Maximum Stair Tread Thickness

[kiwijbob]

After much searching I am unable to find a code stipulated maximum dimension for the tread thickness, I find it strange as especially with Part 9 open risers if the tread was too think you could get a boot stuck in there!

 

[tmurray]

Nothing that I can think of to prohibit this. My initial though was nosing, but it is not clear enough to prohibit this type of installation.

 

[walker.t]

After much searching I am unable to find a code stipulated maximum dimension for the tread thickness, I find it strange as especially with Part 9 open risers if the tread was too think you could get a boot stuck in there!

Does the code you’re working under have anything to say about maximum nosing projection and treatment of the bottom edge of the nosing? For example, IBC 1011.5.5.1 states a maximum 1.25” nosing projection and A117.1 504.5 states the underside of the projection must be curved or beveled. Limiting the depth and providing a bevel or curve would help prevent a boot from getting stuck.

 

[Inspector Gadget]

As long as you meet the minimum nose-to-nose run, you're fine. I can't say it's smart, but ....

 

[ICE]

I am unable to find a code stipulated maximum dimension for the tread thickness

7" CBC --- 7.25" CRC
In words, there isn't a maximum dimension for a tread thickness other than what's found in your imagination.

 

[kiwijbob]

In our situation we're looking at a 2" tread thickness, just had me wondering what if we went with a 6" thickness with 1" spare below to meet your "nose-to-nose run". No, not smart at all.

 

[mtlogcabin]

open risers if the tread was too think you could get a boot stuck in there!

And if the open riser is more than 4 inches then a child could fall thru or crutches/canes can get tangled in the opening if they slipped.

 

[ICE]

a child could fall thru

I think that it is more about legs.

 

[kiwijbob]

I think that it is more about legs.

Not to go too far down the rabbit hole but the 4" rule I understand is primarily to prevent small kids getting the head stuck, I have three boys.... I've seen it all!!

 

[Inspector Gadget]

Not to go too far down the rabbit hole but the 4" rule I understand is primarily to prevent small kids getting the head stuck, I have three boys.... I've seen it all!!

FYI, some changes coming in NBC 2020. Not sure what BCBC says about open risers...

 

[SCBO1]

I think you could have a 3-inch natural slab as longa as you meet the nosing projection. With that said would your foot get hung up on the underside of the tread as you navigate the stairs? Spiral stairways come to mine. A slab could be router to accommodate a nosing projection IMO.

Might also check with SMA (Stairway Manufactures Assoc.) to see if they have any illustrations.