When is a fire wall required, commercial and residential?

Originally Posted By: Rich Clos
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My boss can’t answer me when I ask “when” does a room needs to have a fire rated wall. The usual answer is, ‘the designer required it’, or ‘its on the print’.

I just saw a furnace put into a hallway closet at a church, 2x4 studs, drywalled on the outside only. Its a residential forced air furnace, wouldn't this require a fire rated wall? This topic is confusing to me.


Originally Posted By: Ryan Jackson
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Thats a difficult question to answer, as a lot of things can sway the answer. IF it is over 400,000 BTU input, you will have an incidental use area and have to fire rate it, unless the building is sprinkelered, in which case the room must only be resistant to the passage of smoke. If it is greater than 10% of the major use, it might be an accessory use and therefore have to be rated. If it is a different use than the major use, you will have a mixed occupancy building and may have to rate it, depending on whether the building was justified as seperated use (sum of the ratios method) or non seperated use with the most restricitve type of construction governing the type of construction as well as maximum height and area.

I would just make sure you are looking at the approved plans (the ones the city reviewed) and not neccasarily the desginer's plans. Remember that the only person that is legally allowed to determine use and occupancy is the building official...not the registered design professional.

Ryan Jackson, Salt Lake City