# Turning an existing wall into a rated wall



## Mech (Feb 19, 2014)

2009 IBC w/ 1012 IBC Chapter 11

2000 NFPA 101 - Life Safety Code

I need to create a smoke partition with a 30 minute fire rating.  There is an existing 2x4 stud wall with (1) layer of 1/2" gyp board on each side.  The construction was performed in 1990; the drawings are dated January, 1990.  Assuming the studs are on 16 inch centers, can I call this a 35 minute rated wall per the 2009 IBC?  Or does gyp board produced in 1989 -1990 have a different fire resistance than the gyp board of today?  The existing gyp board may or may not have been water resistant, if that makes a difference.

*721.6.2 Walls, floors and roofs.* These procedures apply to both load-bearing and nonload-bearing assemblies.

*TABLE 721.6.2(1) TIME ASSIGNED TO WALLBOARD MEMBRANES**a, b, c, d*


*DESCRIPTION OF FINISH**TIME**e** (minutes)*NOTE: SEVERAL

LINES OF THIS

TABLE WERE OMITTED

3/8-inch gypsum wallboard101/2-inch gypsum wallboard155/8-inch gypsum wallboard301/2-inch Type X gypsum wallboard255/8-inch Type X gypsum wallboard40Double 3/8-inch gypsum wallboard251/2-inch + 3/8-inch gypsum wallboard35Double 1/2-inch gypsum wallboard40


For SI: 1 inch = 25.4 mm.

a. These values apply only when membranes are installed on framing members which are spaced 16 inches o.c.

b. Gypsum wallboard installed over framing or furring shall be installed so that all edges are supported, except 5/8-inch Type X gypsum wallboard shall be permitted to be installed horizontally with the horizontal joints staggered 24 inches each side and unsupported but finished.

c. On wood frame floor/ceiling or roof/ceiling assemblies, gypsum board shall be installed with the long dimension perpendicular to framing members and shall have all joints finished.

d. The membrane on the unexposed side shall not be included in determining the fire resistance of the assembly. When dissimilar membranes are used on a wall assembly, the calculation shall be made from the least fire-resistant (weaker) side.

e. The time assigned is not a finished rating.

*TABLE 721.6.2(2) TIME ASSIGNED FOR CONTRIBUTION OF WOOD FRAME **a, b, c *


*DESCRIPTION**TIME ASSIGNED TO FRAME (minutes)*Wood studs 16 inches o.c.20Wood floor and roof joists 16 inches o.c.10

For SI: 1 inch = 25.4 mm.

a. This table does not apply to studs or joists spaced more than 16 inches o.c.

b. All studs shall be nominal 2 × 4 and all joists shall have a nominal thickness of at least 2 inches.

c. Allowable spans for joists shall be determined in accordance with Sections 2308.8, 2308.10.2 and 2308.10.3.



Thanks


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## BayPointArchitect (Jun 18, 2014)

1/2" gypsum wallboard (non-rated) = 15 minutes

2 x 4 studs at 16" o.c. = 20 minutes

1/2" gypsum wallboard (non-rated) = 15 minutes

Total wall assembly = 15 + 20 + 15 = 50 minutes

50 minutes > 30 minute required fire rating = okay

At least that is how I have been doing it.


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## JBI (Jun 18, 2014)

Mech, Pretty sure it will work... The section you provided is a _new_ construction prescriptive method - read as 'conservative' method. Just curious why the EBC is not being used for this? It is an existing building after all... Also, the current UL manual or USG manual would give you plenty of design options for the wall (many 1 hour walls allow single layer plain GWB). Don't forget to address any penetrations, membrane and through penetrations, that exist or will be created. Also, as a _'smoke partition' _the assembly is not expected to have much of a fire resistance rating anyway.


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## Frank (Jun 18, 2014)

As to rating you are there.

Big work on smoke partition is sealing penetrations and putting in smoke dampers.


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## steveray (Jun 18, 2014)

JBI.....I believe it is because it is a "newly" rated wall....The IEBC or NFPA101 would give you the requirement for rating it...The quoted section(s) would say how...


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## JBI (Jun 18, 2014)

steveray -

You are correct, but there is also 'Resource A' at the back of the EBC which is modeled after (a reproduction of?) the HUD guidelines for Fire Ratings of Archaic Materials and Assemblies. The tools in that resource will allow assignment of ratings for existing assemblies as well as prescriptive means to increase ratings.

The OP is a good case for application of those methods, though the end result is likely the same.

Older assemblies like wood lath and plaster can also be evaluated in Resource A.


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## fatboy (Jun 18, 2014)

JBI, no one has mentioned, but glad to see you hanging around more now..............


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