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Single Family Residence Addition

  • 1.  Single Family Residence Addition

    Posted 08-19-2020 08:28 PM
    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.

    Paul Levine AIA
    Paul J. Levine, Architect
    Pittsburgh PA

  • 2.  RE: Single Family Residence Addition

    Posted 08-20-2020 05:36 PM
    Would it be possible to make the new stair longer than the existing one?  If there is not enough space between walls, perhaps a winder or square landing at the bottom with another riser or two?

    Bruce Ward AIA
    Bruce Ward Architect
    Hamilton NY

  • 3.  RE: Single Family Residence Addition

    Posted 08-21-2020 06:18 PM
    I think some of these answers have muddied the waters, especially concerning the need for a second stair, which is not a requirement in a single family home.  I'm assuming that there is no stair to the current attic.  I believe you are correct in that any new stair must meet the code for new construction.  Any new stair cannot make the existing means of egress any more non-conforming than they already are.  So if the new stair creates a headroom problem that makes the existing stair more non-conforming it would not be allowed.  My opinion is that the issue of the reduction in egress width would be acceptable because you are making all new areas meet the code.  That does not prevent you from being able to pass through a non-conforming space on your way from the new space.  Unfortunately this is one of any number of scenarios that are not clearly spelled out in the code.

    I assume you do not already have a stair to the attic.  If you do it would not have to be updated if there is any type of legal (i.e. built with a building permit) living space in the  attic already.  In other words, if there is already a finished space up there the existing stair is okay even  if you are adding new construction, such as a shed dormer.  If there is no legal living space up there, even an existing non-conforming stair would have to be updated.

    Although it is within the building inspector's right to wait for the full set of drawings (at least one way of reading IRC R104), he/she is certainly doing you and your customer a disservice.  He/she is the only person who can make such an interpretation.  You have the right to appeal their interpretation, but no matter what you or I think about it, their interpretation is what matters (unless appealed).  I've never had a building inspector refuse such a question when adequate design level drawings that fully illustrate the issue are presented.

    John Crowell
    Deer Hill Architects, LLC
    Peabody MA

  • 4.  RE: Single Family Residence Addition

    Posted 08-20-2020 06:09 PM
    I'm guessing you're dealing with an expansion into an existing attic.   In an old house with an existing stair the official may just accept the existing conditions. The stairs may be the least of the problem.  We usually have issues of the attic floor joist are too small and the rafters aren't big enough install the insulation required to meet the energy code.

    Peter Carlsen AIA
    Carlsen & Frank Architects
    Saint Paul MN

  • 5.  RE: Single Family Residence Addition

    Posted 08-20-2020 06:25 PM
    Hi Paul:

    Take a look at the Existing Building code - 2019 Residential Code - Existing Building Code - Section AJ103 - Page 590 (2016 Code) Preliminary Meeting - (Note - I have condensed the essence of the text) - "If a building permit for the proposed work is required, the building official or his/her designee shall meet with the prospective permit applicant prior to the application for a permit to determine the applicability of the code based on the scope and conditions".  

    This should be an opportunity to discuss your issues and possible solutions that would be acceptable to the building official and do so without having applied for a permit yet. On the one hand it is questionable to ask for forgiveness to not to meet code for new work - however, that should not trigger updating existing conditions unless your scope (>50% of existing) triggers code upgrades.  


    Bill Gregory, AIA


    Arcelab Inc. Architects

    7480 S. Osage Ave.

    Los Angeles, CA 90045

    Cell - 310-507-5434

    Fax - 310-910-0483

    Web Site -

  • 6.  RE: Single Family Residence Addition

    Posted 08-20-2020 07:30 PM
    The shape of the stair (straight? L-shaped? etc) is a factor, as is whether you can borrow a small amount of space on the 2nd floor to get you to a greater width and a higher level before going directly above the existing stair, as is how big an opening you can accept in the 2nd fl. ceiling/3rd fl. floor.

    In MA a new stair connecting inhabited spaces needs to conform to code.

    Leah Greenwald AIA
    Leah Greenwald, Architect
    Waltham MA

  • 7.  RE: Single Family Residence Addition

    Posted 08-20-2020 11:58 PM

    The last time I converted a 3rd floor into a bedroom I had a similar stacking issue. Plus the code required us to add a second stair from third floor.  We ended up designing one stair to align with the existing stairs (too steep and narrow) and the other meeting the rise, run and width of the current code.  


    Katherine S. Georgeson, FAIA, NCARB, LEED AP

    ORCHESTRA Design Studio



  • 8.  RE: Single Family Residence Addition

    Posted 08-21-2020 03:11 PM
    It is my understanding that most municipa;ities that use the International Residential Code (IRC) and IBC have an appeals board.  I have found that is a successful preceedure.

    Richard Frantz, AIA

    P. Frantz AIA
    P. Richard Frantz, AIA, Architect
    Pottstown PA

  • 9.  RE: Single Family Residence Addition

    Posted 08-24-2020 05:39 PM
    Different direction on the stair issue:
    My first and non-negotiable concern is life safety and that should be long term: your practice and for the building in perpetuity. Occasionally a client asks for something that cannot be configured safely. If an "outside the box" solution cannot be found (perhaps an exterior stair, a deep reconfiguration gaining them more), have the backbone to say no, and say why. They should respect you (and the profession) for the candor! Think hard about hearing in years to come of the fire, the loss of life and your ethical responsibility.

    Jonathan Siegel AIA
    Siegel Design Architects, LLC
    Albuquerque NM

  • 10.  RE: Single Family Residence Addition

    Posted 08-21-2020 05:15 PM

    IRC R311.7, exception #2, allows stairs as narrow as 32" if you are converting an existing attic stair to access a newly finished attic.  But you are proposing the installation of a new, too-narrow egress stair, so this provision would not directly apply.  If your proposed stair is only very slightly narrower than the required 36" you might submit a variance request to your state building official, arguing that your stair would be at least as safe as allowed by exception #2 (32" wide).  This would not be an as-of-right situation, so you would be at the mercy of the building official's decision.  You might combine your variance request with other compensating measures, that exceed minimum code requirements, to help make up for your narrow stair.  These might include such items as more and larger egress windows, installation of residential fire sprinkler coverage for the home (or at least for the 3rd floor), installing extra interconnected smoke and heat detectors throughout the dwelling and connecting them to a robust, monitored alarm system.  You might build balconies outside of the third floor windows, and provide egress ladders from those balconies.  None of these extras would "earn" a variance, but may give the official justification for granting a variance, particularly if your proposed stair is only slightly too narrow.


    Your treads slightly less than 10" should not be a problem because 311.7.5.2 allows treads as narrow as 9" as of right.


    Carl Mezoff

    A  r  c  h  i  t  e  c  t,   P.  E.

    1100 Rock Rimmon Road

    Stamford, CT 06903

    203 329 0066


  • 11.  RE: Single Family Residence Addition

    Posted 08-21-2020 11:19 PM

    In 2006 there was the International Existing Building Code, but I don't know if that code is still being produced.  If it is, maybe it can lend some insight.

    -Russ Ver Ploeg, AIA, LEED AP

  • 12.  RE: Single Family Residence Addition

    Posted 08-22-2020 02:22 PM
    Minnesota has adopted the Conservation Code for Existing Building, but I believe it does not apply to buildings governed by the IRC.