Stair Height/Depth

16 years ago

I currently show a 7" rise with an 11" depth on my stairs. Does this seem right??? I want them to be wide, but not abnormal. I think the 7" is ok, but does 11" seem like too much?

John

Featured Answer

mightyanvil

16 years ago

Stair treads must be measured excluding the overlap with the tread above and yes, an 11" tread is the appropriate size for a 7" riser.

There is an ideal ratio between the riser height and the tread depth of a stair that allows climbing to be natural and comfortable. In other words, you don't find yourself leaning forward or backward as you climb. As the riser gets shorter the tread must get longer even though that seems like an inverse ratio.

In a private residence a 7 1/2 to 7 3/4" riser is typical with a tread depth of 10 and 9 1/2" respectively (the shorter riser gets the longer tread). For ideal comfort a 7" riser should have an 11" tread. (In a building accessible to the public a 7" riser is the maximum allowed by code and the tread must be at least 11" for ease of use by the physically disabled.)

If the risers are open and the International Residential Building Code is in effect the vertical space between treads cannot allow a 4" sphere to pass.

Comments (7)

ajpl
16 years ago
The local code probably provides an allowable range. I know ours did but I can't remember it. I ended up with 7 and 5/16 rise and 9.5 run. My current house is 7.5 and 9 and 1/4. Both are open stairs and don't look narrow or cramped. Here's a picture of the new house stairs.
galore2112
16 years ago
Per code (IRC2003, R311.5.3), tread depth has to be a minimum of 10".
For tread depths What's your stair design? Does it have a nosing? If no, then the treads must be >=11" deep.
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mightyanvil
16 years ago
Stairs are not designed by building codes they are merely restricted by those codes.

Here is what I use to design a stair:
mike13
16 years ago
Per code 2006 IRC R311.5.3.2 the minimum tread depth shall be 9 inches. Also, there can be no variance of 3/8" between the treads within a flight of stairs.
mightyanvil
16 years ago
Many jurisdictions use one of the earlier IRC editions which require the min. tread depth to be 10" and some jurisdictions that have adopted the 2006 edition have revised it to be the same as those earlier codes.
carterinms
16 years ago
I found this document on-line and used it to design our stairs.

Here is a link that might be useful: stairways.org IRC