Stair tread minimum thickness

[Sean Rainaldi]

Hi,

I am building a new stairway into our basement at our home here in Michigan, the old stringers got rotted out due to some water damage and the stair treads have a crummy linoleum tile.

I checked all the local codes and have all required dimensions except one I can't seem to find. The actual thickness of the stair tread.

The stair case is 36" wide. I will build the new stringers out of 2x12 pine.

The old stair treads are just garden variety pine 1.5" thick cut from 2x10". I would like to build the new staircase using white oak treads - would 3/4" or 7/8" thick treads in white oak with two stringers be sufficient? Or would I need either 1" or greater thickness or an additional stringer for less than 1" thick oak treads?

[Joe Chritz]

If you are not going to cap some kind of existing sub tread then you really want to go as thick as possible. 3/4 is not enough, 7/8 is likely still way to thin unless you have a third center stringer.

Personally I would probably shoot for 1 1/8" minimum but would likely get 6/4 and machine it to as thick as possible.

Make a test piece, support it on the ends and stand on it. You will be surprised how much flex there is until you reach a certain thickness.

Joe

[Gene Howe]

With two stringers, each close to the end of the tread, I'd prefer 1" to 1 1/2".
Of course, this would depend on the tread material. in solid oak, 1" would be just sufficient.
If possible, why not use a middle stringer? In which case, 3/4" hardwood would be fine.
For utility steps, I always use two pieces of 2 by material separated by an 8th to a quarter. But then, I'm cheap and lazy.

[Sean Rainaldi]

Ok thanks to you both.

Also the existing stairs there two stringers made of it appears 2 x 10's. Do you recommend 2 x 12" instead?

Strange thing is, I am reading the michigan building code right now on stringers and risers, and although there is much data I can not find anything in the code which specifies tread thickness and whether to use two or three risers for what ever thickness - unless I am looking in the wrong place?

[Sean Rainaldi]

Another option I could use, I have plenty of left over 3/4" tongue and groove white oak flooring 2.5" wide and also some 3/4" Baltic birch plywood.

I was thinking of using the plywood as a tread base and flooring it with the oak.

Anyone have any recommendations – creative ideas as to what I could do for the nose of the stair tread?

[David Helm]

With many years of experience building and rebuilding stairs, in my opinion the first thing you want to do is add that third stringer. You can then use 5/4 material in just about any wood and the stairs will be stiff.

[Sean Rainaldi]

Thanks David.

By the way, is a 1/4" roundover enough for the stair nosing?

[Steve Bracken]

Thanks David.

By the way, is a 1/4" roundover enough for the stair nosing?

Usually they seem to have a fully rounded nose .... so a bit that is half the tread thickness would be needed.

If you go with the thrrd stringer and 7/8th inch treads, that would be a 1/2" roundover.

Using the smaller one would work in that it would reduce tripping and protect the edge, but it would look a bit different to those I usually see.

[Sean Rainaldi]

Thanks much Steve.

By the way that brings me to another question. I have read in the Michigan building codes two different max riser heights: 7 3/4 and 8 1/4.

Which is correct for residential interiors?

[Lloyd McKinlay]

Depending if you live in an area which has adopted this code.
http://www.arcways.com/pdfs/IRC2006.pdf

[Sean Rainaldi]

I live in Michigan...

[Steve Bracken]

I live in Michigan...

That might not matter.

There are national standards in most fields ... electrics, plumbing, building codes, and many states and localities have adopted them.

All that matters is whether or not your jurisdiction has.

A quick phone call to your local building inspector will reveal exactly which codes they are using, and which they will accept.

Generally, those guys want to help, and appreciate being asked for advice.

[Sean Rainaldi]

Thanks Steve,

One thing I am sure of, when I asked our local inspector months ago, he said our town just uses the current Michigan building codes verbatim so what ever the statewide building codes are for Michigan that's what I need to follow...

[Richard Wolf]

The thickness of your tread material really depends on if you are using risers between each tread. If you are using risers you can use 3/4" white oak and you will not need a third stringer. I would laminate the front 1 1/4" to look like a full thickness treads, which by the way is 1 1/32". Round the front over with a 1/2" round over bit. You will need to use a fence on your router table or your second side will be over cut.

If your stairs are open, no risers, which do not meet code, you will need to use at least 6/4" stock or add a third stringer.

Here is the deal on riser height, at least the way most inspectors look at it. The riser must be below 8" with a margin of error not to exceed 3/8". So in theory, your riser can not exceed 8 5/16". With a minimum run of 9", that make for a pretty steep staircase, close to 43*. Any thing over 41* starts to feel uncomfortable.

[Sean Rainaldi]

Thanks Richard,

I just checked out the 2003 Michigan code again, they call for a max riser height of 8 1/4" and a minimum tread of 9".

Interesting that Michigan exceeds the run by a 1/2" compared to the international code which is 7 3/4" and a 10 inch tread.

Anyone know if 2003 is the most current Michigan residential building code?