Looking to confirm that a fire-blocking wall of an attached garage needs drywall on both sides extending into the attic. See diagram below.
If the red section is not sheetrocked, then wouldn’t it defeat the fire rating since on the opposite side there is a living space and not the matting building’s attic?
http://s21.postimg.org/8bf085ncn/Screen_Shot_2015_03_21_at_6_25_38_PM.png
(ceiling in the matting living space is not shown, though it is where the “Top Plate” is labeled.)
I believe so, I am not sure if it states this in the IRC. But when you do townhouses they are required to be 5/8 X firewall rated drywall which is taped and mudded.
No, 5/8" drywall is installed on the ceiling then walls. You run the drywall up to the roof sheathing if two residential units are connected, such as a townhome.
So in a single-family home (this is, I should have specified) the diagram is typically correct according to IRC?
The garage is completely rocked, taped, and mudded.
No. And the sheetrock on the wall is not required to be 5/8 type-X. 1/2 inch will do. Type-X is required for the ceiling only if there are habitable rooms above (be careful on the definition of habitable room). See TABLE R302.6 DWELLING/GARAGE SEPARATION
Am I correct in assuming that because the garage’s walls and ceiling is “sealed” by drywall and tape the fire-blocking is maintained?
This all came up in relation to a sub panel placed in the fire-blocking wall sheetrocked top,bottom, and back but not on the sides no room since the box is tight to the 2x6’s.
http://s29.postimg.org/fy334totj/Screen_Shot_2015_03_23_at_9_29_10_AM.png
Chuck is correct 1/2" for walls but last year the building department in one community I did a draw inspection for required 5/8" on the wall.
Another community required 2 layers of 5/8" in a garage ceiling with a bedroom over it. All ductwork chases were required to be 5/8" regardless. Type x was not specified but was installed.
Also, the area you describe is sometimes foamed or packed with fiberglass. Whatever the inspector wants or is easiest to apply.
It would unusual in this area for an inspector to allow 1/2" on a garage wall unless it was fire rated, most contractors here would just do 5/8" since its easier to order all the same rock for the garage.
I agree with Chuck.
Here is the code from the IRC.
SEPARATION
MATERIAL
From the residence and attic- Not less than 1⁄2-inch gypsum board or equivalent applied to the garage side
From all habitable rooms above the garage-Not less than 5⁄8-inch Type X gypsum board or equivalent
It is not called fire blocking by they way. That is something else.
Wisconsin Rules
Fire blocking is a framing term I believe referencing the use of materials to block the flow of air/smoke. Correct? The correct reference would be calling the wall fire-rated correct?
I have seen the terms fire-blocking/firewall/fire-rated thrown around hap-hazardly online a lot the past week researching the topic. Short story an electrical design was approved, permit issued, then a follow-up inquiry resulted in the submitted design being rejected (after drywall cut). Frustration followed.
Now it looks like I am going to create an alcove in the fire-rated wall and place a smaller load center in there. Going smaller is due to not being able to fit the 14.5" load center in there with 5/8" drywall on both sides of the framing members.
I do wonder what the permit approving inspector thought I meant in the detailed sketch of the area and work by the words “flush mount”, “garage”, and “living space”. 
Well that settles that.
And Mike, what do you do if the code inspector has a different opinion.
Last year I built a deck that was engineered with Diamond Pier footings, I provided all the specs from the factory and was not allowed to use Diamond Pier footings. Unless, my deck was less than 4’ X 6’ ???
Were not code inspectors by the way, I have the 2012 book in my truck but only use it for refernce.
No, “fire rated” is also incorrect. Fire Separation is the correct term.
I like this standard. It lays it out pretty clearly.
So if the wall is also sheetrocked on the house interior 1 layer of 1/2 inch will do. Just don’t put a PEX manifold in the wall facing either side.