# Optimizing tread depth, riser height, and tread nosing projection for a compact staircase

I live in Indonesia. There is no building code. No insurance. No liability.

Although building codes etc. might say 30cm run, 20cm rise, in practice one can find products such as these, with thousands sold on eBay:

The specs given are similar:

Fixed stair at 57° climb Stair Width - 545mm Stair Width (Inc Handrail) - 572mm Tread Dimensions - Thickness: 27mm Depth: 142mm Width: 491mm

String Dimensions - Thickness: 27mm Depth: 142mm Length: 3340mm

Height 2.835m and 1.745m run

I.e. typically 60cm total width, around 55cm wide for the treads, typically 14cm tread depth and rise of between 20cm and 23cm.

The question is even though we assume these don't meet any building codes, what can we say with regard to the following with regards to such a steep staircase:

1. is it a bad idea to have nosing (e.g., you could make deeper stairs but have them overlap by some amount more than what I believe is the maximum of around 1")?
2. for some reason the tread depth of 14cm seems fairly common, such that I found stairs with 20cm rise and 23cm+ rise, both with the same depth. Is there any reason this should be so? Logically shorter people might prefer less rise and less depth, whereas taller people might want more depth and bigger rise. However, logically is there any determining factor if one is making such a set of stairs from scratch? E.g. if you have 2.5m total rise, then you could make 12 steps with 20.8cm rise, or 11 steps with 22.7cm. Given 2.1m of total run, the 12 steps would then imply 17.5cm deep treads, and the 11 steps 19.0cm. Obviously none of the options are accessible, compliant, etc., but there should be some way to determine which option is better or worse
• You can do whatever you want, but as soon as it gets seen by an inspector/agent(building, fire, insurance), good chance of you getting told to remove/fix it now, if it does not meet code. Local code is what they go by, not code where product/plans are made. People can more easily win larger suits against you if not code. Jul 1 at 20:37
• In the realm of "ship's ladders", the opinion of the users is the overriding factor. Build it to what you and yours prefer. There's no clear answer here. Jul 2 at 15:01
• And you do have liability for the safety of your users, if only of the moral variety. :) Jul 2 at 15:11
• This is defined by OSHA as a 'standard staircase', not a 'ship's ladder', as the angle is (just) less than 50 degrees. There seem to be a number of studies suggesting certain factors: researchgate.net/publication/… researchgate.net/publication/… suggests that tread depth is more important than rise, for descending stairs (noted as the larger cause of accidents) Jul 2 at 16:15

https://www.blog.stairwayshop.com/blog/compact-stairs-code-compliant

https://blog.buildllc.com/2016/08/art-of-the-nonconforming-stairs/

These may be usable if:

• This is an improvement over what you had before. (Which was presumably grandfathered in.)
• This is a replacement for a similar staircase.
• You don't plan on selling (or are willing to redo it properly before you sell.)
• You are building a "tiny house".
• It is an access to an area under 200 square feet. (In some areas.)
• You are not putting it in a residential building.

Building codes are for traditional staircases. I have had many many many flips (and wish I had pictures but didn't think about the future of answering questions on SE) and what I have done with stairs... when I can to save space and get around "code" is to use a spiral staircase.

There are many sites that you can order from like this or you can just look on craigslist. I have bought mine for around 1000-1500 USD green.

Just reading your question and seeing what's new I found this bad boy for around 600 USD... got to think outside the box.

• thanks; I am in Indonesia and we get everything fabricated or constructed, so I'm looking for examples for how to get it done than a specific product. Spiral staircases are definitely a good choice for space saving, it depends on the space though - they require more diameter (42" in your case versus maybe 24" or less for a straight stair case), but probably don't take as much floor space in total Jul 2 at 8:28
• Keep in mind @thelawnet that if this is your only access to the upper floor, moving items up & down is a royal pain! I once moved into a 3rd floor bedroom with only spiral staircases. I had to enlist the help of my roommates as we passed my mattress & dresser straight up the side of the staircase as it was literally impossible to carry anything larger than a box up the stairs. Jul 2 at 12:50
• @FreeMan - agreed somewhat but what you can put through these is more about how big the opening at the top is. Jul 4 at 3:43
• Big, long items, @DMoore won't have enough give to make it around the spiral, no matter how big the opening is at the end. :/ Jul 6 at 11:22
• @FreeMan - not true. You don't have to use the stairs to move things that big up and down you can just use what's left of the opening. We installed a 3 floor spiral in france a few years ago and left one side open - with rail of course - and that three feet open let us bring up whatever we needed... furniture, mattresses Jul 6 at 18:26

user3757614 has pointed to a source of the answer, which is

https://codes.iccsafe.org/content/IRC2018/appendix-q-tiny-houses

This specifies for 'tiny houses' (though this doesn't matter in my case as no building code is applicable, so whether my house is tiny or not is moot):

• risers must be between 7" (178mm) and 12" (305mm)

Then either:

• tread depth is 20" (508mm) minus 4/3 riser height OR
• riser height is 15" (381mm) minus 3/4 tread depth

PLUS:

there is an additional requirement for a landing platform if the ceiling height is lower than 6'2".

Also I found:

https://codes.iccsafe.org/content/IRC2018/chapter-3-building-planning#IRC2018_Pt03_Ch03_SecR311

which specifies:

• alternating tread stairs can be used to access a mezzanine
• ships ladders can be used to access a mezzanine of less than 200 square feet, but they must have handrails on both sides
• a ships ladder must have a maximum rise of 9 1/2", and a projected (with nosing) depth of 8 1/2", and depth of at least 5"

A ships ladder I found here:

with some examples, I think not all are compliant.

Anyway, by reference to the Appendix Q, with my 2.5m rise, and a rise between 178mm and 305mm this means you could use between 9 and 14 stairs, as such:

• 9 stairs = 27.8cm rise, 13.8cm depth, 1.24m run
• 10 stairs = 25cm rise, 17.5cm depth, 1.75m run
• 11 stairs = 22.7cm rise, 20.5cm depth, 2.25m run
• 12 stairs = 20.8cm rise, 23.0cm depth, 2.76m run
• 13 stairs = 19.2cm rise, 25.2cm depth, 3.27m run
• 14 stairs = 17.9cm rise, 27.0 depth, 3.78m run

For some reason it doesn't specify anything about tread projection. Also you can see it results in quite big differences in run; if you take the 11 stairs example and divide it by the desired 2.1m run, you get 19.1cm tread depth, which seems better than a shorter staircase.

I’m an American, so I don’t know anything about metric. You’ll have to convert for me. (Also, I don’t know if our codes match your codes.) This information is for “living spaces”, so stairs to mechanical rooms, storage rooms, etc. would not require these standards.

The maximum rise of steps is 8”. The maximum difference between risers is 3/8” from smallest to largest. (See ICC R311.5.3.1)

The minimum tread depth is 9”. The greatest difference from smallest to largest is 3/8”. (See ICC R311.5.3.2)

A handrail is required if there are 4 or more risers. The handrail is to be installed a minimum of 34” and not to exceed 38” (See ICC R311.5.6)

A landing is required if there is a door at the top and the door swings outward, except for screen doors. The landing is to be the width of the door and 36” in the direction of travel. (See ICC R311.4.3.)

Handrails are required on one side only. (See ICC 1009.15) It’s customary to have it on the right side descending, but not mandatory.

Handrails are not required if there are 3 risers or less. (See ICC 1009.15.4)

Handrails are required to be a uniform height between 34” and 38” above the nosing. (See ICC 1012.2)

Also, the “ladder” you show (that’s not a stair) is illegal because it needs a guardrail so nothing larger than a 4” diameter object can pass through.

Creating something dangerous is silly just because it “fits” in the allotted space.

It is a bad idea to have those. There are building codes and OSHA requirements (in USA) for stair design. Sure, thousands sold on Ebay but there are also thousands of non approved electrical fixtures and switches sold there too. Insurance companies can deny claims if non compliant devices are found in the homes. If you knowingly install them you could be in big trouble. Worse that that, family members could seriously be injured.