I am new here - hi everyone, looks like you've got a great little community of people helping each other. I'm from New Zealand, so our weather and typical construction methods may be a little unfamiliar but I'm sure you'll understand.
Basically, for several years we've had an issue with moisture entering one corner of the house. I have only just realized that it may be due to this air vent (pictured) in the concrete block base sitting at ground level.
Every other vent is raised above ground level, and this one is often clogged with leaves and debris as though rainwater has been flowing in here.
The lower set of holes in this grate look as though someone has at some point attempted to fill them up with cement or mortar, however they either did a poor job, or it has broken away over time.
To stop water flowing in here, I am considering either making a raised "lip" of mortar on the concrete in a semi circle around the opening, or perhaps just having a go with a silicone gun and filling all the gaps where the concrete and the vent meet, and probably sealing over the lower row of holes in the vent.
If you have any other suggestions for something that will be simpler, more effective and/or more durable then I would be very grateful.
Thanks very much.