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I'm building my first over/under duplex. Floor/ceiling assembly of the lower unit needs to be fire rated. IRC 302.3.1 says the walls that support the floor/ceiling assembly need the same rating.
Do the supporting walls have to be rated on both the interior AND exterior sides? If the fire ratings are meant to protect the upstairs unit from a fire in the downstairs unit, then I would think the walls only need the rating from exposure on the interior. Any input appreciated.
Do the supporting walls have to be rated on both the interior AND exterior sides? If the fire ratings are meant to protect the upstairs unit from a fire in the downstairs unit, then I would think the walls only need the rating from exposure on the interior. Any input appreciated.
