Thanks,
What do you think should be done with these pits in the sub floor, which I assume are going down to the water table as they are wet. Would filling them reduce the humidity.
On Monday, 18 November 2019 14:57:45 UTC, Tricky Dicky wrote:
The first thing you need to do is get the ventilation right. It is possible to have the air vents below ground level but you need to fit pipes large enough not to obstruct air flow and at the top the pipes need to be angled and have angled louvres on the ends to prevent water ingress. However this not your only problem as if the patio level is above the vents it will also be above any damp course level. You will need to excavate a trench along the patio/wall interface below the the air vents by about two bricks you can then put gravel in to act as a French drain, ideally with some means of draining away although for a short bout of rain it will simply drain into the soil.

As for the rot wet rot is the easier to deal with cut away any rotten timber and replace. Dry rot is the bigger problem if it has tendrils spreading across the timber then that is dry rot and you need to cut back all affected timber at least 600mm past the furthest extent of the rot. What remains must be treated including any brickwork in the vicinity to kill off any spores. To be honest it is a specialised job and I would recommend you get a company in to identify the rot and if need be treat it.

Richard