Who is right. The county or IRC

I discovered today that my county has stated by the IRC [311.5.3.2] that min tread deapth is 9 in. My resources say 10 in. :shock: WHo is right?

The IRC is what my town uses too. It has always been nine inches as long as I remember. What ever the code is for that area, I use as my reference. There is not much county codes where I am at.

IRC2006 R311.5.3.2: The minimum tread depth shall be 10 inches (254mm). In IRC2009 reference R311.7.4.2

10 inches plus 3/4 to 1 1/4 for the nose

Tread depth is defined to be from nosing to vertical riser.
10" for residential and 11" for Commercial.
That converts to a 9" run for residential and a 10" run for commercial.

And so was the 2003 IRC;

Wikipedia= Tread - the part of the stairway that is stepped on. It is constructed to the same specifications (thickness) as any other flooring. The tread “depth” is measured from the outer edge of the step to the vertical “riser” between steps. The “width” is measured from one side to the other.




Thanks Marcel,
There you have it. You guys can quit guessing now.:stuck_out_tongue:

My town uses IRC 2000 the last time I checked. I still would not argue with the county on that, because you would just lose. Most of our steps uses a 2X10 as a thread which is 9 1/4" wide in my area. The city and the counties pass them everytime.

Thanks for straighting that out.

2006 IRC R311.5.3.2
The minimum tread depth shall be 10 inches. The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the treads leading edge.

States, counties and cities use “model” codes for just that purpose - models. They have the authority to change any code or portion of a code as they feel fit.

The code that counts, is the one being used by the specific municipality.

Jeff is the winner! After chatting with one of the county code guys, he said they changed it when the adopeted the rule. I guess thats why we do not quote codes. Every county, city, or jurisdiciton is different.

The AHJ is the final word.

When your code book collides with the county, your code book is a Mazda and your county is an 18-wheeler.


Thanks Jeff, I assummed that was a given.
You are absolutely correct, and In my case, no changes are made.:slight_smile:


As another example… while most of the state of Ohio has required minimum R38 insulation in ceilings for some time, they have recently adopted the R49 requirement now. Some local jurisdictions still allow minimum R30 however… a few code revisions back.

It pays to understand your local municipalities and do some research. They do have final say.

Stop being such a picky guy lololol. Dang deal killer!