Paul,
I have never heard of being allowed to add a non-compliant stair above and existing non-compliant stair. It's just my opinion, but I doubt your jurisdiction would allow it.
I don't know anything about your proposed floor plan. But, it seems a pretty easy thing to add a wider stair above a narrower stair. The framing of the stair hole width above does not need to coincide with the stair hole width below. You just have to correctly carry the loads of the headers at each end.
Additionally, if you raise your starting landing and make it the first riser, or if you turn the last riser at the top, you might gain just enough room for the compliant length of the stair run. That would also help with the headroom of the lower stair. I say this without knowing your floor plan.
Best of luck to you.
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Robert Braddock AIA
Principal
Red House Architects, PLLC
Arlington VA
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Original Message:
Sent: 08-19-2020 20:27
From: Paul Levine
Subject: Single Family Residence Addition
I am working with a client who wants to add a 3rd floor to their existing 2 story single family home. The new 3rd floor will be a bedroom and bath. I have a question regarding the stairs. The existing stair, from the first floor to the second floor, does not meet the 2015 IRBC requirements for the stair width (less than 36") and the tread depth (less than 10"). Because the new stair, from the 2nd floor to the 3rd floor, needs to be above the lower stair, the new stair can not meet the the code requirements without compromising the headroom on the stair below.
My question is, has anybody had to deal with this situation and how was it handled? Is there an exception in the code that allows the new stair to be equivalent to the existing stair? If the new stair were to meet code then the exit path would be constricted once to get to the existing stair. My jurisdiction will not provide a code consultation unless we apply for a permit and the Clients don't want to proceed with construction drawings if it will be denied. Appreciate your expertise.
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Paul Levine AIA
Paul J. Levine, Architect
Pittsburgh PA
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