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The Importance of CWCT Water Tightness Tests For Your Construction Materials

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Safety remains a central theme in discussions regarding the construction industry as regulators tighten the noose on acceptable product standards. Your building facades may have to endure years of brutal weather while not significantly losing structural integrity. 

One of the most common reasons for facade failures is water leaks. Substandard materials can result in water seeping through the building envelope, threatening the structural integrity of your construction. 

To ensure that the products used in your construction are durable and of excellent quality, you can use CWCT certifications as a guideline to find robust material for your project. 

CWCT Testing 

The Center for Window and cladding technology is an independent body that provides standards and guidelines for wall cladding and window facade testing. The water tightness analysis is part of the recommended test series, performed alongside air permeability, wind resistance, and impact testing. 

What You Can Expect During CWCT Water Penetration Tests 

No two construction sites are identical. You may require customized claddings for your project. Understanding the test processes can help you pick out products that meet your design needs. 

CWCT recommends two main protocols for water permeability: the hose tests and the CWCT spray bar tests. Here is an in-depth look at each testing process and its impact on your building material. 

Hose Testing 

Hose tests are present in Section 9 of the CWCT standard booklet. The testing team forces water through a nozzle directed perpendicularly to the material, creating sustained pressure on the joints under review. 


The CWCT hose test suits your building’s permanent seal joints in curtain walls, window facades, and exterior cladding. It is also popular in sloped glazing systems. 

Hose testing is not recommended for open seal joints as the water pressure may damage the weathering gaskets on the windows or door frames.


Testing companies deploy a compressor that creates a water jet directed at the material at hand. For consistent results, the nozzle used, flow rate, and water pressure through the nozzle need to remain constant. 

The water spray from the nozzle ought to hit the object at a perpendicular angle. The testing crew also maintains a fixed distance from the nozzle to the test material. 

CWCT Spray Bar Test

The CWCT spray bar confirms the water tightness of the cladding or facade by using a water spray directed at the surface. The specifications and modules for the test are present in section 10 of the CWCT standards booklet. 


The test is suitable for open joint systems, for example, rainscreens. It is also helpful in testing facade components containing opening joints such as doors, cladding, and unsealed patent glazing. 

The test contractors examine the interaction of the facade system with the water runoff. 


The testers begin by setting up a test rig with the cladding or facade material put in place. The spray bar has holes drilled at pre-determined lengths. The holes generate a water spray directed at the surface of the test material. 

The test conditions dictate the use of a constant flow rate and pressure at the holes. The length between the spray bar and the cladding or facade should be consistent throughout the test. 

The water spray should hit right above the joint, allowing the water to flow over the seals. The technicians can then assess the material product for impermeability. 

Pass or Failure Criteria For CWCT Water Permeability Tests

Rainscreens and window facades used in your construction need to be impervious to water. The test conductors may need to ensure that no water penetrates to the inner backing. Additionally, no water should stand in areas that should be dry. Products that pass the test receive a CWCT certification. 

You may use the CWCT certification as proof of the quality of the exterior claddings used in your building. 

Hiring the Right CWCT Testing Companies

CWCT is an independent body with members from across the construction industry who define the specifications through the Standards Committee. You may need to find a certified test company and a member of the CWCT to help verify the quality of the products. 

Additionally, you may inquire about customized orders. Your construction projects may require customized facades and curtain walls depending on the final height of the building. You may need to find a testing company that can tailor the tests to meet your needs. 


Water permeability tests are critical checks that guarantee the quality of the construction materials you use. The CWCT provides specifications and modules for running the assessments necessary for your building envelope. Remember to select the right testing company for your product diligently.

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