Residential Stair Design – Guidelines, Criteria and Dimensions

by Sean O'Hara on April 15, 2017

I received a question about stair width from one of our clients and thought it made sense to clarify the typical stair design rules for houses. These are the rules that are in the 2006 International Residential Code.

Stairways have to be at least 36″ clear width above the handrail height. Handrails can’t project more than 4.5″ into each side.

You need at least 80″ of head height throughout the stair.

The maximum height of a riser is 7.75″ and the treads have to be at least 10″ deep. Treads also need to be a minimum of 4″ tall.

If you have winders they can’t be shallower than 6″ and they have to be at least 10″ deep when you’re 12″ into the winder.

The landings must be at least as deep as the stairs are wide and you can’t go up more than 12′ without a landing.

Handrails have to be mounted between 34″ and 38″ above the tread nosing and must run the full length of the stairs. The handrails have to be at least 1.5″ off the wall and where they are circular they need to be 1.25″ to 2″ in diameter. If the handrail isn’t circular it needs to have a perimeter between 4″ and 6.25″ with a maximum cross section of 2.25″.

There are a number of other rules for particular situations but these are the general guidelines. There are more difficult stair and handrail rules for commercial and multifamily dwellings. I’ve also written a separate post for spiral stairs.

Originally posted 2008-09-29 17:01:01. Republished by Blog Post Promoter


{ 6 comments… read them below or add one }

Sean O'Hara May 15, 2015 at 2:28 pm

Hi J, I’m not sure where the claim was made that I’m a genius, perhaps it was my mother. But seriously, you have discovered a typo in the code but in the full code is also has in quotations “(2-percent slope)” so that would stand to clarify and any code official would ignore the typo.

After rereading, I should also clarify that I’m assuming its a standard tread. If it is 3/4″ in 3′ then its in the 1/4″ per foot range.

Good eyes – Sean

J May 7, 2015 at 8:13 am

I realize this thread is ancient, but I happened across it yesterday. Sean O’Hara is no genius. “The walking surface of treads and landings of stairways shall be sloped no steeper than one unit vertical in 48 inches horizontal.” can’t be interpreted as he indicates. “One unit vertical” could mean a meter, an inch, a millimeter, or a nanometer, and per 48″, that could be like walking up a wall or walking across a basically flat surface.

Sean O'Hara June 24, 2011 at 9:06 am

The clear space at the top or bottom of residential stairs can be part of a hallway.

Francisco Valenzuela June 20, 2011 at 5:11 pm

In a residential situation, can the landing be a hallway? That is, can the stairway end like a room door into a hall way as long as the hallway is as wide as the stairs?

Sean O'Hara May 19, 2011 at 1:58 pm

Assuming this is the international residential building code your contractor is 100% wrong. It states “The walking surface of treads and landings of stairways shall be sloped no steeper than one unit vertical in 48 inches horizontal.” In a 12″ deep tread that’s 1/4″ of outslope.

I would advise you to rectify that immediately, in rain and certainly in ice that amount of outslope is very dangerous.

trace May 19, 2011 at 1:04 pm

EV Studio
is there a code for exterior residential concrete stairs as far as the slope of the tread?
my contractor pitched each stair tread 3/4″ each
it feels hard to walk down as your weight leans towards the ball of foot as you walk down
seems excessive to me
is there a min and maxium per boca code i should know before going to city to discuss?
the contractor sdays that it normal of 3/4 inch

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