Residential Light Requirement and Standards for Stairs - IRC 303.

[Mastermatrix]

R303.7 Interior stairway illumination.​

Interior stairways shall be provided with an artificial light source to illuminate the landings and treads. The light source shall be capable of illuminating treads and landings to levels of not less than 1 foot-candle (11 lux) as measured at the center of treads and landings. There shall be a wall switch at each floor level to control the light source where the stairway has six or more risers.

I have seen many posts discussing the need to measure illumination at a height above grade (usually 30", a meter, or 3 feet), most commonly in the commercial context. However, given the language in R303.7, and other ICC codes (IBC 1008.2.1 and 1205.4), it indicates that the measurement should be taken at the walking surface on stairs in the residential context.

I have discussed this at length with other professionals in my area, and I have not received a consensus on where a luminometer should be placed and how the test should be conducted. Does anyone here have any insight?

 

[rc/retired]

Unfortunately, the only advice I have is for you to contact ICC since they made the requirement.
Good luck!

Ron

 

[d0nut]

Since the requirement is for not less than 1fc at the center of the stair treads and landings, you would need to measure the illuminance at the center of the stair treads and landings. To ensure you met the requirement, you would need to place an illuminance meter on each stair tread and landing, in the center, and take a measurement after verifying that you are not accidentally shading the meter. Each measurement would need to read at least 1fc.

The measurements that are taken at 30" AFF are to measure the illuminance at the workplane where the tasks are occurring, such as on a desk. In this case, the requirement is for illuminance on the surface, so you have to measure at the surface.