This method will apply to all properties built with traditional foundations.

The property may however have been built on a raft foundation due to poor ground conditions, mining subsidence etc.. 

Where a raft foundation is found it is usually not necessary to take and test a sample of the hardcore infill as the amount of hardcore infill under the raft is likely to be very small, the raft will be usually minimum 200mm thick, will be a stronger concrete mix than in a normal traditional floor and will be reinforced with steel mesh reinforcement. 

Taking all these factors into consideration we interpret current BRE guidance as indicating the Building Research Establishment say that even if sulphate containing industrial fill is present under the raft foundation, the rate of attack on the concrete is unlikely to exceed 1mm per year making the risk of damage minimal.