Have an independent professional specify the correct solution in a schedule of works which will allow contractors to quote
"Ben provided a very clear and detailed report (Damp survey and Flood resilience report) with a very swift turn around. He was flexible about when he could conduct the survey and very understanding when, at the very last minute, the vendors had to rearrange his appointment. He ran through the report over the phone afterwards and had helpful and informed answers to my questions. I would happily recommend this service"