How would I simulate a wall being made up of a bunch of parts, as I don't want the game to lag

Actually having the wall being made of a bunch of parts would make the game horribly optimized, but I want to be able to explode walls and not destroy the whole wall but only them few parts where the damage may of occured. I also want to know how would i get that original part of the wall to disappear, possibly with a union? I don’t know