Re: Proper Patio to door threshold distance
A 3" to 4" step down from the house is not a bad thing and you'll be certain not to have issues with the threshold support or leakage. If you've got good overhangs on the protected side of the house, then you can get away with coming up under the threshold and maintaining a good pitch to the concrete of at least 1/4" per foot. If you install a felt expansion joint between the slab and the wall of the house, all the better, as it will promote drainage and alleviate possible leak issues.
I would suggest setting the level of the slab at the same level as the ground (base of the grass blade where it protrudes ) at the grass. This way you simply put one wheel of the lawn mower on the edge of the patio and mow, otherwise you'll have to finish up with a string trimmer all the time which gets monotonous. Of course, depending on the difference between the threshold and the grass level, you may not have a choice to be higher.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!