Thread: OSB walls in garage

Inspected a Townhouse today. New Construction. Three stories with the garage on the bottom story. Within the garage, there were sheetrock walls and two OSB walls above the block foundation wall on either side of the garage. Isn't this a fire hazard or because it is above the block foundation wall, it is suitable?

Also, are there any quidelines as to how far a hand rail is mounted to a stair wall. The distance was 1 1/4" from inside the railing to the wall. At one point the wall bowed in making it impossible to get your fingers around the hand rail unless you were a child. A woman wearing rings would certainly scratch the entire sheetrock wall going up or down.

Thanks,

Jim Murphy

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Originally Posted by JIM MURPHY

Inspected a Townhouse today. New Construction. Three stories with the garage on the bottom story. Within the garage, there were sheetrock walls and two OSB walls above the block foundation wall on either side of the garage. Isn't this a fire hazard or because it is above the block foundation wall, it is suitable? Also, are there any quidelines as to how far a hand rail is mounted to a stair wall. The distance was 1 1/4" from inside the railing to the wall. At one point the wall bowed in making it impossible to get your fingers around the hand rail unless you were a child. A woman wearing rings would certainly scratch the entire sheetrock wall going up or down. Thanks, Jim Murphy

Jim,

If these walls support the rooms above, they should be rocked.

I remember 1 1/2 inches between the inside of the handrail and the wall, but I don't have any documentation on that. .

The wood part of the handrail must be no closer than 1 1/2" from the wall. The grippable part of the handrail must fall in between 1 1/4" to 2". It can not stick out more than 4 1/2 from the wall into the stairway.

Originally Posted by Scott Patterson

The wood part of the handrail must be no closer than 1 1/2" from the wall.

To clarify what Scott said, you should be able to slide a 2x4 (1-1/2") between the handrail and the wall, from top to bottom.

The grippable part of the handrail must fall in between 1 1/4" to 2".

Referring to "diameter" with regard to circular handrails. Handrails which are not circular shall have a perimeter of at least 4" but not greater than 6-1/4" (for Type I handrails).

The handrail in the photo is not circular, thus the 1-1/4" to 2" does not apply to it, the perimeter limitations do.

This is the best way I have found to measure the perimeter of those handrails (and most come out to exceed the maximum 6-1/4" by-just-the-teensiest-bit, and are therefore not acceptable): take a piece of string, tape (use painters tape or something which will not leave a residue) wrap the string around the handrail, poking it tightly into all recesses, taping it in place along the way on the main surfaces (the style in the photo, tape it on top, wrap around one side, tape on the bottom, wrap around the other side, tape on top again) leaving a space on top to mark the string where the string wraps around to the first end of the string. Once you have it marked good and as accurately as possible, remove the tape, lay the string out straight, and measure between the two marks. The two marks are required to be at least 4" apart, but not any more than 6-1/4" apart. You will likely find the marks to be approximately 6-3/16", or maybe even 6-5/32", but that does not matter, what matters is that the marks *are greater than* 6-1/4" apart.

I had a builder tell his stair company the above, the stair company swore that the handrails were less than 6-1/4" in perimeter. I told the builder to get a letter from the handrail manufacturer stating that the perimeter of the handrails was less than 6-1/4" and have it signed and seal by their engineer ... their response back was ... yes, it was just a little bit over 6-1/4" in perimeter. The builder changed to circular handrails.

Type II handrails of other-than-circular cross-section are also allowed, provided them meet a more complex configuration. Even with the other-than-circular cross-section handrails, the graspable part above the finger grip must be no less than 1-1/4" wide and no greater than 2-3/4" wide.

Originally Posted by Gunnar Alquist

If these walls support the rooms above, they should be rocked.

Gunnar,

Looks like the gypsum board 'goes over' the top plate of that wall.

If it does, then the wall is not load bearing.

If any of those walls *are* loading bearing, then yes, they should have 1/2" gypsum board on them.

Of course, though, nothing stops the OSB from being applied first, or after, the gypsum board.

Originally Posted by Jerry Peck

Gunnar, Looks like the gypsum board 'goes over' the top plate of that wall. If it does, then the wall is not load bearing.

JP,

I would not want to make that assessment from these pics. Of course, I can see that you didn't either.

In my area, the walls and ceilings of an attached garage that abut the living structure are to be firewalled with a fire rated drywall. Are the walls with the OSB a shared wall with the living area?

Originally Posted by Mike Tracy

In my area, the walls and ceilings of an attached garage that abut the living structure are to be firewalled with a fire rated drywall.

Mike,

You need to be careful about using the term "firewall", or even your term "firewalled" in that unless it is a properly designed wall, i.e., a "fire-rated wall assembly" all that is being done is covering the wall with a Type X rated gypsum board on the garage side, which does not in any way make that wall a "firewall", or "fire-rated assembly" or even "firewalled".

It does raise the level of "separation", which is why the code states "separation".

Originally Posted by Richard Pultar

the AHJ is the final say..

While that is true, I know that many, many, many, home inspectors influence what the AHJ says.

Make friends at your local building departments, meet the inspectors and building officials, ask questions and learn, and, in doing so, you will be bringing things to their attention that they have not seen and the inspectors are not catching - things will slowly change ... for the better.

It really does work that way. It is good for both the home inspector and for the building department.

About 10 years ago I was at an educational seminar with about 500 inspectors, building officials, and contractors in the room, when the presiding speaker made a jerk comment about 'those jerk head home inspectors' who are always bringing things up against builders at new construction inspections (I don't remember exactly what term he used, but that is close enough) ... and I knew him and all of the speakers, he and the speakers all knew me too ... so I stood up, raised my hand, he called on me, and I said "I am one of those jerk head home inspectors, I am here to learn just like all of these other inspectors, building officials and contractors, and YOU KNOW ME and that I am always asking you questions, which you frequently take my side on, and not only am I here, gut (point to the others sitting around me) there are 11 other home inspectors sitting right here learning the same things all the inspectors and contractors are supposed to be learning - would you kindly teach them what you teach me" ... or wording something to that affect.

He stopped, hesitated, then turned to everyone and said 'Yes, there are MANY home inspectors who come to us and ask us questions, and, yes, they are right sometimes, not all home inspectors do not know what they are doing, some, like all those sitting there, want to learn like the rest of us.

How sweet it was to be able to nail him down in front of everyone like that. After that, I never heard him say anything about 'those jerk head home inspectors' again.

Jerry,

You are one hundred percent correct. I did mis speak there. It is a separation with the X rated drywall.

Thanks,

Mike

The OSB walls may be part of the wind bracing. It may be a shear wall.

Originally Posted by Wayne Carlisle

The OSB walls may be part of the wind bracing. It may be a shear wall.

Wayne,

Could be, but that would be one hookin' long shear wall if it were. What is it trying to resist - an F-5 tornado? I had not thought about it being a shear wall, but still ... that long?

Besides, that wall does not look anchored to the roof framing at the top, it looks like the gypsum board goes over top of the wall. Yes, it could be a shear wall without being anchored at the top, but a shear wall would be much stronger anchored top and bottom.

After going back and looking at the pictures again it appears that the structure is built in the floodplain and that the block walls are there for flood proofing and that in case of flooding the lower wall area will allow water to pass through and keek the damage minimal. What do they call those????? Blow out walls???? The OSB maybe part of that system. Just throwing out thoughts here!

Wayne,

Blowout walls, breakaway walls and frangible walls.

Blowout walls and breakaway walls are typically intended to break free (blowout) but remain attached at the foundation so the walls themselves do not become debris.

A frangible wall basically is made to come apart, but that would result in additional debris either floating around or blowing around.

They are all designed to help save the structure by reducing the wall loading in the flooded/moving water/wave action level. Flooding does not require breakaway walls, moving water and wave action does. Flooding just requires flood vents to allow the flood water outside the foundation walls to flow through and fill the inside area to the same depth, or to within 1 foot of the same depth, resulting in no more than 1 foot of water pressure difference on the foundation wall.

double studs,treated steps, posters location Daniel Island, sc it starts filling in the blanks

Originally Posted by Jerry Peck

Gunnar,

Looks like the gypsum board 'goes over' the top plate of that wall.

If it does, then the wall is not load bearing.

If any of those walls *are* loading bearing, then yes, they should have 1/2" gypsum board on them.

Of course, though, nothing stops the OSB from being applied first, or after, the gypsum board.

Jerry, do you have a where I can find this in UBC or IRC?

Originally Posted by Marc M

Jerry, do you have a where I can find this in UBC or IRC?

Marc,

I believe you are asking about where the code says to protect the walls and structure which supports the living space (which is what I was referring to).

From the 2006 IRC. (bold and underlining are mine)
- R309.2 Separation required. The garage shall be separated from the residence and its attic area by not less than 1/2-inch (12.7 mm) gypsum board applied to the garage side. Garages beneath habitable rooms shall be separated from all habitable rooms above by not less than 5/8-inch (15.9 mm) Type X gypsum board or equivalent. Where the separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than 1/2-inch (12.7 mm) gypsum board or equivalent. Garages located less than 3 feet (914 mm) from a dwelling unit on the same lot shall be protected with not less than 1/2-inch (12.7 mm) gypsum board applied to the interior side of exterior walls that are within this area. Openings in these walls shall be regulated by Section R309.1. This provision does not apply to garage walls that are perpendicular to the adjacent dwelling unit wall.

Hard to tell from the photo, but the 2nd pic appears to show the OSB resting on the block wall. Being the OSB is not pressure treated, shouldn't there be a gap separating the bottom of the OSB from the wall?

Originally Posted by Jerry Peck

Marc,

I believe you are asking about where the code says to protect the walls and structure which supports the living space (which is what I was referring to).

From the 2006 IRC. (bold and underlining are mine)
- R309.2 Separation required. The garage shall be separated from the residence and its attic area by not less than 1/2-inch (12.7 mm) gypsum board applied to the garage side. Garages beneath habitable rooms shall be separated from all habitable rooms above by not less than 5/8-inch (15.9 mm) Type X gypsum board or equivalent. Where the separation is a floor-ceiling assembly, the structure supporting the separation shall also be protected by not less than 1/2-inch (12.7 mm) gypsum board or equivalent. Garages located less than 3 feet (914 mm) from a dwelling unit on the same lot shall be protected with not less than 1/2-inch (12.7 mm) gypsum board applied to the interior side of exterior walls that are within this area. Openings in these walls shall be regulated by Section R309.1. This provision does not apply to garage walls that are perpendicular to the adjacent dwelling unit wall.

Hey Jerry, I knew of that one. I thought there was something i was missing. Thanks.

What about for a commercial garage? I run an auto shop and would like to remove the ancient drywall and put up 1/2" OSB in place of that. The garage is not attached to anything, it is free standing. Any issues?

Originally Posted by Mario Grozdanovski

What about for a commercial garage? I run an auto shop and would like to remove the ancient drywall and put up 1/2" OSB in place of that. The garage is not attached to anything, it is free standing. Any issues?

Fire safety

It is a match box with a match in hand waiting to be struck. Putting OSB on the drywall then you still have a firewall behind it. Office separation from the garage?

Anyway, you will have to check with the city and local fire department.

Last year I inspected a commercial garage. The office area next to the garage had no protection (some 1/2 drywall on the inside and plywood on the garage side. Worse than that there were stairs in the middle of that office area than ran up from the garage to offices above and no door at the top and it was the only way out. No ventilation at all so the office folks sucked fumes all day. I could go on about that place for the 2 hours it took for the report.

Do you think that passed?