Rules for stairs
1. TREADS (STEPS)
Depth
The tread depth (run) of staircase have to be measured from left side or inner:
- at 50 cm if wide is <=1 m and
- at 60 cm if wide is > 1m
It has to be 10" to 12"; Recommended 11" (25.4 to 30.48 cm; Recommended 27.94 cm)
Source:
https://inspectapedia.com/Stairs/Ideal-Stair-Design-Specifications.php
Treads depth for winder stairs turn
Winder treads shall have a minimum tread depth of 10 inches (254 mm) measured at a point 12 inches (305) mm from the side where the treads are narrower.
Winder treads shall have a minimum tread depth of 6 inches (152 mm) at any point.
Within any flight of stairs, the greatest winder tread depth at the 12 inch (305 mm) walk line shall not exceed the smallest by more than 3/8 inch (9.5 mm).
Source:
https://inspectapedia.com/Stairs/Stair_Winders.php
Treads count for squared spiral
"Calculation of the stairs with a pivoting steps of 90°.
In my experience the best is 3 steps with a width of 80 cm.
More - steps will be too narrow and so uncomfortable."
Source:
https://www.zhitov.com/en/lestnica3/
* * For me, at a 90° winder stairs turn, it appear too restrictive.
* * Probably they have right considering the safety rules but ...
* ** So, for square spiral stair I'll use the measure of walk line at 50 cm.
* ** The measure have to start from pole (excluded)
* ** For uniformity variation I'll use 1.0 cm.
Tread hight (Step rise)
For a staircase it have to be 4" to 8.25". Recommended 7"
Source:
https://inspectapedia.com/Stairs/Ideal-Stair-Design-Specifications.php
That mean 10.16~20.955 cm. Recommended 17.78 cm
* **I've used some rounded values:10.2, 17.8, 21.0 cm
Tread offset (nosing)
For a staircase is required!
It have to be 1" to 1.1/2" projection beyond the riser face
Source:
https://inspectapedia.com/Stairs/Ideal-Stair-Design-Specifications.php
Nosing overlaps must be at least 16mm
Source:
https://www.pearstairs.co.uk/staircase-buillding-regulations/
Projection: The nosing must project between 3/4 inch (19 mm) and 1 1/4 inches (32 mm).
This ensures the nosing provides enough of an extended stepping surface.
Source:
https://www.homebuildingandrepairs.com/codes/stair/shaping_tread_nosing.html
* ** I'll use 1.6~3.2 cm optimum 2.5 cm
Stairs Width
For a staircase wider than 1.8 m, a balustrade is required in the middle
Source:
https://inspectapedia.com/Stairs/Ideal-Stair-Design-Specifications.php
Minimum Distance Between Two Railings — Under 30â€
Source:
https://grecorailings.com/five-international-...ed-to-know-for-handrails/
Handrail IBC Code Requirement
1: Handrail Height — 34â€- 38â€
2: Handrail Diameter — 1.25†– 2â€
If the handrail isn’t circular, the perimeter dimension should not be less than 4 inches and mustn’t be greater than 6.25 inches.
The maximum and minimum cross-sectional dimension should be 2.25 inches and 1 inch, respectively.
A minimum radius of 0.01 inches is required for the edges.
3: Minimum Hand Clearance — Not Less Than 1.5†(3.81 or ~4.0 cm)
4: Maximum Projection of Railing — 4.5†(11.4 cm)
“Projections into the required width of aisles, stairways, and ramps at each side shall not exceed 4.5 inches (114 mm) at or below the handrail height.â€
5: Minimum Distance Between Two Railings — Under 30â€
Source:
https://grecorailings.com/five-international-...ed-to-know-for-handrails/
* ** I'll use: 86.4 to 96.5 cm with optim 91.44 (36")
Handrail 2010 ADA Standards Code Requirement
505.7.1 Circular Cross Section Handrail
* shall have an outside diameter of 1.25" (32 mm) minimum and 2" (51 mm) maximum.
505.7.2 Non-Circular Cross Sections Handrail
* shall have a perimeter dimension of 4" (100 mm) minimum and 6.25" (160 mm) maximum,
* and a cross-section dimension of 1" (25 mm) minimum and 2.25" (57 mm) maximum.
* A minimum radius of 0.01 inches is required for the edges.
Source:
https://up.codes/s/cross-section
* ** I'll use handrail width range: 3.2 cm to 5.1 cm
Balusters
Regulations stipulate that a 100mm sphere should not be able to pass through any openings between spindles or any other gaps in the handrail, such as between glass panels.
This is to prevent small children from getting their head stuck.
Source:
https://www.pearstairs.co.uk/staircase-buillding-regulations/
Pitch: optimal 7"/11"(Angle: 32.5° or Slope: 64%)
Staircase category according to angle range (from 0° to 90°) or to slope range (from 0% to 380%):
-ramps: angle: 0° to 18°; Preferred: 0° to 7°; slope: 0% to 32%; Preferred: 0% to 12%
-stairs: angle: 18° to 50°; Preferred: 30° to 37°; Optimal: 32° to 33°; Ideally: 32.5°
slope: 32% to 102%; Preferred: 58% to 75%; Optimal: 64%
-ladders: angle: 50° to 90°; slope: 102% to N/A
---stepladders & raised fixed ladders: angle: 50° to 75°; slope: 102% to 373%
---ladder with rungs: angle: 75° to 90°; slope: 373% to N/A
Formula: (Rise / Run ) x 100 = % Slope
Source:
https://inspectapedia.com/Stairs/Ideal-Stair-Design-Specifications.php
Job verdict using angle and comfort
Dmitry Zhitov: „The length of the pitch man is 60 to 66 cm, on average - 63 cm.
Comfortable stairs corresponds to the formula: 2 step height + depth level = 63±3 cm.â€
Source:
https://www.zhitov.com/en/lestnica3/
Francois Blondel formula: g + 2r = 24 inches (60.96 cm so, 61 cm)
24 inches is 610mm, roughly in the middle of the 550mm to 700mm (21³/₄" to 27¹/₂")
Source:
https://www.practicalarchitecture.com/blog/th...f-a-comfortable-staircase
* ** I'll use 55 to 70 cm for Stride length
A new beta version .
Probably this will be the final look even I'm not very satisfied.
I've tried to implement the above set of rules. Some of them not yet.
Not fully functional and many calculus could be false.
Try it with care!!
I'm interested on how it work under MacOS. I don't have the possibility to test.
Few pictures:
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A computer program does what you tell it to do, not what you want it to do. Murphy's Law
When all else fails, read the instructions. Murphy's Law
If you don't like "AS IS", DIY. Dorin's law
