Vertical Dimensions and Stair Parameters Check

jeff2013July 20, 2013

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

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Repost the drawing without the overlaid image from the architect. Hope this reads better.

    Bookmark   July 20, 2013 at 6:21PM
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This is the floor plan from the architect. There are at least 5 exterior walls from 2nd floor (over interior sections of the main floor footprint ) needing support beams.

    Bookmark   July 20, 2013 at 6:47PM
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1. The floor thickness (if that is what it is) has no relevance to the stair design.

2. Both suggested designs would feel awkward by making you lean forward as you climb which is especially difficult for children and the elderly.
The 7.5 riser should have a 10 tread
The 7.125 riser should have a 10.5 tread
A 1 inch nosing should be added to each tread but it is not part of the stair run calculation.

3. The winder as drawn is dangerous and a code violation. The narrow end usually must be a min of 5 inches so it rarely saves space but it can change where the stair starts and stops.

The landing should be the same width as the largest stair treads and the stair should not decrease in width as it decends because it is an egress path and also the primary access for furniture moving.

The clear dimension from the stair to the wall at the 1st floor should be larger than 38 inches. The double tread return seems excessive for the space.

    Bookmark   July 20, 2013 at 7:50PM
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Thank you for your response! This is very helpful.

1. Floor thickness.
I have no clue about the appropriate floor thickness (the space between first ceiling to 2nd ground). However, I do need certain ceiling height, say no less than 9ft. I understand that we do need to figure out the total floor to floor height (ceiling height plus floor thickness) as the total staircase rise. Right? Or do you mean that we shall go the other way around, let the whatever staircase total rise dedicate the ceiling and floor spacing arrangement?

2. Riser/Thread Sizes
We are expecting a baby soon and yes, we are not getting younger each passing day. So I am concerned about any potential safefy issues.

With the given footprint of 15' 4.5" by 7'6", I hope we have enough space for the required run and width to reach the desired floor to floor height of 142 (or 142.5 in my calculation) suggested by the architect. I am trying to use the smaller riser option (7 1/8" riser and 10.5" tread with 1" noser) to see if we can get it work. Let me know if you have any other options in mind.

3. Winder/Landing
I am not sure if my previous drawing was clear so I am attaching another picture. You can tell that the winder (thread #12 orange) is a trapzoid. The minimum width is 12inches, same as a standard tread depth. So clearly it was there not for saving any space but as a 'design' feature on purpose.

Is that acceptbable now? Or you sill suggest that the landing (tread #13 green) shall always be square or two squrares together at the U turn?

4. Clearance / Curved Threads
I have indicatd the 38" minimum clearance line on the first floor last step. It looks to me there maybe a problem with the door to coats.

The architect was trying to put the the curved stair steps as the focal point in the foyer. It may look nice but if there is any safey concern, we shall have just one step sticking out to the foyer/great room.

Again, the reduced tread depth shall let us have enough risers with reduced number of treads and that shall help the clearane issue.

This post was edited by jeff2013 on Sat, Jul 20, 13 at 22:01

    Bookmark   July 20, 2013 at 9:57PM
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I have no way of knowing how thick the floor should be.

The single winder is terribly dangerous and creates a strange handrail. If you want winders they should fill the space and be of equal size. Odd features don't belong in the middle of a stairway. if you are concerned about safety don't use winders of any kind.

The IRC requires that "the width of each landing shall be not less than the width of the stair served." That means the landing must be 4-1 instead of 3-4. It is also necessary to be able to move furniture.

The curved steps are fine but it is a big feature so it needs adequate space.

    Bookmark   July 20, 2013 at 11:01PM
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Location of the "winder" riser is a terrible design and safety hazard. Probably doesn't meet code either. It would be much better to simply make all the treads and risers identical. You apparently don't need a winder.

If it was me, I'd eliminate the curved stairs closest to the small hall closet and maintain maximum corridor clearance there. The curved stairs which die into the wall are fine if a "design" feature is desired.

Good luck with your project.

    Bookmark   July 20, 2013 at 11:02PM
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For a riser of 7.125 the treads could be as large as 10.75. The formula I use is T=20-(4R/3) which is recommended by the AIA graphic standards.

The riser numbering appears incorrect. Are you aware that the landing is just below the ceiling? You don't show the floor opening above so it is not clear how this works.

As for the floor thickness, that should have been settled before the stair had been drawn in plan. Ducts are usually in the basement or attic not in the first floor ceiling and when they are they fit between the joists or are shallow. If this is still being designed you should postpone the stair design.

This post was edited by Renovator8 on Sun, Jul 21, 13 at 8:00

    Bookmark   July 21, 2013 at 7:55AM
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Renovator and Virgilcarter,

We will get rid of the single winder in the middle and make both flights of equal width of 3-9. I am still looking at different riser/tread options from 7.5/10 to 7 1/8 / 10.75.

I am inclined to keep the curve stairs if there is adequate clearance. I am thinking of using a smaller closet door (from 30" to 24" door size) and/or steal some space from the HVAC clozet (from 42" to 36" depth) and shift the coat closet left.

BTW, I just received the first set of the elevations from the architec and I will post them separately. Please take a look and let me know what you think. Thanks! Jf

    Bookmark   July 22, 2013 at 1:03AM
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