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R2, single stair, 3-story: roof deck & penthouse questions

Sasquatch

Sasquatch

Registered User
Joined
Apr 20, 2018
Messages
9
Location
Bothell, WA
Hi all,

Long time lurker, first time poster. I'm an architect near Seattle currently permitting a project I'm designing and developing for myself/family. The building is about 30'x60', on a corner of two city streets. It's 3 stories, type VB, and utilizes the single stair exception. The top floor plate is 33' from grade. The stair is exterior and will have 1-hour fire protection where it adjoins units since I have no room for the 10' fire separation. This stair is 1' from the property line on the side of the public sidewalk and street R.O.W. The ground floor has a small B occupancy commercial space (576 SF) and an S2 carport. The upper two floors are all R2. The second floor is two apartments, (725 SF & 810 SF), and the third floor is one apartment at 1586 SF. The roof is intended to be a private roof deck for the upper apartment only, with access only through the upper apartment itself, not accessible to the other tenants. The ground floor is sprinkled with NFPA 13, while the upper two R2 stories are sprinkled with 13R.

I have a few confusing (to me) questions about how to interpret the 2015 IBC given the above:

1. Since putting anything horizontal on the roof deck would make it a 4th floor, that must be avoided, but are we allowed to have a penthouse just big enough to roof over the stair to the roof from the 3rd floor R2 dwelling? IBC 1510.2.3 says "vertical shaft opening" but ours would be open air with a roof over the stair; probably just a single wall or two supporting a roof over the stairs. The stair to the roof is a continuation of the common stair below but walled off from tenants so you have to go through the upper apartment to get roof access.

2. If I don't want to or can't build the penthouse mentioned above, can I install a large access hatch that sticks up no more than 48" from the roof deck surface?
(I know the code has evolved a lot on roof decks in the 2015 IBC, so it's all very vague to me).

3. My common path of egress travel from the furthest point in the 3rd floor unit to the exit door at the bottom of the exterior stair (where two paths can be taken), is just under 125 LF allowed for a single stair building. If I have to measure the exit path from the roof deck I won't make it within 125 LF. Do you know if I have to count the roof deck exit distance since it's not officially a "story" in the IBC? I have no idea. Same question would go for counting the distance from the edge of an exterior balcony to the exit door at grade. If I do then I will have to scrap the roof deck (except for maintenance access?), or find a way to add a second egress stair (maybe impossible). It seems like this is NOT an occupied roof because it's not a story, but I don't really know if that term applies either.

I probably have some other questions, but those are the most pressing right now, if anyone has insight. Thanks in advance if you can help.
 
Sasquatch,
Welcome to the BCF!
Assuming Seattle adopted the 2015 IBC without amendments Section 1006.3.2 require that the travel distance be measured from the occupiable roof though it's not a story.
The hatch is permitted "in buildings without an occupied roof (1011.12.2). The same for a penthouse (see def.).

A continuous exit stair to the roof is an option as staircases are restricted to building height in Chapter 5.
Depending on the AHJ what we allow is the enclosed landing floor area to be less than 70 sf. to not qualify as habitable space. Note code provides the minimum landing size but it doesn't limit the maximum.
We also limit the roof overhang or projection since it also contributes to the building and fire area for the story.

Sure to have more feedback on Monday.
 
Francis,
Thanks so much for the quick response. I think that the fact that I can't get the travel distance from the roof under 125' might sink the whole plan of using the roof deck, which is a damn shame. I planned the building to have this fabulous roof deck that we looked forward to enjoying.

And so if I understand you clearly, for the hatch or penthouse, they're acceptable for roof access, but not if we want to occupy and use the roof. So it's a catch-22 I guess. I can build them to get up there, but I'm not allowed to use the roof deck for relaxing. How do they make the distinction? Is it whether you install guardrails or not, for example?

Right now we do have a continuous stair to the roof that all units could use to access the roof, but I thought I had to change it to a private stair for the section to the roof (from 3rd floor unit only). Are you saying that there's a way for us to have a common stair to the roof for all tenants? We are under the allowed building height by a lot. I thought that might make it an assembly space on the roof, in which case we'd have to keep it below 49 occupants. Or are you saying the common stair can go to the roof and then the enclosed (penthouse?) landing at the top can't be over 70 SF?

So I guess I just have more questions. You can see why I've written into this forum! Thank you.
 
Is it possible to set up permanent barriers (guards) to reduce the travel distance?

For a shared roof may review with the AHJ of an open roof top garden that could restrict access.

Most of my roofs have 2 exits or meet the travel distance with barriers.
 
I did the calcs and we could easily have a roof space up there and restrict access with tall planters or other barriers. I just wasn't sure if I could even have a roof area that can be used or accessed by all 3 apartments on a roof over the 3rd floor. I can't find what code clause allows that, or disallows!
 
Sasquatch said:
I did the calcs and we could easily have a roof space up there and restrict access with tall planters or other barriers. I just wasn't sure if I could even have a roof area that can be used or accessed by all 3 apartments on a roof over the 3rd floor. I can't find what code clause allows that, or disallows!
Click to expand...
As a kind reminder depending on the AHJ; Section 1004.5 "The occupant load of such outdoor areas shall be assigned by the building official in accordance with the anticipated use. " Also see exception 2.
 
To further clarify my reply in post 2., the occupiable roof access by observation will appear to be a penthouse but wouldn't be identified as such owing to its application.

On the plans it would be identified as a roof exit access stairway, an interior exit stairway or a stair tower as appropriate.
 
Last edited:
Francis, again thanks for all the advice, it’s really helpful. The fact it comes down to negotiating with the AHJ tells me a lot about how the code doesn’t have a pat answer for this. I’m leaning towards just making it a non-occupiable roof deck with a ship’s ladder and roof hatch to access and maintain the HVAC equipment and a few solar panels. The access is required in the IMC anyway. I’d rather get it through permit for now, then maybe negotiate a roof stair exit later for a remodel as its own project after the building is up.
 
Would upgrading to a full 13 sprinkler system make a difference? (not looking at the code right now, so just thinking out loud)
 
Not sure if it helps, but I think it is on height that the code uses the average of the roof line.

Say one side is 30 ft and the other half is 40 ft, you would have a 20 ft average ht? not sure if that helps with story.


"""" 1. Since putting anything horizontal on the roof deck would make it a 4th floor"""" read the definition of story.
 
cda said:
"""" 1. Since putting anything horizontal on the roof deck would make it a 4th floor"""" read the definition of story.
Click to expand...
cda, where stairwells have intermediate landings (floor levels that do not qualify as mezzanines) and serve a "three" story building and the roof is actually a seven story structure?
 
As it stands, I'm removing roof deck access completely right now and just providing a roof hatch and ship's ladder for required access to the HVAC and other equipment on the roof. Without a clearer understanding of whether I can even use the roof for "enjoyment" with the single stair, it seems like being conservative is the best way to get this through permit, then maybe I have a conversation with the AHJ before framing to see if I can negotiation any private access for the top floor R2 apartment, which may be the best I can do. I remain open to ideas and solid code interpretations on the matter. I'm surprised this isn't more clear in the code, given how popular roof decks are these days.
 
Looks like you already have your answer but I will throw in my local amendment which requires that an occupied roof area must provide the same exiting requirements that would normally be provided for a story. We have a number of roof decks and folks often fight against the idea of having a second stairway. We started to draft our own interpretation and then decided to steal a page from Omaha. The amendment below applies to multi-family and all other commercial projects:

Section 1509.9 Added; Outdoor Deck Framing for Roof Top Seating and Assembly Areas.

Section 1509.9 is added to the International Building Code to read as follows:

1509.9 Outdoor deck framing for roof top seating and assembly areas. Combustible wood framing may be permitted on roof tops of buildings provided that the roof is not located more than 75 feet above the lowest level of fire department vehicle access. In addition to this limitation, the combustible framing may not exceed four feet in height above the floor or deck level used as a walking surface. Similar structures that exceed 48 inches in height shall be of a type of construction not less in fire-resistance rating than required for the building to which it is attached. Occupied roofs shall be provided with exits as required for stories, regardless of whether roof top construction is enclosed or open to the sky. Any such structure that is covered shall be provided with all fire protection systems required for the building to which it is attached. All such structures intended for human occupancy shall have minimum 42-inch high guard rails regardless of their height above the plane of the roof. Floor deck area shall be limited to one-third total roof area.
 
Sasquatch said:
As it stands, I'm removing roof deck access completely right now and just providing a roof hatch and ship's ladder for required access to the HVAC and other equipment on the roof. Without a clearer understanding of whether I can even use the roof for "enjoyment" with the single stair, it seems like being conservative is the best way to get this through permit, then maybe I have a conversation with the AHJ before framing to see if I can negotiation any private access for the top floor R2 apartment, which may be the best I can do. I remain open to ideas and solid code interpretations on the matter. I'm surprised this isn't more clear in the code, given how popular roof decks are these days.
Click to expand...


Build it only so big, Sq ft

That you only need one exit
 
cda said:
Build it only so big, Sq ft

That you only need one exit
Click to expand...
I can definitely do that. That's actually the easy part, since I can go about 30' away from the edge of the stair at the roof and still stay within 125' of the exit discharge at ground level. If it's R2 occupancy then my whole roof would still only have an occupancy of 7! If it was Assembly, then I could easily keep it below 49 occupants. However, I'm concerned that I can't do Assembly occupancy at all or it will be an occupied roof and the second exit would be required. I wouldn't even mind building a second stairway if I had the space on my tiny urban lot, but I don't.
 
The roof is intended to be a private roof deck for the upper apartment only, with access only through the upper apartment itself, no


This might help you

You can always design it in and see if it flys past ahj!!

If not just hit the delte button
 
cda said:
The roof is intended to be a private roof deck for the upper apartment only, with access only through the upper apartment itself, no


This might help you

You can always design it in and see if it flys past ahj!!

If not just hit the delte button
Click to expand...

Yeah, I'm just deleting it for now to get it approved. Then I can run the idea of a private roof deck for the upper apartment by the AHJ after I'm into groundwork. I'd rather stay on schedule right now that fight with reviewer over the roof deck.
 
The occupiable roof above the 3rd story is not permitted with a single exit as it would be considered a 4th story in accordance with Section 1006.3.2 items 1. & 5. provided below. Let me know if the images cannot be viewed.

However one could request a modification that the travel distance would be comparable from a mezzanine in the 3rd story.

Table.PNG

1. The occupant load, number of dwelling units and exit access travel distance do not exceed the values in Table 1006.3.2(1) or 1006.3.2(2).

5. Individual single-story or multistory dwelling units shall be permitted to have a single exit or access to a
single exit from the dwelling unit provided that both of the following criteria are met:
5.1. The dwelling unit complies with Section 1006.2.1 as a space with one means of egress.
5.2. Either the exit from the dwelling unit discharges directly to the exterior at the level of exit discharge, or the exit access outside the dwelling unit’s entrance door provides access to not less than two approved independent exits.
Multi.PNG
 
Francis Vineyard said:
The occupiable roof above the 3rd story is not permitted with a single exit as it would be considered a 4th story in accordance with Section 1006.3.2 items 1. & 5. provided below. Let me know if the images cannot be viewed.

However one could request a modification that the travel distance would be comparable from a mezzanine in the 3rd story.

View attachment 2845

1. The occupant load, number of dwelling units and exit access travel distance do not exceed the values in Table 1006.3.2(1) or 1006.3.2(2).

5. Individual single-story or multistory dwelling units shall be permitted to have a single exit or access to a
single exit from the dwelling unit provided that both of the following criteria are met:
5.1. The dwelling unit complies with Section 1006.2.1 as a space with one means of egress.
5.2. Either the exit from the dwelling unit discharges directly to the exterior at the level of exit discharge, or the exit access outside the dwelling unit’s entrance door provides access to not less than two approved independent exits.
View attachment 2846
Click to expand...
This is great. In fact, this is what I had sketched out a couple months ago in case this issue came up, i.e. I would essentially create an upper level mezzanine or loft like space for the upper apartment that included a door to a modest outdoor roof deck. This is what I may propose after it's (hopefully) permitted. I'm really glad to see you suggest this, which makes me think the idea might be acceptable.
 
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