Firewall questions on garage

Hello to all, I would very much appreciate some garage firewall code info on this:

I have a 20x20 attached 2-car garage which I built 4 years ago which has a guest room above it, the room upstairs is also attached to the house with both a 2nd floor exterior exit and a hallway to the house. No garage stairs needed. The garage level has 2 manual garage doors (metal), one rear 32" metal exit door with a window which leads to the outside, and two 32" metal doors with no windows which lead into the house on the first floor.
To rent out the guest room, I need to add a firewall of 5/8" type X sheetrock to the garage ceiling and walls. To cover all bases before I get it inspected, I have several questions. I live in NC near Asheville, but not in the city limits.

1 - Due to the guest room being above the garage, I believe I need to install the firewall sheetrock on all 4 walls in addition to the ceiling, not just the wall abutting the house. Is this correct?

2 - The garage has 9 pressure treated 6x6 posts holding up the upper floor, one in each corner, one in the center of each of the 4 walls, and one in the very center of the garage (which has a gravel floor). On the walls, these jut into the garage a few more inches than the main studwalls. Do I need to cover these "jut-outs" with vertical strips of type X sheetrock as well? The center post too?
If so, then will I also need to cover the triple-thickness 2x10 beam assembly running on the garage ceiling from front to back holding up the crosswise floor joists at their center point (extending 9 1/2 inches lower than where the main ceiling drywall will be and resting on the center post)?

3 - Around the perimeter at floor level, the lowest PT sill studs are nailed into horizontal floor-level 6x6 posts as well, which are attached with heavy "T" brackets to all the vertical 6x6 posts (which all have concrete footers below ground level). Need these ground-level sill 6x6's be covered as well (with an inch or so of concrete), so that no wood is showing?

4 - Most of the wiring in the garage is romex, and in many areas will pass through a hole in the drywall when need be, which will be sealed with joint compound. Some will be covered by the drywall at ceiling level with furring strips to create a channel space for the wiring. I assume romex is OK. There is some BX as well.

5 - In the back of the garage is a vertical 4" PVC pipe a foot from the rear wall which runs from the ceiling to underground (coming from the upstairs toilet). Do I have to fabricate a square column around this and cover it with vertical strips of type X sheetrock too?

6 - Do the metal doors leading to the house (no windows) need to be self-closing? These are the metal Stanley-type ($150 range) entry doors and are pre-hung with wood frames. Do the wood frames present a problem?

7 - The lowest couple of inches inside the garage may occasionally get moisture in a heavy rain, can I use green bathroom-type sheetrock (1/2") for this or must it be type X as well, and 5/8"?

8 - On the walls, can I mount the sheetrock sideways (8' wide, 4' vertical) or is this frowned upon. In this case, would I need to build up the lowest edge at the bottom (and topmost ceiling edge) with joint compound to make it thicker?

9 - Being in NC where the climate is decent, do I need to put insulation in the garage ceiling rafters when I install the ceiling firewall (below the upstairs guest room floor), or can I opt out on this, as it's not really a big help here?

Thanks, guys. This will be a much appreciated help if I get all this done right and get it passed on the first try.

1. It would be better to cover all 4 walls in 5/8.

2. Just a suggestion, fur out the walls to match flush with the face of the 6x6s. The beam also has to be covered. Some contractors use the beam to hide ductwork and wiring, plumbing, etc.

3. The sill plate 6x6s could be covered when you do the walls if you build the walls out flush. (not really sure on that one.)

4. Wiring does not need to be exposed, especially romex.

5. A column for the pipe would be best.

6. In Kentucky, they would not have to have closers, I don't know about NC.

7. Good question, most garages around here have at least 1 row of concrete blocks around the exterior walls and 2 blocks at the house.

8. 90% of new construction goes in horizontal. The top will have to be built up with compound, the bottom would be better if it was built up also.

9. If you can afford it, it would be better to insulate all of it, but definitelty, the ceiling.



Inspector D.....? You got anything?

as far as the doors in WA. they need to be a 20 min. rated assembly (door and jamb) that self closes. look at the top or inside edge of the door and see if it has a fire rating on it. Codes will vary check with the code wizzard in NC

Thanks for replying, Square Eye, your posts have come up in several Google searches I've done in the past, I've visited your site as well. I've been into Home Improvement on my own places I've owned since 1980, also built a few cabins and have done work for others off & on. Got many of my engineering and "eye" skills from my dad, too. My most pro area is electrical, as I always pass code on this work on the first shot, my carpentry structural sense is by instinct, always using a bit of overkill on weight, beams, posts, etc., but never worked construction for a living except 1 year as a roofer in the 80's. 90% of my work has been on my own homes.
Back to the topic (including 4 more hours of web search)...
1 - That's my take on this, all 4 walls plus the ceiling in 5/8" type X
2 - Either fur out or cover the posts
3 - May have to call county on this one, if I did cover them, the drywall would go down to gravel level, if they did need it to be covered, I was thinking of putting a form about 2" from these 6x6 sills and pouring concrete to cover them, not a big hassle. Then the bottom of the drywall would be a bit higher, where the actual stud sill & verticals start.
4 - Most wiring (most now is near or at the level just before the ceiling) would be covered, except where it dropped to a lower level on the walls and couldn't be under the drywall. I would remove the staples to make it look like it were stapled onto the drywall later, coming out of a hole from the drywall (patched with joint compound). But it would be very difficult to hide all of it.
5 - I agree, that would pre-empt any question
6 - I was wondering about that, maybe unneccesary, but I saw mention of some type of spring hinge which would just replace the top hinge, on one site, no need for a "closer".
7 - I just read somewhere that concrete "backerboard" may be used at the lowest level (I guess they mean wonderboard?) if it can be cut or split. Just where it would touch the ground. This would be on the house side only, as I need to build a PT studwall down a couple feet, as on that side the house 1st floor is raised a bit and there is a gap where you can now see from that side of the garage into the crawlspace under the house. (It's all on piers as it's built on a steep mountainside).
8 - I sort of gathered that, just wanted to be sure, as it differs from interior work a bit (usually vertical)
9 - OK on that, but they'd be ok with what I choose then? even just R-13 not the maxxed out R-30 stuff, etc., no real poking around for it, since it would be covered up anyway.

Well, your info seems to be spot on, I pretty much have a plan together now, any refinements based on what I've just mentioned would be cool, before my trip to the lumberyard.
Have a great week...

I'm not sure if the wiring will cause a problem with inspection.

I don't use my real name because of the Google thing. I've got kids and have to keep some stuff private.

See where shameless self-promotion will get you?
Thanks for the mention though, and you're welcome to browse around my little homepage any time.
Tom in KY

Sounds like you folks got all the answers....I'm going back on vacation now....just stopped in ...
Square Eye....Love the google vid.

Classics die hard.