To help keep your foot from slipping off the back.

ADA requirements include slopeing closed risers to keep you from catching your toe on the overhanging tread.

For safety in going down the stairs. When you step down the stairs, you place the ball and toes of your foot on the tread below and then the heel follows. The nosing provides clearance space for your heel to drop on the tread. If there were no nosing, your heel might hit the riser and you will stumble forward (and probably fall if you are not holding n the handrail).

To encourage tripping as you go up the stairs.

The detail was created by a lawyer-engineer type.

Mike McCann
MMC Engineering

I have a similar case that doesn't appear to be addressed in the codes (specifically Florida Building Code). The nosing is normally 2" or so thick, allowing a vertical space of about 5" for the heel during descent as doct9960 stated.

I have not been able to find this dimension in print anywhere. I'm investigating a trip and fall on a cast concrete stairway in which the nosing is about 5" thick, leaving a vertical space of about 2". Enough for the toe when ascending and enough to catch your heel during descent. Looks really odd like they had the plans/forms inverted when casting the stairs.

Has anyone out there dealt with anything like this? Thanks.

  

slickdeals...also, the nosing provides a visual distinction so that negotiating the stairs, particularly walking down the stairs is easier for some.  Primary reason is to prevent slipping.

GTR1--I'm confused by your dimensions.  The nosing does not have a "thickness".  It is the leading 1-inch of a tread width.  The Florida Building Code references NFPA 101, The Life Safety Code.  That gives the dimensions and requirements for treads, risers, stairs in general, and handrails/guardrails.  The FBC also addresses some of these items and there is some conflict. Check both for your guidance.

NFPA 101,for existing buildings, gives a maximum riser height of 8 inches and a minimum tread width of 9 inches.

In general, the sum of two risers and a tread should be between 24 and 25 inches.  As you can see, if you have two 8-inch risers and a 9 inch tread, you are at 25 inches.

What was the prevailing building code in effect at the time of construction for your project? For the FBC versions 2001 thru 2007, the risers must be between 4 and 7 inches and the minimum tread width is 11 inches.  The 2007 FBC provides some slope tolerances as well (1" in 50")

The nosing also buys you an extra inch.  If the code says you need 11 inch wide treads, this will include the 1" overlap for the nosing, so in essence, your risers will only need to be spaced 10" apart.    

Maybe this photo will help explain the dimensions.

• http://files.engineering.com/getfile.aspx?folder=52089754-85cc-46d2-b207-36

The Kent mall in Lindsay has a deep nosing and when you are going down stairs, the 'little lip' on the heel of your shoe/boot can catch on this and try to pitch you forward.

Dik

dik...sounds like a retirement program with the right lawyer!!

GTR1...what was the prevailing code at the time of construction?

Interesting question...at what point does a nosing become too thick, and stop being a nosing?

I haven't seen any specification for the maximum thickness of the nosing, but some residential stair info is here:

http://www.stairways.org/pdf/2003%20Stair%20IRC%20SCREEN.pdf

OSHA Nosing:

1910.24(f)

"Stair treads." All treads shall be reasonably slip-resistant and the nosings shall be of nonslip finish. Welded bar grating treads without nosings are acceptable providing the leading edge can be readily identified by personnel descending the stairway and provided the tread is serrated or is of definite nonslip design.

 

slickdeals,

Doct9960 answered your question correctly.

GTR1,

I would say the stairs in your photo do not have nosings, so in my opinion, if your code requires nosings, this stair does not comply.  The riser is vertical, only interrupted by a rebate at the bottom.  This rebate is not large enough to serve a purpose in terms of the stair functionality, but I don't believe you will find a code statement to that effect.

Nosings for steel pan and wood stairs are achieved by extending the actual nose beyond the riser by 1" or 1 1/2".  For concrete stairs, it is standard to slope the riser over the full height.

jfudo,

The length of a tread is measured between the same points on adjacent treads.  So the nosing overhang does not "buy you an extra inch".

The construction was approx. 1987 so I'm assuming the applicable code is the 1985 SBC (with updates). There does not appear to be anythig in this code adressing my conditions, however, per the code, treads less than 10" require nosings. Mine are 9.5" not considering the nosings.

The one I was referring to was about 4" deep and had a ceramic tile secured to the 'dropped' portion.

Dik

GTR1...I wouldn't bet on the 1985 SBC being the applicable code.

Depending on where you happen to be, the municipalities generally adopt the code by ordinance, and they often lag way behind.  Check with the building department and find out when the application was made and that will tell you the applicable code.  It could have been the 1982 Code.