Mike NY wrote:We are designing a new project located in Mamaroneck, NY. It is a 4 story mixed use building. It is a R-2 IIIB Construction. The interior is sprinkled. We need to put windows in a wall that is located 3'2" from the side property line. The total wall opening % for the windows is around 22%. The approach we are taking to get to less than 15% protected openings is to make most of the windows 45 minute fire-rated assemblies and for the remaining windows to be 1 hour rated assemblies so that these can qualify as a wall and not count as an opening. Is this the right approach in regards to the fire-ratings? We are trying to use steel frame windows made by Optimum.
Thanks.
The following is from the 2010 New York State Building Code on the ICC site: (bold and underlining are mine)
(
http://publicecodes.cyberregs.com/st/ny ... 010-999999 )
- 702.1 Definitions
- -
FIRE SEPARATION DISTANCE. T
he distance measured from the building face to one of the following:
- - - 1.
The closest interior lot line;
- - - 2. To the centerline of a street, an alley or public way; or
- - - 3. To an imaginary line between two buildings on the property.
- - -
The distance shall be measured at right angles from the face of the wall. - 704.2 Projections.
- - I presume you meet the requirements and limitations of this section.
- 704.5 Fire-resistance ratings.
- - I presume the exterior wall is fire-resistance rated from both sides per this part of this section: "The fire-resistance rating of exterior walls with a fire separation distance of 5 feet (1524 mm) or less shall be rated for exposure to fire from both sides."
- 704.8 Allowable area of openings. The maximum area of unprotected or protected openings permitted in an exterior wall in any story shall not exceed the values set forth in Table 704.8.
Where both unprotected and protected openings are located in the exterior wall in any story, the total area of the openings shall comply with the following formula:
- - (see code for formula, note that the percentage is based on the exterior wall area of any story and not of the entire exterior wall area)
- Table 704.8 Maximum Area Of Exterior Wall Openings a (note a says: a. Values given are percentage of the area of the exterior wall.)
- - Fire Separation Distance of Greater than 3 feet up to 5 feet - unprotected openings: "Not permitted" c (note c says "c. For occupancies in Group R-3, ... " which means note c is not applicable because you are working with a Group R-2 occupancy.) - end result is that no unprotected openings are permitted ... unless your sprinkler system meets 903.3.1.1 (see below).
What type of sprinkler system are you using?
I ask because: 704.8.1 Automatic sprinkler system.
In buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1,
the maximum allowable area of unprotected openings in occupancies other than Groups H-1, H-2 and H-3
shall be the same as the tabulated limitations for protected openings.
903.3.1.1 is a full NFPA 13 sprinkler system. If the sprinkler system you are using is an NFPA 13R then there is no allowable calculating the unprotected openings as protected openings. And because the occupancy is R-2, no unprotected openings are permitted.
It is easy to lose track of where one is in these reviews, if I missed something or the above does not compute (such as 2+2=5) let me know and I will go back through it.