Garage separation question

[Sifu]

May have been covered before but a quick search didn't yield any answers. I have read codes and commentaries and want to see what you folks think and enforce.

R302.6 and table 302.6. Requires 1/2" on supporting structures where supporting "floor/ceiling" assemblies. If you have a wall supporting trusses but it is attic space only, no habitable space above, does that wall require 1/2" drywall? Same question with a beam. Beam is protected but the column is not. The beam supports the trusses mid-span but only has an attic above. The attic has no access other than a 22x30 hatch.

To me if it is a floor-habitable space above, the wall protection is definately required. Not so sure about a ceiling though.

 

[steveray]

I would have to look at the newer code....Here it is still 5/8"...either abutting wall to the roof deck or 360 degrees in the garage....You could make an arguement for a nonbearing wall, but noone has yet....

 

[fatboy]

Same as steveray.....5/8". We require that any wall, beam or column that is supporting the required separation to be rocked.

 

[mtlogcabin]

To me if it is a floor-habitable space above, the wall protection is definitely required. Yes I agree



Not so sure about a ceiling though. Good thought provoking question.

Table R302.6

Structure(s) supporting floor/ceiling assemblies used for separation required by this section

I think the answer is in "floor/ceiling" this would require protection of a single assembly

A ceiling assembly is not required to have the supporting walls protected

 

[Mac]

NY wants the 'supporting structure' protected also...

R309.2.1 Vertical separations. Where partitions are used to separate an attached garage from a living space or its attic, the partition assembly shall have a 3/4-hour fire-resistance rating.

Exception: In lieu of providing partitions that have a 3/4-hour fire-resistance rating, one layer of 5/8-inch thick, type-X, gypsum board may be installed on the garage side and one layer of 1/2-inch, type X, gypsum board may be installed on the opposite side. Application shall be in accordance with Section R702.3.

R309.2.2 Horizontal separations. Where horizontal construction is used to separate the garage from the living space or its attic, such construction shall be protected with one layer of 5/8-inch thick, type X, gypsum board, installed in accordance with the requirements of Section 805.1. Openings in horizontal separations shall not be permitted except where the residence is otherwise protected by vertical separations. Where the horizontal separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than 5/8-inch (15.87 mm) type X gypsum board or equivalent.

 

[Builder Bob]

Just a quick note, the 22x30 hatch eliminates the protection afforded by the gypsum in place......I don't believe the trim attached around the perimeter of the hatch provided 15 minute thermal protection like the 1/2 Inch sheet rock at 1200 degrees Fahrenheit. Pine has a char rate of 1 1/2" per hour........ so the trim's minimum thickness would have to be 3/8" thick to provide the same level of protection as the 1/2" sheet rock.

 

[Sifu]

BB, The hatch is built a little differently. They line the framing inside with a layer of 5/8 X, then lay a panel on top of the lip that the lining creates. We require the panel to be two layer of 5/8 x laminated to give it added weight, mostly they tape and mud it in place. Basically it creates an inset in the framing that the lid sits on. Don't know if that changes your thought on the hatch eliminating the protection.

I personally like the supporting walls to be protected........but what I like is not important. What I can back up with code is. I see most are in the same frame of mind as me but I don't think the code supports me on this.

 

[steveray]

The intent is.....if the walls fall down, what good does the ceiling do.....anything supporting the seperation needs to last as long as the seperation...

 

[fatboy]

Bingo steveray..........

 

[Sifu]

The way it has been explained is that the intent is to prevent or delay the communication of fire or smoke with the areas above without the building occupants being aware of it, and if the fire or smoke can only make it to the area above if the wall collapses the occupants would certainly know about it. Not to say I don't agree with you, just explaining the intent as it has been explained to me. I do understand that intent based on the premis that we aren't trying to prevent the building from burning, we are only trying to prevent the building from burning with the occupants inside of it. Basically my boss is saying the wall does not need protection because of this argument after I wrote a correction on it. I am trying to present my argument but I am not sure the code actually supports me after I hear his interpretation of the intent. Everything I have read continually says "floor" or "Habitable space" or "floor/ceiling assembly", none of which appear to be the condition I am describing.

 

[fatboy]

To each his own. We have enforced it for many years in the manner I described........floor/ceiling could also be taken as floor and/or ceiling assemblies.

 

[mtlogcabin]

The intent is to keep fire out of the attic above the living space

The protection is required at the garage wall line on the garage side of the wall.

Maybe the question should be is 1/2" gypsum board permitted on the garage ceiling in lieu of the garage wall location requirement?

1/2" gypsum board gives you about 15 minutes when install on 2 X 4 studs at 16" OC.

How much time does 1/2" gypsum board have when installed on trusses at 24" OC?

 

[mark handler]

Heat rises it takes less time to burn though the lid than the value walls, therfore the lid material needs to be thicker.

We have had this conversation before

 

[mtlogcabin]

therfore the lid material needs to be thicker.

I agree but the code only requires 1/2"

 

[mark handler]

when living space is above?

 

[fatboy]

"Heat rises it takes less time to burn though the lid than the value walls, therfore the lid material needs to be thicker.

We have had this conversation before"

And with probably the same result.............

 

[mtlogcabin]

The OP was not talking about a living space above. Hence the IRC only requires 1/2" on a ceiling in a garage when no living space above. Hard to find 1/2" for ceilings with 24" OC truss spacing but they do make it.

As for the 5/8" requirement for gypsum on a garage ceiling with a living space above don't forget to tighten up the fastener spacing to I believe it is 8" in the field.

 

[Sifu]

Like Fatboy said, to each his own. The OP was whether or not the code required 1/2" on the wall supporting trusses with no living space above (for example, the outer garage wall-not the common wall). The code and commentary contains language that seems to indicate that it is only required when a living or habitable space is above by using the term "floor/ceiling assemby". Any other time I have seen this term I have understood it ot be a floor and a ceiling. Therefore I wonder about the true intent. I want to require the drywall like most of you but because of the language I am unable to convince my boss. I was looking for some hard evidence but as usual the grey area is bigger than the black and white.

 

[mtlogcabin]

I want to require the drywall

Why?

If there is no living space above what are you tying to achieve by requiring drywall on a garage wall just because drywall has have been installed on the bottom of the trusses thereby creating a ceiling?

You start doing this and a savvy builder will realize he can install drywall on the garage side of the garage wall from floor to roof deck cheaper than what you "want" and you will loose all the drywall on the garage walls and ceiling

Your BO does not need to be convinced, He needs to be shown a specific code section and what you are wanting is just not there in the IRC.

 

[JBI]

The garage needs to be completely separated from the dwelling.

Option 1 - Run the common wall GWB up to the underside of the roof deck.

Option 2 - Complete the separation using the walls and ceiling of the garage.

For the access opening in the ceiling, they do make rated pull down stairs for use in rated ceiling assemblies (and no, I don't want to go through the 'attic stair' thread again! )

 

[Sifu]

Your BO does not need to be convinced, He needs to be shown a specific code section and what you are wanting is just not there in the IRC.

I agree, thats the point of this thread, that is to say I can't find the code to support it either. I guess I should re-phrase the I want part. Better to say I have thought/assumed that the intent was to require it. Once I looked at it, after my boss questioned it I found my assumption is likely wrong. I just looked at the 06,09,12 commentaries and they all seem to say the same thing; "additionally, the exterior walls of the garage are required to have 1/2" gypsum board on the interior face where they support floors separating all or part of a dwelling unit above the garage". Now that I have read them all again I'm not sure why I didn't see it as well before. Oh well, at least this thread made me figure something out.