I would like to re-point my foundation. It certainly appears that I have sandstone foundation blocks (could this be?) as any aggravation of the "mortar" simply results in sandy crumbling to where I'm not sure the blocks themselves won't disintegrate. Can this happen? What can be done? I have been afraid to touch the walls but something must be done. As you may imagine, there is water seeping through the lower "mortar" gaps.