3 Hour Firewall Cracking

[indyarchyguy]

A project that was constructed approximately 18 months ago in Indiana (2012 IBC with 2014 amendments). A warehouse has 3-hour firewalls that sit on top of a concrete curb of approximately 12-inch height from the top of the floor. The walls have started cracking in three different locations (see photos from GC). Walls were constructed with 6-inch studs and extend approximately 19 feet in height. The contractor is asking why. There are two different walls. One wall is approximately 150 feet in length and the other 90 feet. They told me they lapped the joints of the three layers of drywall. My impression is they did not provide control joints at the 30-foot maximum length as required. Would this make sense to you?

 

[Inspector Gift]

Can you confirm they used tape under the mud?

 

[Sifu]

Control joints and head or bottom of wall joints/slip joints (dynamic?) would be an easy first guess. Check the plans to see if the FRR joints are specified and if it is specified for movement (sometimes they will be in a deferred firestop submittal). Plans may (should have?) also specify the control joints.

 

[Plumb-bob]

I am not sure of the answer, but have some questions:

1) Could control joints be used and maintain the integrity of the fire separation?
2) What type of drywall tape was used? Mesh or paper?
3) Does the assembly include plywood or other rigid sheathing under the drywall?

 

[Plumb-bob]

Can you confirm they used tape under the mud?

Yes, it does look like there is no tape.

 

[Sifu]

I am not sure of the answer, but have some questions:

1) Could control joints be used and maintain the integrity of the fire separation?
2) What type of drywall tape was used? Mesh or paper?
3) Does the assembly include plywood or other rigid sheathing under the drywall?

1) A FRR control joint would need to be used. A 3-hr joint may require an engineering judgment.

 

[steveray]

Betting that it is built wrong in at least a few ways.....Got a ul#?

 

[Inspector Gadget]

Certainly looks like it wasn't constructed properly. (Exhibit A for "why Inspector Gadget requires inspection of fire-rated assemblies *before* application of drywall compound.")

 

[JPohling]

Slip track at connection to roof structure?

 

[TheCommish]

What gauge steel studs?
How is the wall attached and detailed at the roof, not just slip track, is there overlapping sheetrock at the top?