Vertical Dimensions and Stair Parameters Check
I have another post on floor plans but this is something related to the third dimension so I am starting a new post.
What I I had in my original plan includes
1. Floor heights. 10/2/9
First floor to ceiling 10ft; 1st ceiling to 2nd floor spacing 2ft; Second floor to ceiling 9ft.
2. Staircase. 6 7/8" / 10.5"/20
Riser=6 7/8"; Tread=10.5"; 20 treads or 21 risers to reach a total 12' 3/8".
The latest design from the architect has
1. Floor heights 9/2-10/8
A. First floor to ceiling mostly 9ft. Maybe lower in some areas due to ducts. As the great room (maybe in dining too) has vaulted ceiling, this looks good to me.
B. Floor spacing 2ft 10 inches. There would be 2 x 12 joists and then the duct runs. Not sure if this has anything to do with the many support beams for 2nd floor walls, but my impression is that most floor spacing is 1ft to 2ft. Is it excessive or any problem here?
C. Second floor ceiling 8ft. I was told that it can go to 9ft but that would change some proportions. Not sure what exactly that means. I was told that the ceilings can start from low and then getting higher in the middle to make the rooms feel bigger. Maybe that is OK.
2. Staircase 7.5" / 12" / 18
A. Riser of 7 1/2 inches. This is on the high side but is OK by itself (as I am concerned with the little kid climbing up the stairs).
B. Tread of 12". The foot depth is ideal by itself and together with the 7.5 riser it will make the stair not that steep.
My question is the combination of 7.5/12 looks too big if I combine the two numbers using some formula I found on this forum or elsewhere. That means we may need to make efforts to make bigger step/gait/stride size effort to climb up and down. I am not sure how big the problem is.
C. The 18 treads or 19 risers would bring the floor to floor height of 11'10.5".
My proposal is to use 7 1/8" riser, 11"tread, and 19 treads (20 risers) to bring the floor to floor height of exactly the same 142.5 inches or 11'10.5". And I can do it over within a slightly smaller floorrpint for the staircase, which will help a little bit on the clearance at the entries on both floors.
I have another question regarding the winder tread (27.5 degree slanted). I know if may provide an interesting design feature of more open view to the great room. But I am concerned if there is any safety issue here.
In summary, I have 3 questions here
Q1. Is 2ft10 inches floor spacing excessive?
Q2. Is the 7.5 riser 12 tread combination good? Or would 7 1/8 riser and 11 tread better? Or any other 'optimal' design here?
Q3. Is the winder OK? Or we shall better have a simple straight landing?
Attached is the drawing showing the current staircase design.
Sorry for writing so long. Thanks for your help. Jf