Tread Depth Commercial Building-How is it measured??

[liarchitect]

in an non-accessible fire stair where or how is the tread depth measured? is it from riser to riser

for example if the riser to riser dimension is 9.5"+1.5" nosing=11" ?

or

is it required to be

11" riser to riser + 1.5" nosing for a min tread depth of 12.5"

as per section 1009.3 (IBC) Building Code of New York State 2007

1009.3 Stair treads and risers. Stair riser heights shall be 7 inches (178 mm) maximum and 4 inches (102 mm) minimum. Stair tread depths shall be 11 inches (279 mm) minimum. The riser height shall be measured vertically between the leading edges of adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 0.375 inch (9.5 mm). The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at right angle to the tread's leading edge.

in section 1009.3.2

leading edge is defined as

1009.3.2 Profile. The radius of curvature at the leading edge of the tread shall be not greater than 0.5 inch (12.7 mm). Beveling of nosings shall not exceed 0.5 inch (12.7 mm). Risers shall be solid and vertical or sloped from the underside of the leading edge of the tread above at an angle not more than 30 degrees (0.52 rad) from the vertical. The leading edge (nosings) of treads shall project not more than 1.25 inches (32 mm) beyond the tread below and all projections of the leading edges shall be of uniform size, including the leading edge of the floor at the top of a flight.

 

[fatboy]

Tread depth is measured nose-to-nose.

 

[Examiner]

Tread is 11" min per Code and then you can add the nosing. As fatboy stated "nose to nose" will be 11" and nose to back of point of tread will be 11" plus the designed nosing. The Code Commentary shows this graphically Fig 1009.3.(1) & (2).

 

[TJacobs]

Get a framing square, set the blade (wide end) on the tread so the tongue is upright, bump the tongue (narrow end) against the nosing of the next tread and read the measurement on the blade.

 

[Architect1281]

Yu measuh stares this weigh

I seriously hope you are not a registered architect asking this question but a (liar ca tect)

The Stair measuring guide for dummies is

MEASURE WITH A FRAMING SQUARE !!!!!

thank heaves for TJacobs it is the only way

as a Architect of long standing it is one of the tools beside my computer

all the answeres to framing questions are printed right on it

buy a good one and learn to read it

 

[mtlogcabin]

Simple questions require simple answers and no more

 

[Plans Approver]

Get a copy of the code and the Commentary.06 IBC 1009.3 "The tread depth shall be measuredhorizontally between the vertical planes of the foremost projectionof adjacent treads and at a right angle to the tread’s leadingedge."from the Commentary: View attachment 347

View attachment 148

View attachment 148

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