# Los Angeles CA - Single Family Curved Residential Stairs



## Remington (Jun 13, 2018)

I am designing a curved staircase with a thread depth of 6" at it's smallest point and 11" , 12 inches away from the edge of the 6" edge.  

For Group R-1 occupancy, a Single Family home, do the curved stairs have to meet the curved stairs code requirement as specified below?  It seems ridiculously difficult to comply in a small entry space.  

Curved stairways with winder treads must meet the minimum and maximum tread and riser requirements per Section 1009.4. Specifically, a minimum 11 inch tread depth, measured at a right angle to the tread's leading edge at a point 12 inches in from the side where the treads are narrower, is required; a minimum tread depth of 10 inches is required; and riser heights shall be 4 inches minimum and 7 inches maximum. Also, the smallest radius of the stair shall not be less than twice the required width of the stairway (radius requirements need not be met within Group R-3 occupancy or an individual dwelling unit within Group R-2 occupancy).


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## mark handler (Jun 13, 2018)

Group R-1 occupancy, a Single Family home?
Is it a R-1 zoning designation? Or A R-1 Group per the Building code?
Single Family home per the State code is an R-3 and under the Residential code not the building code.


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## Remington (Jun 13, 2018)

This is an R-1 zoning designation.


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## Remington (Jun 13, 2018)

The single family home is in  R1 zoning


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## mark handler (Jun 13, 2018)

Zoning has nothing to do with the building codes
In CA you are under the Residential Building Codes


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## Remington (Jun 13, 2018)

yes.  I know.  But can a curved stair with 6" min be allowed in a single family home?


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## mark handler (Jun 13, 2018)




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## Pcinspector1 (Jun 13, 2018)

Not on CA code but: 

2012 IBC 1009.12 Spiral stairways- shall have a 7.5-inches minimum clear tread depth at a point 12-inches from the narrow edge. Riser height shall not be more than 9.5-inches.

RESIDENTIAL, 2012 IRC R311.7.10.1 Spiral stairways- 7.5-inch minimum tread depth @ 12-inches from the narrower edge. All treads to be identical and rise to be no higher than 9.5-inches.

Both require a minimum of 26-inches clear width above and below the handrail. Head room can be 78-inches.

Sooo... at the narrow end, 6-inches is too small  

That's what she said!


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## Pcinspector1 (Jun 13, 2018)

I did't know this was referencing winder treads, R311.7.5.2.1, 6-inches is allowed at any point within the clear width of the stairs. Poster said curved stair, my mistake.

Nice reference, MH


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