Cracks treatment in the surface coating of prefabricated building exterior walls

23 / 03 / 2022

Cracks treatment in the surface coating of prefabricated building exterior walls

Reasons for cracks in the surface coating of prefabricated building exterior walls

For cracks in the joint surface coating of prefabricated building, many people think that the displacement ability and adhesion of the construction sealants are not enough, but it is not.
Compared with traditional building silicone sealants, silane-modified polyether sealants for prefabricated buildings have better paintability and can form good adhesion with exterior wall coatings to ensure that the coatings do not fall off. But why do cracks still occur? The fundamental reason is that the displacement resistance (less than 5%) of ordinary coatings used in building exterior walls is far less than that of building silicone sealants. Cracks will appear on the surface.
Over time, the cracks will slowly expand and extend, leading to the misconception that there is a problem with the sealant's ability to displace and bond. It can be seen that it is very important to choose a good silicon sealant brand.

How to solve the crack when it caused?

At the same time as the rapid development of prefabricated buildings, due to technical reasons, in the actual construction process, many details that affect the quality of the project deserve the attention of the industry.

At present, in order to achieve a good waterproof and sealing effect in the prefabricated buildings of concrete and steel structures, silane-modified polyether sealant is generally used at the joints of the external wall panels to fill the joints.

There are three processing methods as follows:

1. “obvious gaps” treatment

Directly seal the gas by MS silicone sealant which is suitable for the case where the seam error is small.

2. ‘’Partial coverage“treatment

Using the silicone seam as part of the divider, coat the edges of the sealant seam with paint to match the width of the divider. Silane-modified polyether sealant can form a good combination with the paint due to its good paintability, and the exterior wall paint can be applied directly after applying the matching interface agent on the surface of the silicone joint seam.

3. “Full coverage’’ treatment

①You can choose to cover the elastic coating directly on the surface of the silicon joint, and the method is the same as the partial covering method.
②Use materials with excellent crack resistance at the joints: crack-resistant mortar, flexible putty and elastic exterior wall paint, and carry out net hanging treatment.

There are still large vertical and horizontal errors in the installation accuracy of prefabricated building panels and the gaps in the exterior walls of prefabricated buildings. In actual construction, the full coverage of glue joints is often used.
However, there is an unavoidable problem in the full coverage treatment, that is, the joint surface coating will crack after a certain period of time, which will affect the appearance.

Based on field visits of multiple engineering projects, multiple experimental measurements in the laboratory, and related technical service experience, Jointas gives the following suggestions for the surface treatment of the external wall joints of current prefabricated buildings:
1. When the gap conditions allow, ’’the obvious gaps’’ treatment method is adopted, and there is no need to worry about the problem of surface coating cracks.
2. In the case where’’ the obvious gaps’’ treatment cannot be used, try to use ‘’the half-cover’’ treatment method, and design the plate joints as part of the separation seam, which can also avoid the occurrence of paint cracks to a certain extent.
3. When using the ‘’full coverage’’ treatment method, be sure to choose high-quality anti-cracking mortar and elastic paint, and strictly control the construction quality of the paint.

Antas, as one of the earliest sealant brands to enter the field of prefabricated construction adhesives in China, has been providing assistance for the development of prefabricated buildings in China!
Over the years, Antas construction adhesive has continued to export high-quality products, a continuous and sound technical service network, and professional service capabilities to the industry. In the future, Antas will always adhere to the spirit of craftsmanship, continuously optimize products, improve processes, and produce and promote higher quality sealant products!