I have had a constant issue with damp under my suspended floor. No rot as yet but the edge of one of my carpets smells musty and mouldy and this is coming up from the sub floor void. I think that the sub floor ventilation is insufficient. As you can see the airbricks (one of four at the rear of the house) have pretty small holes, and when I removed one of them there was some rubble behind it, not entirely blocking the hole but enough to impede air flow. So I’ve knocked up a prototype grill which I intend to sit on a fillet of concrete and seal around the edges. Is this feasible, or will there be any problems? Also, the front of the house has only two airbricks, one either side of the bay window about 3 metres apart. I feel that another one under the bay would be helpful. Is it doable to knock a hole in the (solid) wall there to open into the sub floor and fit a grille? Any advice would be greatly appreciated.