Considering installing french drain inside of basement. The slab is 2" thick and the walls are block. Al of the articles, research etc... I have read have said to cut the slab about 12-18" from the block wall install the piping and reconcrete over everything but leave a small gap next to the block wall. Does the slab provide any significant reinforcement since the block wall will now not be touching the slab. This tiny gap is ok? Thanks.