Fire-Treated Wood 3

[BSVBD]

I have an assembly building that requires the exterior bearing walls to be a fire-rated assembly.

Where can i find adjustment factors for fire-treated sawn lumber AND OSB Sheathing. I've used NDS Table 4B for Preservative-Treated wood. Is there a similar NDS reference that i am over-looking?

Thank you!

 

[jayrod12]

Does it need to be fire rated lumber, or just a fire rated assembly? Two different animals.

 

[BSVBD]

jayrod12 - IBC 602.3 Type III construction in which the exterior walls are of non combustible materials... Fire-retardant-treated wood framing complying with Section 2303.2 shall be permitted within exterior wall assembles of a 2-hour rating or less.

 

[jayrod12]

Wouldn't it be cheaper to do with light gauge steel studs then?

Around here if I were to ask for fire rated lumber the cost would likely outweigh LGS

 

[BSVBD]

jayrod12 - The architect makes the decision what type of assembly we will use. I need to engineer it. If it doesn't work, i will tell him. At this point, the question remains:

Where can i find adjustment factors for fire-treated sawn lumber AND OSB Sheathing. I've used NDS Table 4B for Preservative-Treated wood. Is there a similar NDS reference that i am over-looking?

Thank you!

 

[Wallache]

The manufacturers have the adjustment factors in their ICC reports.

 

[mike20793]

Unfortunately, architects like to try and get 2 hour rated walls with wood studs. Hopefully you don't have to balloon frame it! See Link for the reduction factors that I use.

 

[BSVBD]

Wallache - Thank you! Your information lead me to obtain the ICC report from Hoover Treated Wood Products, Inc, which was advertised within the UL Design No. we are using.

mike - Thank you. Your information may very well come in handy in the future! Balloon framing not necessary for this 1-story building.

Thank you you all!

 

[Sawbux]

Make sure you check the corrosion vs. fasteners. Some fire retardants are very corrosive to normal steel nails & hardware.

 

[BSVBD]

Sawbux -
Thank you for the caution advice. I did check with the Fire-Retardant-Treated Wood Impregnator. They sent a Technical Note stating that their "...treatment is not significantly more hygroscopic that untreated wood."

It certainly is the responsibility of our firm to determine for ourselves a comfortable definition of what is the assumed magnitude of "not significantly more". In our case, since the rated wall system will be confined within the building envelope, we are comfortable with the verbage of proprietary note.

For what it's worth for anyone in the future, It appears as though fire-treated sawn lumber and wall sheathing with carbon-steel fasteners may be a reasonably design-efficient fire assembly.

Due to the efficient service and information, to include an ICC, ESR report and more than one Technical Note within minutes of request, I would like to share the name of the proprietor, but, i understand that this may be considered as promoting which is against Posting Guidelines, which i DO respect. Therefore, i will post the question in another post to see if this incidental, inadvertent promotion, intended solely for the purpose of assistance to other engineers, would be considered as acceptable.

Thank you all for your assistance!

 

[andriver]

I just read this but have used Hoover Treated Products and have been happy with their service in regards to technical questions.

One question I had for them was whether I needed to use an incising adjustment factor for their fire treated wood, but was informed that they are pressure treated and just need to apply a coefficient to my NDS values.