Sidewalls under Overhead doors

[skdesigner]

Mundane question for a thursday afternoon.

NFPA 13 2010 8.7.3.1.7 Permits sidewalls under overhead doors in an otherwise ordinary hazard area to be spaced for light hazard.

8.3.3.1 would dictate these sprinklers have quick response elements.

8.3.3.2 then requires that if the sidewalls are quick response, all sprinklers in the compartment shall be quick response.

So, if we're talking an OH2 pre-eng building with 30' AFF deck (i.e can't use QR to reduce the remote area), are the uprights now required to be QR because of 8.3.3.2?

I've always assumed that "protection area and maximum spacing for light hazard" is different than actually being a light hazard occupancy, but I like to second guess myself.

What says the forum?

 

[TravisMack]

I have always used SR sidewalls in this application. I just go with 14'x14' spacing for the sidewalls.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[skdesigner]

Thanks Travis, that's what I've always done too. A fitter actually asked the question today, and it made me think twice about it.

 

[NJ1]

I dont want to start any friction but my question has always being:

Why do you have to install sprinkler heads under a overhead door
since someone is most likely to be operating the door? Wouldn't that be the same as a fire watch?
What is the difference from not having sprinklers under such door vs having a system shut down with a fire watch.


If the door is up it means someone is there. Would you leave your space unattended like this? HELLO!

 

[fireguy519345]

I was watching a lift truck go in and out an open overhead door. All his trips and never once did he close the door. I have also seen the doors left open on a nice day. When I drove a lift truck, I often left the doors open. At that time, I did not even know there were fire sprinklers.

 

[skdesigner]

"Why do you have to install sprinkler heads under a overhead door"

Because that's what the book says.

Specifically, NFPA 13 2010 8.5.5.3.1 Sprinklers SHALL be installed under fixed obstructions over 4ft wide such as ducts, decks, open grate flooring, cutting tables and OVERHEAD DOORS.

 

[NJ1]

skdesigner


That was a very well answer question. A technical one at that.

 

[b1ueshift]

NJ1 & skdesigner I think you both have a case.

Skdesigner is thinking that you should follow the NFPA 13 standard as closely as possible, then not only will your design be safe, but you can easily demonstrate this safety to a third party (ie it complies with the standard therefore it is safe).

NJ1 is thinking you shouldn't follow a standard blindly. What if the standard told you to jump off a bridge for example? If you can see a way to save the building owner some money which has negligable effect on safety and you can persuade an AHJ to accept it, then why not?

For my 2 cents, if NPFA 13 specifically mentions that you should put sprinklers under overhead doors, then you should probably do it. Also don't be surprised if you get some flack over it especially if you work with people who don't believe in following standards.

 

[TyphoonK]

skdesigner, 8.7.3.1.7 permits sidewall to have the protection area and maximum spacing for LH, but the occupancy would still be OH. To justify, I would interpret that the density for OH would still apply to this sprinkler since only the area and spacing were permitted to be modified. Since the occupancy is still OH, 8.3.3.1 wouldn't apply.

just my novice interpretation.

 

[NJ1]

My whole point with the comment I made is that yes indeed the code is written for an specific reason and purpose how ever lets look at this very closely:
Yes indeed obstructions over 4' Wide need sprinkler protection underneath however these obstructions are not nor need to be monitor by anyone in many cases therefore protection must be provided.
As skdesigner mentioned:
"Specifically, NFPA 13 2010 8.5.5.3.1 Sprinklers SHALL be installed under fixed obstructions over 4ft wide such as ducts, decks, open grate flooring, cutting tables and OVERHEAD DOORS".

My point is that when an overhead door is open it means that someone opened it. You do not leave an overhead door open with building unattended. Do you?

I this this part of the code is overkilled.

 

[chillylulu]

NJ1

Doors are opened and left open often. I don't know where you are, but the crime rate must be high. Recently we modified systems at an occupied meat processing plant. Trucks back trailers up to the door and leave them. Then someone opens the door on the inside and they leave it open for hours. Other facilities do this to. A lot of garages leave the doors open to let the weather in. The tire place by my house opens all 6 or 8 doors and they leave them open most of the time. Doors are left open and unattended regularly.

The important part is that when they are opened, the hazard underneath is light - vehicles coming and going, usually nothing there. The amount of combustible material is likely minor under an open door. A closed door can stay closed and the area can and regularly does get used in a way similar to the rest of the space. So you still need the density above the doors the same as the rest of the hazard. Additionally, most sprinkler design is for control rather than extinguishment. A fire can be controlled by a lighter density under the door and a higher density flooding down all around the edges.

Spacing for light hazard is appropriate. Like Travis said, use SR heads bercause the occupancy is still ordinary hazard. The density doesn't usually matter because you don't have to calc them with the overhead sprinklers.

SK - I like the fact that your fitter asked you about this. He is either a keeper or trouble.

I'd like to ask a follow up. Since we have sidewalls under the door can a single drop down supply 2 doors next to each other? Do the heads have to be far enough away from each other to prevent cold soldering? The problem occurs when you have a row (3 or more) of doors that are > 14 feet wide and are only a couple of feet apart. You need heads on both sides, but both sides of the center door are too close to the heads at the door on either side. What would you do?

 

[Jondoeiowa]

Just thought I would add this onto this post. As we recently had to do work on an Extra Hazard building with overhead doors.