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Old 03-15-2013, 02:21 PM   #1
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Best way to adjust riser hight and stay withing code


I am installing retro treads to replace the carpeting on my existing stairway. I will also be adding 3/4" bull nosing on the landing to accomodate carpeting on the landing. The retro-treads are 3/4" thick, the standard rise height is 7 4/8" (with the exception of the the 1st step which is only 7 2/8 due to a new floor install). The addition of the landing nosing increases the top to bottom height of the stairs from 74 6/8" to 75 4/8". This means that I have to adjust the riser height on one or more of the steps at the bottom to accomodate this increase. To do this, I would tear out an existing tread and replace it with a thinner (adjusted) tread. The retro-treads would then be installed on the thinner (adjusted) treads.

In short, I have options to spread the adjustment out over one or more steps. The below table shows what the new riser heights would be depending on any adjustments to the height of some of the existing old treads.

Option 1: Install the new retro-treads and nosing without any change to the old tread height.

Option 2: Replace the tread on the 1st step with a tread that is 2/8" thinner.

Option 3: Replace the treads on the 1st and 2nd steps with a tread that are 2/8" and 1/8" thinner repectively.

Option 4: Replace the treads on the the 1st, 2nd, and 3rd step by treads that are 3/8", 2/8" and 1/8" thinner repectively.

In short, spreading out the adjustment over more steps reduces the variance of any one step from the 7 4/8" standard rise, but it is also means that more steps will have a variance from the standard 7 4/8" rise. It also involves tearing out and replacing more old treads. What option below do you think is best choice in order to stay within code while also minimizing the number of old treads to tear out and replace. The code I want to comply with states: "The rise and run of steps shall be uniform in size, shape and the variation cannot exceed 3/8 inch in the total run."

,
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Last edited by hkeiner; 03-16-2013 at 03:56 PM.
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Old 03-15-2013, 07:05 PM   #2
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Best way to adjust riser hight and stay withing code


I am a tad bit confused. If you are adding 3/4" thick retro treads to the existing treads the landing will also be 3/4" higher (if you use a retro for that tread as well. If that is true you could run your carpet up to the back side of the landing retro tread and then install a thin jointing strip over the seam.

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Old 03-15-2013, 07:14 PM   #3
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Best way to adjust riser hight and stay withing code


Option 4 is the closest to code that usually says no more than 1/8" variation between largest and smallest riser.
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Old 03-15-2013, 07:37 PM   #4
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Best way to adjust riser hight and stay withing code


Quote:
I am a tad bit confused. If you are adding 3/4" thick retro treads to the existing treads the landing will also be 3/4" higher (if you use a retro for that tread as well. If that is true you could run your carpet up to the back side of the landing retro tread and then install a thin jointing strip over the seam.
The risers for the upper steps all stay at 7 1/2", so they are OK. The problem I have is with the 1st step, where there is a 1/2" of extra rise to handle (adding the 3/4" retro-tread less the 1/4" that the 1st step rise was shorter than the rest of the steps because of the higher floor at the bottom).

Thanks for your interest in my problem.
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Old 03-15-2013, 08:02 PM   #5
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Best way to adjust riser hight and stay withing code


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Option 4 is the closest to code that usually says no more than 1/8" variation between largest and smallest riser.
I googled the internet to see what the code for stairway riser height is and found that the exact text varies a bit, but they all seem to use "3/8" as part of the code text, similar to what I quoted in my first post. I show below a few other examples of code text for comparison.

Does the "1/8" variation you mention apply to a different section of code or is it a more stringent interpretation of the code I mention? I don't want to be too granular, but I figure I should confirm whether options 2 or 3 are within code before eliminating them as a choice. I can definately see that option #1 is not compliant with code by any interprepation and that option 4 results in the the closest to perfect stair risers.



--------------------------------
The Codes (2009 IRC):
  • 311.7.4.1 – Maximum Riser Height is 7 ” (max. height difference of 3/8” based on all risers)
-------------------------------
1009.3 Stair Treads and Risers.

Stair riser heights shall be 7 inches maximum and 4 inches minimum. Stair tread depths shall be 11 inches minimum. The riser height shall be measured vertically between the leading edges of adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 0.375 inch.

---------------------------
Sections from 2010 California Residential Code Section R311 Means of Egress & Section R112 Guards

R311.7.4.1 Riser Height. The maximum riser height shall be 7 3/4 inches. The riser shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch.

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Old 03-15-2013, 11:39 PM   #6
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Best way to adjust riser hight and stay withing code


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Originally Posted by hkeiner View Post
Sections from 2010 California Residential Code Section R311 Means of Egress & Section R112 Guards

R311.7.4.1 Riser Height. The maximum riser height shall be 7 3/4 inches. The riser shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch.
the Cali code is based upon the IRC as most local building codes do. If you are located in Cali then the 3/8" applies to your situation.

Some local jurisdictions have modified the IRC requirement, i.e., in Massachusetts our maximum riser height is 8-1/4", but again the 3/8" applies here
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Old 03-16-2013, 08:28 AM   #7
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Best way to adjust riser hight and stay withing code


Regardless of what the code says, the most important thing with stairs is to have them all the same. Even a 1/4 inch can cause someone to take a nose dive. Its amazing how the brain is such an incredible computer.
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Old 03-16-2013, 11:58 AM   #8
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Best way to adjust riser hight and stay withing code


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Regardless of what the code says, the most important thing with stairs is to have them all the same. Even a 1/4 inch can cause someone to take a nose dive.
Very good point. I think I'll do option #4 and spread the variance evenly among the bottom 4 steps. A bit more work this way, but a more 'professional' job I think.

Thanks to everyone for their input.
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Old 03-16-2013, 09:20 PM   #9
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Best way to adjust riser hight and stay withing code


I'd definitely go with option 4, it's your best option. Btw, reduce those fractions!
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Old 03-16-2013, 10:12 PM   #10
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Best way to adjust riser hight and stay withing code


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reduce those fractions!
math teachers around the world are smiling ...
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Old 03-17-2013, 02:41 AM   #11
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Best way to adjust riser hight and stay withing code


I used a common denominator to make the comparisons easier.
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Old 03-17-2013, 11:57 AM   #12
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Code or not, 1/8" maximum variation is the industry standard that has been taught for hundreds of years. If you took a 1/2" board and stuck it on any stair tread in the middle of the run most people trip on it on the way up, land harder stepping on it, and then feel a drop after it on the way down. You would only get away with more before the second step.

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