I am finishing my basement. I am replacing an exisitng sliding glass door, it goes to an outside concrete stairwell. I will have 3/4 inch slate floor on the outside concrete floor (3ft x 5ft) and engineered wood inside, on top of a 3/4 inch subfloor. Do I raise the area under the door sill so it is even with the inside floor? How do I raise it? Thanks.

Not sure what your question is. Is it can I or is it should I?
Why would you want to raise it. Is it because the slate outside is higher than the bottom track. Are you saying you have a concrete floor with 3/4" plywood on it and then engineered flooring on top of that?

You can raise by putting treated plywood under the bottom track if you have enough head room, which I doubt.

Hi, thank you for your reply. Question is "should I" raise it? Outside slate flooring is not down yet, I'm planning for it. Inside basement concrete floor will have DRIcore on it (7/8") and then engineered flooring on top of that. I have about 6 inches of head room in existing poured concrete wall opening above existing door, it was cut that way to begin with. I want to prevent water from coming in if I raise it with treated plywood or treated 1x4 -- glue that down and silicone caulk the beams? Or is what I am doing just not necessary?

If the sub floor and engineered flooring measure less then height of bottom track, you are good. Install door and butt to it. Be sure existing area for sill is level.

Chuck

Sounds like the interior floor will be at or above the top edge of the bottom door track. Also sounds like the slate on exterior would raise the track up to an appropriate height. Why not just install the slate on the exterior running it under the track? Seal between the slate and the interior floor with silicone. Seal under the track with silicone.