We had been aware of an earlier bodge that was failing – close to the pre-school main entrance, there is a recessed under floor vent, e.g. a hole in the ground. The hole had been covered by a sheet of ply wood, that itself had been covered by a rubber mat. The ply had rotted and the rubber mat was not load bearing… so we covered it with fresh ply & worked out what to do.

At the time, we assumed this was under floor venting to the pre-school room, which often smelt damp & musty. So we ordered a custom fit metal grating from Midland Gratings – www.midgrid.co.uk (who were fantastic and reasonably priced), cleared out decades of dirt, leaves & lego, and built a support for the grating. This solution should be over-engineered: we don’t expect have to re-visit for a very long time, other than to remove leaves etc. The ply / rubber matting was impeding ventilation, the grating resolves that issue.

The area as at February 2024

The offending hole – enough to cause injury if the cover collapsed, hence attention was required (PS wall on the left):

The hole cleared and prepared for a new support (the vent through the external PS wall on the right):

The finished grating, with gravel covering the hole but free airflow into the vent / air brick:

And again (the sandstone surround is not perfectly flat, neither is the join to the tarmac & the rest of the carpark; the sandstone was retained due to the character that it adds):

Shortly after this work was completed, we replaced the floor of the room inside, and were able to see that this vent used to supply the fireplace inside, possibly in both of the preschool rooms. We assume that this vent still feeds the chimney (the fireplaces are both blocked up). The ‘black’ looking pipe mid picture goes from the fireplace on the right, to the below ground ‘air brick’ outside the room covered in the images above.