Site testing may be used to check workmanship, occasionally it is used to check design performance.
As a check on design performance it is no substitute for controlled testing of a specimen in a laboratory.
Lessons learnt from site testing will not be fed in to the design but will only be used to assess options
for rectification work.
Site testing to assess wokmanship should be timely. It should be undertaken early in a project if the
desire is to improve workmanship, and at the end of construction if it is to prove compliance.
Air leakage testing
Whole building air leakage tests are required by Part L of the Building Regulations (England and Wales).
Air leakage arises principally from poorly designed interfaces between cladding packages. A whole
building air leakage test checks that interfaces and other sources of air leakage are correctly sealed. Guidance
on whole building air leakage testing is given in CWCT Technical
Water penetration resistance may be tested to check workmanship or design. Workmanship is checked using
the hose test whilst design is tested using an improvised cabinet test or in the case of patent glazing
and rainscreens a spray bar test. All of these tests are described in the CWCT
Technical Note TN41.
Thermal imaging can be a useful way to identify thermal bridges, the location of air leakage and other
factors that affect surface temperature of the building envelope. Thermal images have to be interpreted
with care to separate the different factors that may lead to variations in surface temperature. The
CWCT has published Technical Note TN45
which describes thermography and its use as a diagnostic tool
for building envelopes.