Quote Originally Posted by rustynail View Post
Anglegrind a groove about 4mm deep along the front edge of door. Then grooves running from this cut to the outside edge of slab at about 200mm spacings. Make sure the short cuts are deeper at the outside edge to give run off (say about 10mm.) If water still comes in you may need to increase the number of short cuts to 100mm spacing. Normally 200mm is enough. Use a straight edge as a guide for the long cut at the door and keep the short outer cuts square to the long cut and it will all look like it was meant to be.
Hope this helps.
Grooves will quickly fill up with "gunk"