mortar missing from above lintel over one of my basement's glass block windows - between the lintel and the brick directly above the gap.
From some research on the internet, I think this space could/will allow water to get in, maybe into the wall and eventually into the basement.
Also, from some research, I think I should only fill the space directly above this lintel with a permeable material, so that any water seeping down through the bricks will be able to get out, instead of being trapped between the non-permeable filler (caulk or whatever) and the vertical (back) part of the lintel behind the brick.
If true, what is the correct material with which to fill this gap? Maybe a 3:1 mortar mix? Certainly not a caulk of any kind? What about the mortar repair stuff that comes in a caulking tube - is it permeable?
Thanks in advance.
PS - yeah, the lintel is rusting; so, I'll remove the rust and then paint it.