Mechanical Information

This page provides code information for mechanical systems and installations. The prevailing Code for mechanical installations is the Florida Building Code, Mechanical.  

All permitted work shall be inspected. Inspections may be requested by permit holders online via the permitting portal or by calling (866) 957-3764, Option 5.

The information below is an overview of most commonly missed items during Residential inspections but is not an all-inclusive list.

FBC (R M) 1602.2 Note 4 

Return air shall not be taken from a closest, mechanical room, or furnace room.

FBC (M) 505.1 

Domestic kitchen exhaust shall be smooth inner walls.


FBC (Energy) R403.3.2 

Mechanical Closest Sealing mandatory constructed and sealed in accordance with section C403.2.9.2   All joints between air barriers of walls, ceiling, floor, and door framing as well as all penetrations of air barriers shall be sealed to form airtight passageway.


FBC (R M) 1601.4.4

Support field, shop metal, and flex duct shall be supported to SMACNA HVAC standards.


FBC (RES) M1601.6 

Furnace supply air to living space cannot supply to garage.


FBC (R) M1411.7   

Refrigerant pipe within 1.5” of roof deck shall be protected


FBC (RES) R318 

Cannot have expanding foam within 6” of the ground “terminate protection”.


FBC (Energy Table) R402.4.1.1 and R403.3.2 

Require the mandatory sealing of all ducts, filter boxes, air handlers, and building cavities.


FBC (Energy) R403.4  

Pipes/ condensate must be insulated when they carry any liquid under 55 or over 105


FBC 306.4.1 

Light switch at opening and by appliance in attic. 


FBC (R) 1602.3  

Balanced return air need transfer and 1” undercut.


FBC (Mech) 406   

Uninhabited spaces (crawl space attic) must have natural or mechanical ventilation.


FBC (R) (Table M) 1506.2   

Shows need 4” flex on fans unless pipe 3” is used and max is 5 feet.

Manufactures such as Amana, Whirlpool, Maytag, etc., require dryer vent to terminate 12” above ground.


FBC (M) 603.9 181b 

Tape on flex.  181 a-h for heat sensitive.


FBC (M) Table 401.5  

Vent on residential .25” minimum; 0.5” max screen size.


FBC (M) 802.8   

Insulation shield passing thru an insulated assembly.


FBC (R) 318.5

Condensate outside of homes 12”.


FBC (Energy Con) (R) 403.6  

Outdoor air and exhaust have automatic damper or gravity damper.


FBC (M) 302.3.2  

Stud notching 25% exterior and 40% nonbearing wall.

SECTION 304 Gas Code – Combustion Air (Residential)

One hole opening within 12” of top needs one square inch per 3000 BTU.

Two holes openings:  one within 12” of the top; one within 12” of the bottom one square inch per 4000 BTU.

Diameter of pipe divided in half times pi.  For example, 6” pipe 3.14 x (3x3).  Square duct is side x side.

One hole opening:  4” max 37,000 BTU, 5” max 58,000 BTU, 6” 84,000 BTU.

Two hole opening:  4” max 50,000 BTU, 5” max 78,000 BTU, 6” 113,000 BTU.

FBC(R) G2407.5 can not use a louvered door for combustion air.

FBC(R) 304.11 note 5 no screens on combustion air in attic.