Failed screed. Not something that anyone wants to hear.
This project in the midlands had some deteriorating screed, and after much debate with the builder, both sides offered a different opinion. The solution was to conduct a drop hammer test (also known as the BRE Screed Tester).
The drop hammer test is defined in BS8204-1:2003 and was designed to test the screed’s soundness whilst still in situ.
4 repeated blows with the drop hammer, and then the indentation is measured against the standard. The test will determine if you have failed screed.
In this case, all the readings were above the 2.5mm required to meet category C (domestic use). The worst reading coming it at 7.3mm.
The client could then speak with the build armed with fact-based results.
Further to the test, the screed was removed and replaced.