We have a French door off the living room that leads to a covered porch with a concrete slab. The door threshold is 10-1/2" above the slab, enough that some type of step is required.

We are thinking of putting a precast concrete single step.

See pics here: https://www.dropbox.com/sh/0nbgg655bd7bbbi/AAAzOvCP2nEX0885UR3UneRsa

Questions:

1) I know 10" is kind of an odd size, since a standard riser seems to be 7". So, should we try and make the step 7" off the slab and have a 3" step down from the threshold? Or should we have a 7" step down to the first step, and then a 3" step down to the slab? Or should we split the difference and make two 5" risers? (I am not sure I will have a choice if the precast steps only come in standard riser sizes.)

2. What about width? The door opening itself is 3'. The other half of the door is fixed. Should we make the step 3', 4' or 5' wide? Or the width of the entire door for symmetry?

Anybody with experience with this? Your inputs greatly appreciated!