Hi Peoples. Its been a while. Was hoping to get some help. I am nearing the end of a personal job to build an gym/pergola/man cave/glorified shed. 6x3 structure, consisting of 3M 100mmx100mm posts that sit in metal shoes, that sitting in a concrete foundation. Im not a tradesmen so just learnt as i went along really, so i know things havent been done as they "should" be. The issue I have is, we laid concrete over an existing flower bed, and didnt really go that deep. was about an inch or 2 of concrete - and now it does look like I have some water ingress seeping through in parts. Assuming where water is collecting, or could be coming from undeneath. Area where we live also has a high water table. Not really feasible at all to lay more foundation and dig as the structure is complete now. I need to lay down gym mats on the floor, so this was a worry. My plan was one of the 3 below to alleviate the issue: 1. to put down some leftover roofing felt down, then some polythene sheets, followed by a some cheaper rubber mats, and my final more expensive mats on top. IT just worried me it didnt really resolve the issue, and months, years down the line would i find a bigger problem underneath at some point. 2. Timber frame to create an air gap between concrete base and mats which are laid on top. More cost, which i am loathed to do or can afford. 3. Ontop of the current concrete base put some sort of levelling compound, which i am hoping you can get with some waterproof properties? Purely a guess and not sure if this is possible. Appreciate you dont have the full history, but given the scenario above would be keen to hear your thoughts?