opening up, this is just an educated guess. What we can be certain of however, is that blocking drainage on a facade, it not good for the building.
Water will always find a way and if you block the intended drainage path, you can be sure it is finding its way somewhere you don’t want it to be. My advice to anybody involved in the maintenance of high-rise facades is to make sure you understand your facade before starting repairs and make sure the person doing the work is a specialist. The willing abseiling window cleaner is unlikely to have any idea that trapping water in the facade will cause deterioration of components you can’t even see.
by Victoria Richardson