Tech Update: Site Tests for Water-Tightness of Facades

Site Tests

Water-tightness can be tested on site using three different approaches, these being the hose, the spray bar and the cabinet.

To ensure that the on-site testing is carried out to a repeatable, consistent and industry recognisable standard a UKAS accredited testing house should be used.

When carrying out these tests the internal finishes it is a requirement that the internal finishes are removed from the perimeters of the openings so that any water ingress can be observed and recorded. 

Hose Testing (CWCT Section 9, AAMA 501.2-09)

Hose testing utilises a compressor to force a consistent flow of water through a nozzle, to produce a standard jet of water. The nozzle defines, as does the pressure of water entering it, the flow rate of the water passing through the nozzle. The jet of water is directed at an angle that is perpendicular to the plane of the cladding system and at the same, fixed distance from it.

The hose test should only be used to assess permanently sealed joints. The jet should not dislodge gaskets or cured wet-applied sealants unless they have been poorly installed.

Standard hose testing is unsuitable for open joints (e.g. rainscreen joints) or joints which are intended to open (i.e. window perimeter joints) even if baffled.

The weathering gaskets of doors and opening lights of windows are made of a softer rubber compound, largely to ensure that the door/window can be operated frequently without difficulty. These seals are not capable of resisting the jet from a hose, they will not be damaged by the water pressure but will be pushed aside allowing the system defences beyond to become overwhelmed and fail. Therefore, the hose test should not be used to test these seals.

Whilst a hose test could be used on an open or opening joint, this would require the water pressure to be reduced so that the distance from the nozzle to the wall could be maintained. This would no longer be a standard test. Therefore, the spray bar test is more applicable to this kind of joint.

When hose testing internal corner joints the hose should be positioned 0.3m from both walls (rather than 0.3m from the joint). This takes into account of the water which will be re-directed off the walls and towards the joint.

Hose testing can also be used on sloped claddings, as long as the jet is aimed perpendicular to the joint.

If a volume of water is required to simply observe its flow and drainage from your cladding/roofing, then the spray bar test is probably better suited to the task.

Wetting of the test area should begin at the lowest horizontal joint, rising upwards progressively via intersecting vertical joints to the next horizontal joint.

If there is leakage of water that is hard to locate, it is recommended that all joints to be tested are sealed with masking tape and which is progressively removed to expose the joints on by one. Once the source of the leak has been discovered and it has been fixed, the area should be re-tested.

Spray Bar Testing (CWCT section 10, BS EN 13051)

The purpose of a spray bar is to provide a spray of water over the face of a cladding system.

Spray bar testing is suitable for open-jointed systems (e.g. rain screen cladding and unsealed patent glazing) and the perimeters of opening vents, such as windows, because water is not directed at the joints.

This test is particularly useful for viewing water flow around elements that penetrate systems.

A spray bar consists of a long rigid pipe fitted with holes/nozzles at regular intervals along its length.  The spray bar will spray water at a set working pressure range, ensuring a constant film of water is sprayed onto the face of the cladding system. Spray bar nozzles can be directed at specific joints but it is better that they are directed at points above the joint

The spray bar test is a test for resistance against water penetration from water runoff. For that reason, the placement of the spray bar in relation to open and protected joints (e.g. under projections) should be properly considered.  

Cabinet Testing (BS 5368: Part 2)

Site cabinet testing involves a cabinet that can be sealed to the cladding system, it incorporates a means of pressurising or de-pressurising the cabinet and works in combination with a spray bar system.

Cabinet testing creates a pressure difference on the cladding system, whilst spraying water onto the external face. This technique can be suitable for the testing of doors and windows, including interfaces, once they’ve been installed. However, there are problems with applying this test in practice:

  • A primary issue is where to fit the cabinet in the first place. If the cabinet is mounted on the external face then it will be necessary to positively pressurise the cabinet, which will try to push the cabinet off the cladding system requiring that some form of restraint is provided. External fitting can also be difficult if the test area is above ground and access equipment needs to be provided. If mounted internally the cabinet will generate a negative pressure, which will help to hold it in place but will limit access to the internal surface of the cladding system making it harder to inspect for signs of leakage.
  • Another issue is how to prevent lateral air movement through your wall. Pressurising or depressurising a section of wall may bring air in from the sides (reveals), rather than straight through the part of the wall that you are actually investigating.
  • Lastly, the finished surface of your wall may not permit the easy attachment or the actual sealing of the test cabinet. As a consequence, many cabinets are built in-situ and are specific to one part of the cladding system.

These problems mean that the cabinet test is rarely used on site

The cabinet construction can use a multitude of materials such as plywood or polythene all have their advantages and disadvantages, and the other test parameters such as water flow rates, nozzle quantity/positioning/spacing, cabinet pressures and calculation of pressure losses all need to be very carefully considered. It is very important that a UKAS accredited test house is engaged to ensure that appropriate test parameters are selected so that the results remain meaningful.

Site Remediations

If the on-site tests identify water ingress and that remediation measures are required to façade installation these need to be carried out. The water test should then be repeated to ensure that the remediation has been successful.

If the test identified a fabrication, installation or workmanship error then all other similar installations need to be checked (possibly with additional water testing). The remediation measures need to be repeated where necessary and incorporated in the Quality Assurance checklist and inspection process for any future installations.

If the test identified a failure in the design and the remediation measure required a modification to the design, then the modification needs to be applied to all similar installations and the as built drawings need to be amended to capture the changes.


To view an overview of site testing for water tightness click here

For more information on facades and cladding in general visit the CWCT website. 


Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. Any written guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.


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