Stroma Built Environment delivers comprehensive onsite CWCT Testing to determine if building envelopes are weathertight, airtight, and watertight. We are experienced working across various construction projects, with a third-party supplier for providing UKAS certification. 

What is CWCT Testing? 

CWCT stands for Centre for Window and Cladding Technology. CWCT Testing is a crucial part of assessing the integrity of building envelopes. By investigating the performance and quality of facades and rain-screen cladding systems against air, water, and solid object impacts, CWCT testing helps clients mitigate risks and unexpected costs. 

Our experienced assessors can deliver a range of CWCT testing services, including water penetration testing, air permeability testing, and impact resistance testing. While CWCT doesn’t guarantee the overall performance of a given building, it offers reassurance that the glazing and cladding will withstand a range of typical UK weather conditions. 

CWCT Testing Standards 

CWCT standards cover water tightness, air tightness, wind resistance, and impact resistance. The CWCT Standards for Systemised Building Envelopes is part of the National Building Specification and specifies individual project requirements for water tightness, air tightness, wind resistance, and impact resistance. 

The guidance includes a checklist outlining internal and external environmental considerations, air permeability, access and safety measures, thermal performance, and design life expectations. It ensures appropriate standards for the finishing and appearance of building envelopes per relevant UK Building Regulations and industry best practices. 

Water Tightness Testing: Hose Testing 

The hose test is used for sealed (closed) joint curtain walling and sloped glazing systems. It involves spraying water from a single nozzle at a distance of approximately 250mm. The hose will then be moved closer over controlled intervals for around 30 minutes. 

This testing method should be carried out following specific standards defined by CWCT. 

  • CWCT Standards for Systemised Building Envelopes: 2006
  • AAMA 501.2-09
  • NHBC Standards 2011 Chapter 6.9 S10
  • CWCT Section 9
  • CWCT TN 41
  • AAMA 501.94 & 501.2-09

Water Tightness Testing: Spray Bar Testing 

The spray bar test is used to identify leakages in open-jointed systems (rain-screen cladding, unsealed patent glazing, curtain walling systems, roofs, and skylights). It involves mounting a horizontal bar with nozzles spaced at intervals of 400mm above the test area for 30 minutes.  

The flow rate is calculated depending on the number of nozzles, per specific standards defined by CWCT. 

  • CWCT Standards 2011
  • NHBC Standards 2011 Chapter 6.9 S1
  • CWCT Section 10
  • CWCT TN 41
  • BS EN 13051:2001

Water Tightness Testing: Cabinet Testing 

In cases where an internal cabinet can be assembled, the cabinet test offers another method for assessing water tightness. While negative pressure is applied within the cabinet, a spray bar should be positioned externally. As the negative pressure increases, assessments can be made at different levels until maximum pressure is reached. 

Benefits of CWCT Testing 

CWCT testing is vital for providing peace of mind regarding the performance, quality, and compliance of facades and cladding systems. 

  • Accurately simulate leakages for various building envelopes
  • Identify potential weaknesses to address before installation
  • Determine causes of façade failure to inform improvement methods
  • Predict expected performance levels to optimise maintenance strategies & costs
  • Ensure products comply with relevant regulations & industry standards

Stroma Built Environment for CWCT Testing 

CWCT Testing is critical in ensuring the performance and safety of building envelopes by subjecting them to rigorous inspections under various climatic conditions. Adhering to CWCT testing standards not only establishes the quality of your facades and cladding systems but also provides a framework for specifying products that meet project-specific requirements. 

Stroma Built Environment and its team of experts are here ready to discuss a range of packages for any new project. Get in touch today! 

Frequently Asked Questions

What is water tightness testing?

Water tightness testing is a key aspect of CWCT Testing and involves 3 types of water tests: hose, spray bar, and cabinet. These tests aim to determine the effectiveness of a façade system in preventing water from penetrating the interior. Achieving water tightness is essential for ensuring buildings remain dry and protected from leaks. 

What is wind resistance testing?

Wind resistance is an important part of CWCT Testing. It simulates the wind blowing towards or away from the exterior of a building by applying positive and negative pressure. This is carried out to ensure the cladding system can withstand extreme wind conditions without failure. 

What is safety wind load testing?

Safety wind load testing is another method of CWCT testing which involves subjecting cladding systems to extreme wind loads. This test is usually conducted on flexible cladding systems where permanent deformation and stress limits have been exceeded. It is crucial for ensuring the strength and integrity of building envelopes during severe weather conditions.