Construction Type for Exit Stair Tower

[Mr Softy]

I have my ideas, but I'd like to hear other opinions.

5-story pedestal building.
1st Floor Type IB; 4 Floors Type VA - max for the Use Group, R-2

Stair towers are 5 story.

What construction type for the towers?

 

[RLGA]

If you are using the horizontal separation allowance per IBC Section 510.2, then the building below the horizontal separation is required to be Type IA construction and not Type IB. Refer to subparagraph #3 of that section in order to determine the requirements for stairway enclosures and shafts. The construction of the enclosures and shafts can be of the construction type permitted for the building above the horizontal assembly and, of course, Type IA construction for the building below the horizontal assembly. In your case, the rating will need to be 2-hour fire barriers and the exception in that Section would not apply since you are more than 4 stories overall.

 

[classicT]

If you are using the horizontal separation allowance per IBC Section 510.2, then the building below the horizontal separation is required to be Type IA construction and not Type IB. Refer to subparagraph #3 of that section in order to determine the requirements for stairway enclosures and shafts. The construction of the enclosures and shafts can be of the construction type permitted for the building above the horizontal assembly and, of course, Type IA construction for the building below the horizontal assembly. In your case, the rating will need to be 2-hour fire barriers and the exception in that Section would not apply since you are more than 4 stories overall.

Boom... Ron is da man. Right on. I'd only add that the lowest level of Type 1A Construction must be sprinkled per #5.

If you want to review the code section, here you go.

510.2 Horizontal Building Separation Allowance
A building shall be considered as separate and distinct buildings for the purpose of determining area limitations, continuity of fire walls, limitation of number of stories and type of construction where all of the following conditions are met:

1. The buildings are separated with a horizontal assembly having a fire-resistance rating of not less than 3 hours.
2. The building below the horizontal assembly is of Type IA construction.
3. Shaft, stairway, ramp and escalator enclosures through the horizontal assembly shall have not less than a 2-hour fire-resistance rating with opening protectives in accordance with Section 716.5.
   Exception: Where the enclosure walls below the horizontal assembly have not less than a 3-hour fire-resistance rating with opening protectives in accordance with Section 716.5, the enclosure walls extending above the horizontal assembly shall be permitted to have a 1-hour fire-resistance rating, provided:
   1. The building above the horizontal assembly is not required to be of Type I construction;
   2. The enclosure connects fewer than four stories; and
   3. The enclosure opening protectives above the horizontal assembly have a fire protection rating of not less than 1 hour.
4. The building or buildings above the horizontal assembly shall be permitted to have multiple Group A occupancy uses, each with an occupant load of less 300, or Group B, M, R or S occupancies.
5. The building below the horizontal assembly shall be protected throughout by an approved automatic sprinkler system in accordance with Section 903.3.1.1, and shall be permitted to be any occupancy allowed by this code except Group H.
6. The maximum building height in feet (mm) shall not exceed the limits set forth in Section 504.3 for the building having the smaller allowable height as measured from the grade plane.

 

[north star]

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Mr. Softy

Long time no see !.......Glad to see you remembered
this Forum.

I encourage you to come and participate more often.

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[mtlogcabin]

Mr. Softy

Long time no see !.......Glad to see you remembered
this Forum.

I encourage you to come and participate more often.

Ditto the comment. I always enjoyed reading your opinions on the codes sometimes different sometimes similar but always get me thinking.