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Interpretation #5781

Original Request

  • Date: July 18, 2008
  • Requested By: Joe Marconi
  • Requester E-Mail: JMarconi1812@yahoo.com
  • Code Version: 2004
  • Code: MECHANIC
  • Code Description: Mechanical
  • Chapter: 4
  • Section: 402
  • Topic: Common bath exhaust fan

  • Question: Is it the intent of 402.3.1 to allow 1 bath fan located in toilet room to draw exhaust air from an adjacent shower area(separated by a pocket door) through a 1"x36" undercut in that door provided the fan is of adaquate cfm for both spaces.

Answer on 07/18/2008 at 8:01 AM

Let's step through this. Step 1) FBC-M 402.3.1 directs you
to Section 403 if choosing to use mechanical ventilation.
Step 2) FBC-M, Table 403.3 requires that toilet rooms and
bathrooms (Dwelling Occupancy) be provided with a
mechanical exhaust system capable of providing 50 cfm
intermittent or 20 cfm continuous. Next to the toilet room
requirement there is a refernce to letter "g", (located
below table 403.3.) Step 3) Letter "g" states, transfer
air is permitted in accordance with Section 403.2.2. Step
4) Under 403.2.2 makeup air for required exhaust systems
in spaces such as baths is allowed. Conclusion: The 36sq.
in. of undercut door to be the path for the 25 to 50 cfm
should satisfy the requirement for this toilet room.

Commentary:

As requested, this answer is based on the Florida Building Code - Mechanical. An assumption is being made to provide the answer that the Florida Building Code - Mechanical applies and not the Florida Building Code - Residential.