The facade is the face of a building but its significance in contemporary architecture goes much beyond mere appearance or visual appeal. Modern day facades find expression in the form of large dimensions, unconventional shapes and high material diversity. However, with these unique shapes and connections, joint design is demanding and prone to mistakes. For integral joint specification, following a few guidelines will result in a long-lasting and tight building envelope.
Four key considerations to achieve long-lasting and tight building envelope joints
The joint width is calculated from the dimensions and thermal expansion coefficients of the facade elements and the maximum and minimum temperature your facade will be exposed to after installation.
The maximum and minimum joint width defines which movement capability the joint sealant will need to be able to withstand the daily and seasonal cyclic thermal loads. To simplify your choice, sealants are classified according to their movement class by several standards.
Materials to be joined
Depending on the design of your facade, it may consist of facade elements of different materials such as concrete, glass, metal, brick or stone, just to mention the most common. These elements not only have to be sealed to each other but also to other waterproofing products such as membranes or structural glazing elements consisting of glass, metal frame and silicone adhesives.
The sealant must show sufficient adhesion to the materials involved in the joint and at the same time, must be compatible with all materials to avoid discoloration, loss of adhesion over time or any change in properties.
Environmental conditions have an impact on the service life and performance of the sealant. Conditions such as the level of UV radiation or the chemical environment the sealant is exposed to must be considered when choosing the product.
Additionally, when sealing between the inside and outside of the building, the vapour permeability of the sealant must be considered to avoid accumulation of water in the walls. The general rule is to use a sealant with lower vapour permeability on the warm side of the wall, as warm air is generally more humid than cold air.
Ugly joints are like scars on the facade. Therefore, when specifying the joint sealant, the visual appearance of the joint must be considered. Besides the colour matching to the facade elements and the toolability of the sealant, there is also staining on natural stone or streaking on glass to be considered.
Staining and streaking can damage the appearance of the whole facade and are irreversible. In this case, stone and glass would have to be replaced. Hence, save money by using non-staining and non-streaking products where required.
What Sika provides to make sealants last
Wrongly specifying joint sealants will eventually lead to leakage within the building envelope with significant impact on operation and maintenance costs of your building. The key is to avoid making mistakes where your building is most vulnerable.
- Sika offers know-how and a broad range of solutions to meet all waterproofing requirements of buildings, from foundation to roof. The best waterproofing results are achieved when choosing all solutions from one provider.
- Building envelope sealants and structural glazing adhesives are some of Sika’s core businesses with a long tradition, top global references and sound expertise.
- Sika sealants have best-in-class handling properties. As a longstanding partner of applicators worldwide, we know what they need to do for a perfect job and how to surprise their customers.