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Rise/run ratio for straight staircase



 
 
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  #1  
Old March 20th 05, 05:48 PM
scobiewan
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Default Rise/run ratio for straight staircase

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

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  #2  
Old March 20th 05, 06:08 PM
Wayne Whitney
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Default

Hello,

I don't really know anything about this, but I can tell you what the
1997 UBC and 2003 IRC say. :-)

On 2005-03-20, scobiewan wrote:

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".


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).

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


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
  #3  
Old March 20th 05, 06:12 PM
DanG
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Default

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
25. 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)




"scobiewan" wrote in message
oups.com...
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



  #4  
Old March 21st 05, 12:00 AM
Mike
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Posts: n/a
Default

On 20 Mar 2005 09:48:34 -0800, "scobiewan"
wrote:

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".


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.
  #5  
Old March 21st 05, 04:48 AM
bole2cant
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Default

Dan,

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

http://www.xmission.com/~sherwin/download1.htm

Play with different numbers and see what is legal or not.

-Doug

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

"scobiewan" wrote in message
oups.com...
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



  #6  
Old March 21st 05, 01:09 PM
Jim Behning
external usenet poster
 
Posts: n/a
Default

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.inman.com/inman/content/su...nistid=Gellner
http://www.popularmechanics.com/home...c/1275341.html

My stairs are fine going up. Coming down they seem a little steep. I
have seen worse. Well both those areticle suggest rise+run=17-18" Mine
misses that by 1.5" which would explain why it feels a bit steep going
down. I have been in houses with about 8 by 8. Those really feel
steep.

"bole2cant" wrote:

Dan,

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

http://www.xmission.com/~sherwin/download1.htm

Play with different numbers and see what is legal or not.

-Doug

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

"scobiewan" wrote in message
roups.com...
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



  #7  
Old March 21st 05, 10:58 PM
scobiewan
external usenet poster
 
Posts: n/a
Default

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

  #8  
Old March 22nd 05, 01:59 PM
Larry Jaques
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Posts: n/a
Default

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

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?


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)


--

People will occasionally stumble over the truth, but
most of the time they'll pick themselves up and carry on.
--anon
 




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