With all of the snow we had this past winter in New England some of the tiles have come loose in my Pantry. It appear that as a layer of ice build up on the deck outside and then melted that some of the water worked itís way in through though the threshold and the fascia boards in that general area. None of the ties have broke and at this point only a few are loose.

My question is do I need to retile the entire area or can I ground out the tiles that are loose and a few of the surrounding tiles, clean the surrounding area and reply the tiles?

Also, to prevent water from seeping in again should I put lead sheathing on the inside edging of the threshold?