I have damp in the sub floor of my 1930's bungalow. The original tar coating has perished in places and this is allowing damp in and also giving off a mild tar like smell. This appears to have been a long standing issue as a couple of the floor joists are damaged with wet rot and need replaced. There is no pooling and the smell goes away when we have a dry spell.
My first course of action is to increase the ventilation under the floor to help dry it out. I know the bricks don't line up so putting a rectangular air brick in will be awkward. Is it acceptable to use a coring drill (like those used to make the holes for extractor fans) and suitable plastic tube and vent cover or do I have to use the rectangular covers?