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Exceptions to 36" wide stairs in single family homes?

T

travelmodel

Registered User
Joined
Nov 13, 2023
Messages
10
Location
Utah
Hi everyone,

I am remodeling my home to create an accessory dwelling unit (ADU) in my basement. Half of the basement will be for the new unit and the other half stays with the primary home. The new unit will have a 36" door to the outside, and I plan to modify the internal staircase leading to the basement with a "J-hook" (see picture), so that the new apartment will not have access to the internal stairs.

The remodel will work much better if the new stairs can be narrowed to 30" or 32" instead of 36" and I am wondering why the IBC requires 36"? Egress for people seems fine to me at 30", so I assume the reason is more about moving furniture? If so, the new internal wall that separates the ADU from the primary home will have a 36" locked door which will allow furniture movement so that the internal stairs will ONLY be used for people. (It can also be unlocked easily from the primary side to allow for emergency exit).

Are you aware of exceptions for single family homes for cases like this, where there are two paths or staircases, and one of them is 36" (thus making it possible for the other to be smaller, say 30 or 32"?)
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travelmodel said:
Egress for people seems fine to me at 30", so I assume the reason is more about moving furniture?
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It has more to do with carrying a laundry basket. Is the laundry equipment in the basement? :cool:
Good job with the visuals and welcome to the forum.

R311.7.1 Width. Stairways shall be not less than 36 inches in clear width at all points above the permitted handrail height and below the required headroom height. The clear width of stairways at and below the handrail height, including treads and landings, shall be not less than 311/2 inches where a handrail is installed on one side and 27 inches where hand-rails are installed on both sides.

Be aware that this is California code and yours might be different.
 
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I believe the 36" requirement came into the CABO code (forerunner of the IRC) in the 70s or 80s largely due to pressure from movers. A 30" dogleg stair will make moving furniture or laundry baskets very difficult.

It might be possible to obtain a code modification if you can show that there is a second 36" stair, or a 36" door on the main level as well as basement. You should discuss this with your local building official before going too far with the drawings.
 
travelmodel said:
Hi everyone,

I am remodeling my home to create an accessory dwelling unit (ADU) in my basement. Half of the basement will be for the new unit and the other half stays with the primary home. The new unit will have a 36" door to the outside, and I plan to modify the internal staircase leading to the basement with a "J-hook" (see picture), so that the new apartment will not have access to the internal stairs.

The remodel will work much better if the new stairs can be narrowed to 30" or 32" instead of 36" and I am wondering why the IBC requires 36"? Egress for people seems fine to me at 30", so I assume the reason is more about moving furniture? If so, the new internal wall that separates the ADU from the primary home will have a 36" locked door which will allow furniture movement so that the internal stairs will ONLY be used for people. (It can also be unlocked easily from the primary side to allow for emergency exit).

Are you aware of exceptions for single family homes for cases like this, where there are two paths or staircases, and one of them is 36" (thus making it possible for the other to be smaller, say 30 or 32"?)
View attachment 11986
Click to expand...
Are you supposed to be in the IBC or IRC?
 
ICE said:
It has more to do with carrying a laundry basket. Is the laundry equipment in the basement? :cool:
Good job with the visuals and welcome to the forum.

R311.7.1 Width. Stairways shall be not less than 36 inches in clear width at all points above the permitted handrail height and below the required headroom height. The clear width of stairways at and below the handrail height, including treads and landings, shall be not less than 311/2 inches where a handrail is installed on one side and 27 inches where hand-rails are installed on both sides.

Be aware that this is California code and yours might be different.
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There will be two laundry rooms: one in the basement for the ADU and the other upstairs for the primary residence.
 
Paul Sweet said:
I believe the 36" requirement came into the CABO code (forerunner of the IRC) in the 70s or 80s largely due to pressure from movers. A 30" dogleg stair will make moving furniture or laundry baskets very difficult.

It might be possible to obtain a code modification if you can show that there is a second 36" stair, or a 36" door on the main level as well as basement. You should discuss this with your local building official before going too far with the drawings.
Click to expand...
This was a very helpful comment explaining that the 36" requirement isn't really about safety - it's about moving "big stuff," (furniture and laundry). I'm trying to reach our building officials to see if they have a variance process since I can show how big stuff will be able to move throughout the house without using these stairs. Thank you!
 
steveray said:
Are you supposed to be in the IBC or IRC?
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I don't know. I'm trying to reach them but they haven't responded yet. But thanks for this tip because I can ask them. Are the requirements different? Does one allow for exceptions like mine, while the other doesn't? Is there a way to reach the authors of these codes and suggest they include this type of case in a future code update?
 
travelmodel said:
the 36" requirement isn't really about safety - it's about moving "big stuff
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You have been misled. Building code is all about safety. Of course there are usefulness considerations inadvertently built in the code. For example, many people think that second floor balconies are for enjoying traffic when in fact a balcony and it's sliding door is for bringing in the armoire.

A condo that I owned wouldn't have a refrigerator if there wasn't a balcony. Oh and the couch took six people to wrestle it in....and out.
 
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travelmodel said:
I don't know. I'm trying to reach them but they haven't responded yet. But thanks for this tip because I can ask them. Are the requirements different? Does one allow for exceptions like mine, while the other doesn't? Is there a way to reach the authors of these codes and suggest they include this type of case in a future code update?
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Welcome to the forum. I see you are located in Utah - - is that where the project is also located?
 
The reason why is immaterial, the code requires a 36 inch stair width, above the handrail. Build a compliant stair or ask for a variance.

if the stair is not a means of egress look at using a alternating tread device or ships ladder.
 
It seems all would be code compliant without those stairs. I think I'd focus on that in asking for a variance. Even a narrow stair is safer than ladders, ships ladders, alternating tread devices (horrible in my experience), or similar.
 
Don't just think of people going up the stairs, think of firefighters in full kit, EMTs carrying a stretcher out, etc... Larger individuals on a stretcher would present a major problem.

I would not go below 36". Squeeze the kitchen if you must, go to 24" appliances in the laundry, eliminate closets and use the space, but do not try to squeeze the means of egress. It is absolutely about safety.
 
The 36" is not for moving, "STUFF"
It is about life safety.
As stated by Beniah above, it is about ".....firefighters in full kit, EMTs carrying a stretcher..."
It is about life safety.

No exceptions to the minimum.
 
I have seen secondary stairways in older homes with less than 36" width, usually in the back of the house, they have been called "butler" or "servant stairways" in the past, they probably have to be reclassified. We call them existing-nonconforming or Grandfathered stairways.

In your case, just non-conforming, not to code, FD or EMT still has to get to the party below!
 
SCBO1 said:
I have seen secondary stairways in older homes with less than 36" width, usually in the back of the house, they have been called "butler" or "servant stairways" in the past, they probably have to be reclassified. We call them existing-nonconforming or Grandfathered stairways.

In your case, just non-conforming, not to code, FD or EMT still has to get to the party below!
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Even though there is a fully compliant m.o.e. direct to exterior?
 
Bill,

My post, the houses still have their main front stairways that are compliant. A firefighter or EMT still may have to go up or down the stairs to the party in need?

I was thinking that the basement access was smaller in width, did I miss something?
 
travelmodel said:
The remodel will work much better if the new stairs can be narrowed to 30" or 32" instead of 36" and I am wondering why the IBC requires 36"? Egress for people seems fine to me at 30", so I assume the reason is more about moving furniture? If so, the new internal wall that separates the ADU from the primary home will have a 36" locked door which will allow furniture movement so that the internal stairs will ONLY be used for people. (It can also be unlocked easily from the primary side to allow for emergency exit).

Are you aware of exceptions for single family homes for cases like this, where there are two paths or staircases, and one of them is 36" (thus making it possible for the other to be smaller, say 30 or 32"?)
Click to expand...
Based on IRC R311.7 (I assume this falls under Residential Code), all stairs, required OR provided (meaning literally any proposed stairs regardless if they're required by code or not), unless they meet one of the exceptions listed in that section, MUST be 36" wide. This is for life safety, not furniture. As other's have pointed out, the last thing you want is to be stuck in an emergency and have paramedics or fire fighters unable to reach you because the stairs are too narrow. Even ignoring emergency personal, having a wider staircase is practical for emergency egress.

Just in case this project doesn't need to conform to Residential code for any reason, then IBC 1011.2 forces the stairs to be 36".
 
SCBO1 said:
Bill,

My post, the houses still have their main front stairways that are compliant. A firefighter or EMT still may have to go up or down the stairs to the party in need?

I was thinking that the basement access was smaller in width, did I miss something?
Click to expand...
My understanding is if these stairs were omitted, all parts of the building would still have all the required m.o.e.

arwat23 points out that even non-required stairs and I presume other m.o.e. components are required to comply. While I have pointed out that the m.o.e. from the middle of a stair is that stair, somehow in a one or two family dwelling it feels like code overreach.
 
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