Have you been told you need to increase the ventilation under your suspended timber floor?
Do you have dry rot or wet rot issues?
Have you had a recent survey that has noted a springy suspended timber floor?
Have you got a strange smell / odour coming from your suspended timber floor
It isn’t unusual for the most common specification offered being additional sub floor ventilation. Please remember the ground beneath your suspended timber floor is going to get damp at some point. How much depends on how well your drains are functioning, no leaks, and also how wet the recent weather is.
I have surveyed many a suspended timber floor where extensive repairs have been carried out to try and fix timber decay issues like wet rot and dry rot that have failed.
It is always prudent to keep things simple and eliminate all potential defects before coming to a conclusion. A CCTV drain survey then becomes a must, as drainage issues from my experience are a common cause of excess moisture and subsequent timber decay issues within a suspended timber floor.
See this video that highlights the basics.