TO TEAR OR NOT TO TEAR

[guillermo]

I need to add several outlets to an existing fire rated wall, the general contractor wants to remove all the drywall to do the job, there is more than 3,000 s.f. of drywall to be removed. Question, can the contractor cut a strip of drywall so that the new outlets can be added and patch the wall instead of removing the entire wall? This would save a lot of time, material and labor. This is for the tenant improvements on a commercial building. Thanks for your help.

 

[readydave8]

I need to add several outlets to an existing fire rated wall, the general contractor wants to remove all the drywall to do the job, there is more than 3,000 s.f. of drywall to be removed. Question, can the contractor cut a strip of drywall so that the new outlets can be added and patch the wall instead of removing the entire wall? This would save a lot of time, material and labor. This is for the tenant improvements on a commercial building. Thanks for your help.

yes

 

[Ponchik]

why would the general want to remove the whole wall anyway? Extra labor and and more $$$$ :happyyes:

Assuming it is T bar, can't you do your wiring above and drop your conduit or MC/AC through the wall?

 

[kwired]

Does GC have more in mind than just removal for the electrical installation?

 

[iwire]

I need to add several outlets to an existing fire rated wall, the general contractor wants to remove all the drywall to do the job, there is more than 3,000 s.f. of drywall to be removed. Question, can the contractor cut a strip of drywall so that the new outlets can be added and patch the wall instead of removing the entire wall? This would save a lot of time, material and labor. This is for the tenant improvements on a commercial building. Thanks for your help.

Couple of points.

1) If it is a fire rated wall you can't use old works, you must attach any boxes to the studs.

2) If it is a fire rated wall with two layers, if they where to patch it up they would have to stagger the joints. So if you cut a strip you would have to cut the top layer much wider than the bottom layer which kind of sucks to do. You also end up with a patch that is hard to blend.

 

[JDB3]

Joe

Joe

As to the patching, I have seen sheet rock patch jobs, where I have known exactly where it was done, but yet I could not detect any signs of a patch "at all". So the patch just depends upon the skill level, just like in electrical trade.:happyyes:

 

[Microwatt]

Couple of points.

1) If it is a fire rated wall you can't use old works, you must attach any boxes to the studs.

IWIRE,

I would like to know more on this. I don't recall anything about this in the NEC. Does it come from the IBC?

 

[iwire]

IWIRE,

I would like to know more on this. I don't recall anything about this in the NEC. Does it come from the IBC?

It is in the UL Orange book which describes how a fire rated assembly has to be constructed so a building official could fail you for using old works.

 

[iwire]

As to the patching, I have seen sheet rock patch jobs, where I have known exactly where it was done, but yet I could not detect any signs of a patch "at all". So the patch just depends upon the skill level, just like in electrical trade.:happyyes:

Uh huh.

 

[cowboyjwc]

Couple of points.

1) If it is a fire rated wall you can't use old works, you must attach any boxes to the studs.

2) If it is a fire rated wall with two layers, if they where to patch it up they would have to stagger the joints. So if you cut a strip you would have to cut the top layer much wider than the bottom layer which kind of sucks to do. You also end up with a patch that is hard to blend.

Bob stole my answer.

The two layers is the hardest one to patch. Even if it's only one layer, you have to go stud to stud to patch it. Tape joints have to be on a stud, except for the horizontal ones.

Also if you are adding receptacles to an existing fire wall you need to check the other side, to make sure that you either stagger your boxes or put fire pads on both boxes.

 

[renosteinke]

One does need to know more ... much more ... to get the 'right' answer.

The UL "Orange Books" are but one source of fire rated assemblies. There are others - the "Gypsum Handbook" put out by USG is one - but the point is that walls are rated as complete assemblies.

There's also the little detail that the 'rating' refers to temperatures developed on the unexposed face during the test. What this means is that it is possible for the wall to be built in such a way that ALL of the 'fire rating' depends upon one face alone. The other face isn't necessary for the rating, and ordinary methods may be used.

What this means is that you must know exactly what rating is required, and what the exact assembly is.

There are very, very few general 'rules of thumb' that you can trust. Your job specifications need to address this issue.

Your governing code would be the building code.

 

[Strathead]

To Expound on Renosteinke

To Expound on Renosteinke

One does need to know more ... much more ... to get the 'right' answer.

The UL "Orange Books" are but one source of fire rated assemblies. There are others - the "Gypsum Handbook" put out by USG is one - but the point is that walls are rated as complete assemblies.

There's also the little detail that the 'rating' refers to temperatures developed on the unexposed face during the test. What this means is that it is possible for the wall to be built in such a way that ALL of the 'fire rating' depends upon one face alone. The other face isn't necessary for the rating, and ordinary methods may be used.

What this means is that you must know exactly what rating is required, and what the exact assembly is.

There are very, very few general 'rules of thumb' that you can trust. Your job specifications need to address this issue.

Your governing code would be the building code.

There is also the poetential listing available for products from the manufacturer. "Fire rated" alone means very little. And just because a wall has 2 layers of sheetrock does not mean it is fire rated. Just because a wall was fire rated doesn't mean it still is! Assuming it is though the first issue is what fire rating?

 

[Strathead]

Couple of points.

1) If it is a fire rated wall you can't use old works, you must attach any boxes to the studs.

2) If it is a fire rated wall with two layers, if they where to patch it up they would have to stagger the joints. So if you cut a strip you would have to cut the top layer much wider than the bottom layer which kind of sucks to do. You also end up with a patch that is hard to blend.

Huh? Metal boxes are listed for 2 hour fire rating. Nothing about being attached to studs. I have used them hundreds of times in 1 hour fire walls.

 

[raider1]

Huh? Metal boxes are listed for 2 hour fire rating. Nothing about being attached to studs. I have used them hundreds of times in 1 hour fire walls.

For a metal box to be installed in a fire rated wall the box must be securely fastened to the framing member.

Here is a quote from Thomas and Betts dealing with Steel city boxes.

"The metallic outlet or switch boxes shall be securely fastened to the studs and the opening in the wallboard facing shall be cut
so that the clearance between the box and the wallboard does not exceed a in."

HERE is a link to the PDF.

Chris

 

[cowboyjwc]

There is also the poetential listing available for products from the manufacturer. "Fire rated" alone means very little. And just because a wall has 2 layers of sheetrock does not mean it is fire rated. Just because a wall was fire rated doesn't mean it still is! Assuming it is though the first issue is what fire rating?

I wouldn't argue with that, but I wouldn't hang my hat on it either. As an inspector if it walks like a duck and quacks like a duck...... A good indication that it's a rated wall is if it's taped above the t-bar line. Also it could be an area seperation wall that was put in years ago to get around the requirement for fire sprinklers. Just because it's a B to a B doesn't mean it's not a rated wall.

Now to agree with you a little, a sound wall and a rated wall look much alike.

 

[sandsnow]

You do not want the book from USG (a manufacturer), you want the Gypsum Association Book.

Metal boxes are NOT listed for 2 hours. They are permitted as part of a fire resistive wall as stated in the UL guide Info for fire resistive construction. There are conditions.

Repair of fire resistive assemblies (read carefully, multi layer is addressed): http://www.gypsum.org/pdf/225-08.pdf

 

[guillermo]

Does GC have more in mind than just removal for the electrical installation?

Nope, the removal is due to the installation of more outlets and nothing more

 

[guillermo]

I wouldn't argue with that, but I wouldn't hang my hat on it either. As an inspector if it walks like a duck and quacks like a duck...... A good indication that it's a rated wall is if it's taped above the t-bar line. Also it could be an area seperation wall that was put in years ago to get around the requirement for fire sprinklers. Just because it's a B to a B doesn't mean it's not a rated wall.

Now to agree with you a little, a sound wall and a rated wall look much alike.

Mike,

two walls separate the suite from a main access corridor, the other two walls face the exterior. The wall is sealed from top to bottom and the building has fire sprinklers, there are no electrical boxes on the other side.

 

[cowboyjwc]

Mike,

two walls separate the suite from a main access corridor, the other two walls face the exterior. The wall is sealed from top to bottom and the building has fire sprinklers, there are no electrical boxes on the other side.

Or you could know that it's a rated wall. :happyyes:

 

[petersonra]

Nope, the removal is due to the installation of more outlets and nothing more

It seems to me this is not an electrical issue. I would let the GC decide how he wants to handle drywall issues.