In our permitted plans we have a 2 hour fire wall. It is designed with standard wood studs and two sheets of 5/8" drywall on both sides. I have been told that of we use steel studs and fire resistant insulation that we can reduce the drywall requirements. When I called the planning department they told me there is information from UL on different ways to achieve a two hour wall but they were far to busy to even tell me the name of the book they use as reference material on this. Does anyone know where I can get the UL standards for a two hour firewall?
UL Requirements For 2 Hour Wall
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USG Gypsum Construction Handbook "centennial edition".
Page # 326 2-hr. Rating UL Design U301 Drywall System 2 X 4 wood studs 16" O.C. 2 layers each side.
Page # 328 2-hr. Rating UL Design U411 , U412 , or U419 Drywall System
2 & 1/2 Metal Studs 25-ga. 2 layers both sides.
Page # 326 2-hr. Rating UL Design U301 Drywall System 2 X 4 wood studs 16" O.C. 2 layers each side.
Page # 328 2-hr. Rating UL Design U411 , U412 , or U419 Drywall System
2 & 1/2 Metal Studs 25-ga. 2 layers both sides.
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IMO, you should build what you have permitted.
If you think you are going to save a bit of money by changing the design at this stage, you may be wrong. Depending on what the AHJ requires of you to officially submit the alternative design, you might see those anticipated savings wiped out.
If you think you are going to save a bit of money by changing the design at this stage, you may be wrong. Depending on what the AHJ requires of you to officially submit the alternative design, you might see those anticipated savings wiped out.
It’s not about saving money. The two hour walls in question are built out of heavy gauge 8” girts provided by the pre engineered steel building supplier but on our floor plan it shows wood with two sheets of 5/8” drywall on both sides. I was told by a local framed/drywall guy that with the existing steel and using fire resistant insulation I won’t need the two layers of drywall. When I called the planning department they said I will have to submit the change of plans with UL justification for meeting the two hour wall. I am just looking for the documentation.
Also, I appreciate the excerpt from the gypsum construction manual but I presume the planning department will want it straight from UL.
Also, I appreciate the excerpt from the gypsum construction manual but I presume the planning department will want it straight from UL.
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You can use a UL manual for fire resistive construction. Or you can use a similar manual from the Gypsum Association or Factory Mutual or other manual of tested assemblies. There is more to it than just drywall. The manual will explain sheet orientation, framing, joint offset, fastener spacing, joint treatment, etc. The inspector will look in the book you choose at the assembly you submit to inspect it. Then he will know if it is built properly. If I were the inspector, I would also require a submittal for your treatment of penetrations through that wall.
Here is a link for us fire rated assemblies. Scroll Fast way down till you get to the 2 hour section and then search out the assembly you are planning.
https://www.usg.com/content/usgcom/en/design-studio/assemblies.html
https://www.usg.com/content/usgcom/en/design-studio/assemblies.html
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I don't recall a 1 wythe stud partition getting 2hrs with little mass of gyp board. Usually the number of layers of drywall do not dicate what type of wall construction, it's pretty cheap. The stud type and size is what is defining.
Any permit drawing for a rated wall should have that designation on the plans, if not, you will be requested for the paperwork during review. For instance, "2hr wall per UL U419" or "5/8" Type X G.B. with fire taped joints". The UL assemblies are VERY specific in their construction as they were tested, so there are no 3 or 4 assemblies that generally cover any situation.
Use the USG link given by ront. I believe UL resources, which are much more detailed than USG's, are accessed only by professionals, unless you want to buy the book.
Any permit drawing for a rated wall should have that designation on the plans, if not, you will be requested for the paperwork during review. For instance, "2hr wall per UL U419" or "5/8" Type X G.B. with fire taped joints". The UL assemblies are VERY specific in their construction as they were tested, so there are no 3 or 4 assemblies that generally cover any situation.
Use the USG link given by ront. I believe UL resources, which are much more detailed than USG's, are accessed only by professionals, unless you want to buy the book.
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