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Elevator Shaft Wall Construction Above Roof Slab

fj80

fj80

Sawhorse
Joined
Jan 18, 2016
Messages
230
Location
Virginia
Jurisdiction: Washington, DC. Codes: 2012 ICC Existing Building Code, 2013 DC Building Code (which seems to be the same as IBC 2012 for this topic.)

We're renovating an existing two story building (Type 2B construction) including adding an elevator. The elevator shaft extends about four feet above the existing concrete roof, to allow room for the elevator equipment at the top of the shaft. The hoistway walls are 2-hour rated (because they penetrate a 6" concrete floor slab and per IBC 713.4 the shaft wall rating must match the floor rating up to 2 hours.)

My question is this: Does the hoistway wall assembly need to be the same above the roof as it is below the roof?
Additional information: We're using steel stud framing, and the hoistway walls are within 10' of the side of the building which is also the property line, and the neighboring building is also built up to the property line. I figure this last fact may be important for using Tables 601 and 602.

My inclination is to continue the 2-hour rated shaft wall above the roof, just like it is for the rest of the hoistway below the roof, with the addition of a stucco finish on the exterior.

Any help would be much appreciated.
 
3002.1 Hoistway enclosure protection.
Elevator, dumbwaiter and other hoistway enclosures shall be shaft enclosures complying with Section 713.

713.5 Continuity.
Shaft enclosures shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both, and shall have continuity in accordance with Section 707.5 for fire barriers or Section 711.4 for horizontal assemblies as applicable.


707.5 Continuity.
Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling. Joints and voids at intersections shall comply with Sections 707.8 and 707.9.


713.12 Enclosure at top.
A shaft enclosure that does not extend to the underside of the roof sheathing, deck or slab of the building shall be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.

Since you are penetrating the roof deck/slab IMHO you will need to make the shaft comply with 713.12 through the roof and across the top
 
713.5 Continuity.
Shaft enclosures shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both, and shall have continuity in accordance with Section 707.5 for fire barriers..


So 707.5 states:

707.5 Continuity.
Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling. Joints and voids at intersections shall comply with Sections 707.8 and707.9.

707.5.1 Supporting construction.
The supporting construction for a fire barrier shall be protected to afford the required fire-resistance rating of the fire barrier supported. Hollow vertical spaces within a fire barrier shall be fireblocked in accordance with Section 718.2 at every floor level.

Exceptions:
1. The maximum required fire-resistance rating for assemblies supporting fire barriers separating tank storage as provided for in Section 415.8.2.1 shall be 2 hours, but not less than required by Table 601 for the building construction type.
2. Shaft enclosures shall be permitted to terminate at a top enclosure complying with Section 713.12.
3. Supporting construction for 1-hour fire barriers required by Table 509 in buildings of Type IIB, IIIB and VB construction is not required to be fire-resistance rated unless required by other sections of this code.
4. Interior exit stairway and ramp enclosures required by Section 1022.2 and exit access stairway and ramp enclosures required by Section 1009.3 shall be permitted to terminate at a top enclosure complying with Section 713.12.

So 713.12 states:

713.12 Enclosure at top.
A shaft enclosure that does not extend to the underside of the roof sheathing, deck or slab of the building shall be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.


With the cycle going full circle without clarification; I think this is the intent.

If the shaft terminated at the roof deck and did not extend above the roof surface, I would say stop the rating at the roof deck

However, the intent of this section is to provide protection for a shaft.(stair shaft, elevator shaft, chase way, etc.) , so if the wall continues above the lower roof line and extends up a story (elevator penthouse), I would believe that the elevator shaft walls must be continuous until it reaches the up most roof deck for termination.

Section 1509.2.5 may address the penthouse structure you are describing better.
1509.2.5 Type of construction.
Penthouses shall be constructed with walls, floors and roofs as required for the type of construction of the building on which such penthouses are built.

Exceptions:
1. On buildings of Type I construction, the exterior walls and roofs of penthouses with a fire separation distance greater than 5 feet (1524 mm) and less than 20 feet (6096 mm) shall be permitted to have not less than a 1-hour fire-resistance rating. The exterior walls and roofs of penthouses with a fire separation distance of 20 feet (6096 mm) or greater shall not be required to have a fire-resistance rating.
2. On buildings of Type I construction two stories or less in height above grade plane or of Type II construction, the exterior walls and roofs of penthouses with a fire separation distance greater than 5 feet (1524 mm) and less than 20 feet (6096 mm) shall be permitted to have not less than a 1-hour fire-resistance rating or a lesser fire-resistance rating as required by Table 602 and be constructed of fire-retardant-treated wood. The exterior walls and roofs of penthouses with a fire separation distance of 20 feet (6096 mm) or greater shall be permitted to be constructed of fire-retardant-treated wood and shall not be required to have a fire-resistance rating. Interior framing and walls shall be permitted to be constructed of fire-retardant-treated wood.
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Thank you both very much. This is very helpful.

Follow up question: Would the portion of the elevator shaft wall above the existing building roof need to be insulated since it is now on the exterior of the building? I'm assuming it would but would appreciate another's opinion.

Thanks.
 
On the follow up question... IF the elevator is designed for installation in an 'unconditioned' environment then it is possible that lesser insulation could work. Of course, the gaping hole in the existing roof deck you will create to extend the shaft may well shift the thermal envelope to include the shaft enclosure, unless you can 'thermally isolate' the shaft enclosure (and I'm not sure you can...).
 
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