CWCT testing
CWCT testing means testing a curtain wall or other building envelope to the methods published by the Centre for Window and Cladding Technology. It happens at two stages: in a laboratory, on a full-size sample of the system or a project mock-up, and on site, once the wall is installed.
The laboratory tests prove the design keeps out air, water and wind; the site tests check the workmanship of the joints that were actually built.
Guide price: priced per test programme; site hose testing per day
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When testing is asked for
- A new system or bespoke design that has no laboratory evidence yet.
- Larger unitised projects, where a full-size mock-up is tested before production.
- Structural warranty conditions, which often require on-site water testing.
- A client or consultant specification calling for testing to the CWCT standard.
- Leak investigations on an existing facade.
- Disputes about workmanship, where independent evidence is needed.
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What affects testing costs
| Item | Typical figure, ex VAT |
|---|---|
| Laboratory sequence test Rig hire, sample build and the test sequence; mostly borne by system companies or on large projects | Per programme |
| Project mock-up test Usually included in larger unitised or bespoke packages | In the package |
| On-site hose test A UKAS-accredited team on site, priced per day plus access | Per day |
Where these figures come from
Test houses quote per programme or per day, and do not publish rate cards. As a rule of thumb, ask for site testing to be priced as a separate line in the curtain walling package, with the number of test visits stated, so that retests after failures are clear.
Need a hose test or a leak investigation on a facade? Tell us about the building and we will look for a specialist.
Get matched3
The tests, in order
The CWCT Standard for systemised building envelopes, published in 2006, combined the earlier curtain walling, rainscreen and slope glazing standards and sits alongside the product standard BS EN 13830.
Laboratory sequence
A sample at least one storey high and two bays wide is built on a test rig. It is then put through a set sequence, so later tests show whether earlier loads have damaged the seals.
| Test | What it shows |
|---|---|
| Air permeability | How much air leaks through the wall at set pressures |
| Water penetration, static | Whether water gets in when sprayed under steady pressure |
| Wind resistance, serviceability | Whether frames deflect within limits under design wind load |
| Repeat air and water | Whether the wind load has harmed the seals |
| Water penetration, dynamic | Whether wind-driven rain gets in, using an aero engine or fan |
| Wind resistance, safety | Whether the wall stays safe under a higher, factored load |
| Impact (where specified) | Resistance to soft and hard body impacts |
On-site hose testing
Site testing checks the joints that were built. In a hose test, water is sprayed from a nozzle held 300 mm from a joint and moved along it, while someone inside looks for leaks; it suits joints that are meant to be permanently closed. A spray bar test runs a film of water down the face from a bar above the joint, which suits open-jointed systems such as rainscreens. BFRC describes both methods.
Structural warranty providers commonly ask for at least 5% of the length of critical joints to be tested, spread across every elevation and including the top quarter of the building, by a UKAS-accredited organisation, before internal finishes hide the inside face.
Reading a test report
Check the report names the system and sample exactly, gives the pressures and classes achieved, and lists any failures and what was changed before a retest. A report for one system does not cover a different profile, glass make-up or a larger pane size.
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How a site test visit runs
Agree locations
Test areas are marked on elevations and agreed with the client and warranty provider.
Prepare
Access is arranged outside and the inside face kept clear of finishes so leaks can be seen.
Test
Each joint is tested in turn and any leak photographed and recorded.
Report and retest
A report is issued; failed areas are repaired and tested again.
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Questions people ask
What is CWCT testing?
Testing of curtain walls and other building envelopes to methods published by the Centre for Window and Cladding Technology, covering air permeability, water tightness, wind resistance and, where specified, impact.
What is a CWCT hose test?
An on-site test where water is sprayed from a nozzle about 300 mm from a joint and moved along it while someone inside checks for leaks. It is used to check the workmanship of installed joints.
Is CWCT testing a legal requirement?
No law requires it, but CWCT standards are the accepted best practice for curtain walling in the UK, and specifications, clients and structural warranty providers commonly make testing a condition.
How much of a facade needs to be hose tested?
A common warranty requirement is at least 5% of the length of critical joints, spread over each elevation and including the upper part of the building. Your specification or warranty provider sets the actual amount.
Who carries out CWCT testing?
Independent test houses with UKAS accreditation for the relevant methods. Laboratory sequence tests need a test rig; site tests are carried out by a visiting team.
Find a curtain wall testing specialist
Location first, then the package, then your contact details. Each step is short.
We are an introduction service, not a curtain walling contractor. We look for one that covers the project and name them to you first; nothing is passed on until you agree.
Thanks, we have your enquiry.
- We look for a curtain walling contractor that covers the project and handles this kind of package.
- When we find one, we email or call to tell you who they are. Your details reach that firm only if you say yes.
- They review the drawings or the building and price the work. No marketing from us.