Lessons Learned Log
A late supply chain substitution swapped the specified vapour control layer for a vapour permeable breather membrane from the same product family. The delivery paperwork still referenced the original product code, so it was missed at goods in.
Moisture became trapped in the wall build-up across a batch of occupied units. Residents reported damp and mould before the fault was traced. Once decant costs and remedial works were included, the total came to around £1m.
An independent moisture survey established how far the problem extended. Affected plots were strip-backed and reinstalled to the correct specification under the warranty provider's oversight, and every plot delivered under the same batch code was audited to rule out further exposure.
A product substitution should never be waved through as like for like on a supply chain email. Lock the membrane specification at design freeze, and add a first-fix inspection checkpoint that physically confirms the installed membrane against the drawing reference, not just the delivery note.
This lesson is tagged to Example LGS Panelised Wall System.