u/Dracon_ian

We recently removed a gas fire and wanting to board up the space, with a vent for moisture.

Seeing other people's posts, I'm now worried I've created an issue using the wrong bricks or mortar, and that it's going to expand and create structural issues.

(as far as I could tell, it's holding no weight, it's just filled an empty space, goes up to the lintel above)

Do I need to chip it out?