Quote:I'm going to go with this.
For my records: the cut in the stairs for the second tread is 13.25" and the tread is 1"
By replacing the tread with 3/4" subfloor (actually 23/32 most likely) and 3/8 engineered flooring, but actual final riser height (outside the theater) will be 14 3/8" (minus 1/32) That makes it withing 1/8 of the original tread, so it's consistent with the staircase from the kitchen. That will also make it easy to have any other steps I build match up.
To make this happen, the first layer of 3/4 subfloor needs to sit, as Tim shows, 3/4 below that tread, or 12 1/8 above the existing flooring.
To make up the difference between 11.5 (one 2x12) and 12 1/8, I think I'll go with the joist isolators. They should bring up the joist by almost 1/2 (15/32), leaving just over 1/8. Either that won't matter, or I'll shave down the stair framing by 1/8". In either case, it's an upgrade all around.
This mundane conversation has been brought to you by the letter A, N, A, and L, and the numbers 15/32 and 23/32.
(EDIT: Well, the sharpest and most experienced builders among you may have noticed - this was a wasted mathematical exercise, since a 2x12 is 11.25 inches wide, not 11.5. Turns out, I think, anything nominal 8" and wider is 3/4 inch different, while 4" and 6" are 1/2 different. What a system we have.)
Ultimately, I have decided (months later) to use 3 layers of the 23/32 tongue and groove subfloor, atop the 2x12.
Edited by HopefulFred - 8/25/13 at 3:40pm