Waterproofing facades in practice

Will anything change with regard to the watertightness of façade structures after the introduction of the Built Environment Decree?

Even with the introduction of the Building Works Decree (Bbl), a building must be watertight. This public law requirement applies to the external dividing structures of a building of which facades are a part. But how did this regulation work, how can you test the requirements and what are the points of attention? Below is a brief description.

Laws and regulations

The test method for determining water tightness is described in NEN 2778. In addition to this Dutch legislation, it is stipulated at the European level that curtain walls, windows and doors must be CE marked. Part of this CE marking is the performance of a water tightness test in an accredited laboratory. Windows and doors are tested in accordance with NEN-EN 1027 and curtain walls in accordance with NEN-EN 12155. Both test methods are in line with NEN 2778. Then, on the basis of the test results, a door or window system is classified in accordance with NEN-EN 12208 and a curtain wall system in accordance with NEN-EN 12154.

At the project level, the facade builder must match the performance of aluminum facade elements to the specified requirements for water tightness. This concerns the minimum requirement from the Bbl or a possibly higher private law requirement laid down in the contract documents. The minimum test pressure to be maintained is determined in accordance with NEN 2778 and depends on the height of the building, the surrounding buildings and the wind area.

Why practice measurement?

The results of a laboratory test are sometimes not sufficient for a client or contractor to demonstrate the watertightness of a facade. This is because laboratory tests only demonstrate the watertightness of individual elements under ideal conditions and structural connections are not tested. In order to assess whether a facade construction actually meets the specified water tightness requirement, it is possible to carry out a practical measurement on a representative facade section of the project. The practical measurement is carried out in line with the standards mentioned above.

Our experience from practical measurements is that standard facade elements usually meet the requirements for water tightness, but there are exceptions. After all, execution remains human work. Certainly when high requirements are set for the water tightness of façade structures, a number of types of façade elements are critical. These include specials such as fire-resistant window frames, sliding doors, tambour doors and doors with limited curb (because of accessibility requirement Bbl). Besides omissions in the facade elements themselves, there may be imperfections in the sealing around the elements. By performing a practical test, the watertightness requirements are tested. In this test, an airtight test box is built on the inside of the facade element (see photo) and a sprinkler system is installed on the outside (see photo) in accordance with the mentioned standards.

Points of interest

In order to reduce risks of watertightness defects, it is advisable to test the detailing for air permeability and watertightness in advance. It also makes sense to carry out a laboratory test of a representative facade section in advance of production so that points of concern in facade elements can be identified at an early stage. However, these results are not representative of the practical situation. For this reason, it is valuable to make a test arrangement of the seals to be applied on site and have them evaluated. This will provide insight into the actual implementation and difficulties in the design. Finally, a practical measurement for waterproofing can be made. It is advisable to include the façade finish in this testing so that the final situation is tested. It is wise to carry out the testing as early as possible in the construction process. Possible points of attention and possible defects are then noticed in time and adjustments are often still easy to realize.

In summary, the procedure for achieving a watertight façade under the Building Works Decree for the living environment is no different than before and remains an important consideration at all stages of the construction process.

This article was produced in collaboration with Kettlitz Facade and Roof Consulting.