The regular BRE screed test can be inappropriate for floating screeds laid on insulation or quilt, as the impact can result I punching a section of screed through into the insulation. The modified method is described in Annex E of BS8204-1:2003&A1:2009.
The testing method is the same as that of bonded and unbonded screeds for screed Categories A and B (screeds subjected to heavy traffic and public areas), for screeds with a minimum depth of 75mm.
For screed category C (screeds subjected to light floor traffic), with a minimum thickness of 65mm, a 2kg annular weight is used in place of the standard 4kg weight, and the proposed indentation is limited to 2.5 mm instead of 5mm.
Interpretation of Results
If a fracture occurs during the test, it is to be recorded as the test result. According to the British Standards code of practice, a fracture leads to a truncated cone of material, which can be knocked out from the underside of the screed.
- A fracture of the screed can be determined by the change in note produced when the weight hits the anvil. When a normal blow would produce a ringing sound, a fracture is usually indicated by a dull thud, accompanied by a sudden increase in the depth of the indentation.
- If a truncated cone fracture is recorded during the first three drops the screed is to be considered unsatisfactory. However, a screed can be considered satisfactory if the fracture occurs only on the fourth drop and the indentation is within the appropriate limit.
- Any portion of the screed where the depth of indentation is greater than the relevant limit should not necessarily be rejected. Such screeds should be assessed by other means to ascertain whether they are fit for purpose. This can require the removal of samples for the determination of cement content, strength, thickness, etc.