Hi Joe,
Thanks for your reply. The entire protrusion is OSB extending the living room floor. I put a 20V battery next to the railing to give some perspective of the width.
I have the “top of the stairs” trim kit on order right now along with the stair noses that will fit over my stairs made of 2x material. I will have to see how wide the trim is before I start cutting.
Thanks,
Jessica