AskCodeMan

Separation between garage and habitable room on the second floor, min. 5/8 type X ? FBC.

Hi Richard,

I believe you are asking about the FBC, Residential code separation requirements.

Yes, separation is required between the garage and the dwelling unit on the wall between them, and separation between the garage and the dwelling units attic - which can be achieved either by running the separation wall all the way to the roof sheathing or by installing a ceiling in the garage.

The minimum separation for the above is 1/2 inch gypsum board.

However, you expanded on the separation issue by having a habitable space above the garage, in which case, yes, the ceiling is required to be 5/8 inch Type X gypsum board minimum AND the structure supporting the habitable space is also required to be protected - but only requires 1/2 inch gypsum board.

Think of it this way - two options:
- There is a dwelling unit with an attached garage and:
- - a) There is no habitable space above the garage - the wall separating the garage from the dwelling unit AND the ceiling (the most often chosen option rather than to continue the wall up to the roof sheathing) would be required to have a minimum of 1/2 inch gypsum board applied to the garage side. There is no requirement to install any wall covering material on any of the other walls of the garage, they could be open stud walls.
- - b) There is habitable space above the garage - the wall separating the garage from the dwelling unit is required to have a minimum of 1/2 inch gypsum board applied to the garage side; AND the ceiling between the garage and the habitable space above is required to have a minimum of 5/8 inch Type X gypsum board applied to the garage side; AND the other garage wall which are supporting the habitable space above the garage are now required to also have a minimum 1/2 inch gypsum board applied to the garage side ... because those walls are structurally supporting the habitable space above.

You may find the option to run the wall separating the garage from the dwelling unit from the slab all the way to the roof sheathing, with minimum of 1/2 inch gypsum board on the garage side. If you did, the garage would not be required to have a ceiling, it could be open trusses/framing. I doubt you will find that, but keep it in mind as you might - I've only seen it done a couple of times, and then it was done incorrectly as that would be required to seal off all the way soffit-to-soffit with the 1/2 inch gypsum board taped and finished to at least a level 2/3 finish - see this question and answer for more information on the finish level required: (note: put cursor over link, right click, select 'Open in New Window') viewtopic.php?f=22&t=67 .

Codeman