Last night I heard scratching in the wall and upon investigation found that a squirrel had managed to knock loose a piece of wood (I assume as there was no covering to be found) in the eaves where one level of roof (over main house) drops down to a second level of roof (over garage). As a temporary measure, as I had no other readily available supplies, I blocked the hole with some scrap wood and nailed in place until I could create a more permanent fix. My question is what would be the best approach.
The external hole itself is approximately 6"x 6" (I say approximately as it is really an isosceles triangle) and seems to be a no brainer (prep a board that I cut to size, nail in place). My question is really for backing behind it. In my limited examination looking into the gap I could see some posts that I believe was some of the beams from the attic. The total gap size is approximately the size of a toaster (could not think of how else to describe it).
Should I try to use some foam spray, and would that work (space seems a bit large for this to work properly) or otherwise fill in the space in some other way? My concern is less the squirrel as I am sure I could seal it well enough to keep it out, but smaller rodents and/or bugs/wasps finding their way in through such a convenient opening if I leave any space at all.