Rise/run ratio for straight staircase

[scobiewan]

Hi all,

A little background:

We're redoing the stairs in our 1865 house. They were replaced in the 1920s or so and we're trying to put them back more to their original configuration. There are some walnut stair parts from the original stairs in the attic and we plan on reusing as much of them as possible.

We had an architect involved with some other aspects of our renovation, and she also designed the new stair layout for us.

The total rise between floors is 128". She designed a staircase with 17 risers for a unit rise of 7.53". She also specified a unit run of 11".

As I undersand it, this may or may not be code, but definitely violates a couple of the guide formulas that are commonly used (i.e. 2*rise + run = 24"-25").

I'm also reading that the rise should really be kept at or below 7" and that you should only violate that if you have space constraints or something.

So I was thinking of adding an extra stair (unit rise would be 7.11") and making the unit run 10.5" (with +1" bullnose). This would fall within the formula.

One other thing is that it's a straight stair. Is 18 steps too long to go up without a landing somewhere?

Does anyone have any experience with these issues that might have some insight for us? We want the stairs not to feel too steep. But we really want them to feel as comfortable as possible.

Thank you very much in advance! Dan

[Wayne Whitney]

Hello,

I don't really know anything about this, but I can tell you what the

1997 UBC and 2003 IRC say. :-)

Max riser height is 7.75" for IRC, 8" for UBC. Minimum tread depth is

10" for IRC, 9" for UBC. The IRC also requires a nosing between 3/4" and 1 1/4" on stairs with solid risers.

My architect told me that "7.5 inch riser height and 10 inch tread depth is ideal". This may be a matter of personal preference. You might try out various stairs you encounter and measure their riser height and tread depth (ignoring nosing).

Both IRC and UBC require a maximum of 12 feet between landings. So a landing is not required. Personally, I don't think one would be beneficial.

Cheers, Wayne

[DanG]

Many current codes frown on risers over 7". IIRC current IBC is 7

3/8". I try to come as close to 7 rise / 11 tread as possible. This makes a combined riser+tread dimension of 18 or a 2R+tread of

1. There is no limitation of number of continuous stairs of which I am aware. The number is most often determined by dimensions and head clearance issues. The bigger issue, in my professional opinion, is keeping stair noses in plane and avoiding odd gaited risers. IBC speaks to this and limits variations in any run of stairs to 1/4" or so. As has been mentioned here before, a slight variation at top or bottom is not as accident causing as anything mid run.

PRO:The lower the rise, the easier the climb. CON: More steps, more total run distance.

(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]

[Mike]

Check with the local inspector about what local codes you might need to meet. Here, code is not over 8" rise and 10" run and rises must be consistent within + or - 1/8". I think 7.53 would not be too steep (if it's legal) but closer to 7 would be more comfortable. As far as the run goes, you stated 11" run but I wonder if she meant

10" run with an 11" tread. If the jacks are cut for an 11" run you will need a 12" tread to get a 1" overhang. That pretty much eliminates the use of a 2x12 (11 1/4") or pre manufactured treads which I believe are 11".

Mike O.

[bole2cant]

Dan,

Here is my stair program in VB5. The second zip file down:

with different numbers and see what is legal or not.

-Doug

=============================

[Jim Behning]

My house has 6 3/8 rise and 9 inch run. The treads are 10.5 inches. this is a comfortable stair for me. Much less steep than the stairs I grew up on. That house was built about 1900.

Take your tape measure and walk some new houses. I vaguely remember

7/11 as a ratio but that may have been commercial work. http://db.>Dan,

[scobiewan]

Hi Guys,

Thank you all very much for taking the time to comment on my posting. I'm now convinced that we should go with something closer to 7" unit rise. There's no reason not to as we have the space to accomodate the longer opening.

Thanks also for commenting on the need for a landing. I really didn't want to add one and now I don't think we will.

Wayne: Thanks for the modern codes. My books were written in the early 90s and I think they're a little out of date. Do you know why there is a nosing requirement? Also, thanks for the opinion on the landing.

Dan: I read about inspectors not liking anything over 7" even if it was allowed by code. I will also make extra sure the builder keeps the rise constant. I have tripped myself on stairs that were uneven.

Mike: I'll call the city inspector to find out what the local rules are. They were definitely 12" treads. I'm not suprised that she spec'd something non-standard...

Doug: I will download it - thanks!

Jim: Thanks for the tape measure idea. It's a good way to see what feels good under your feet.

Netiquette question: In the future, should I reply to each post individually or is it best to consolidate a reply in a single post like I did here?

Thanks again! Dan

[Larry Jaques]

On 21 Mar 2005 14:58:46 -0800, the inscrutable "scobiewan" spake:

I appreciate the consolidation for two reasons. There are fewer messages to wade through, and all the answers are brought into one message. (My $0.05, adjusted for Iraqui inflation)