8'-0" max spacing perpendicular to deck slope
8'-0" max spacing perpendicular to deck slope
(OP)
I have an attic space that is currently protected by BB attic sprinklers and AP sprinklers, it was an unoccupied attic area. Roof pitch is around 12/12.. They are going to occupy this space with offices and install a wood plank ceiling directly onto the roof structure so no roof joist will be exposed. It will not really be a "concealed space" at this point. There will be exposed wood truss's beams going across the space spaced 8'-0" on center +-.. They are proposing to remove the ATTIC sprinklers since it will be an occupied space, and want to install standard uprights for the new occupancy.
Per 2010 Nfpa 13, 8.6.2.2.1 (A) it says: For combustible concealed space under a pitched roof having combustible wood joist or combustible truss construction with members less than 3'-0" on center with slopes greater than 4 in 12 pitch. To the right under the Max Spacing column it says: 15'-0" parallel to the slope 10'-0" perpendicular to the slope, with an asterisk * that refers to 8.6.2.2.1.1 which says when 8 foot max spacing perpendicular to the roof slope is exceeded the minimum pressure shall be 20 psi...
Since this space will no longer be considered a concealed space, does the 8'-0" max spacing perpendicular to the roof slope rule still apply because of the roof pitch?
Does that rule apply to an occupied space in addition to combustible concealed spaces ?
I know I need to increase the remote area for the roof pitch, but 8'-0" max spacing will really kill the job as I will end up calculating the entire space, and it will not work most likely.
Thanks in advance.
Per 2010 Nfpa 13, 8.6.2.2.1 (A) it says: For combustible concealed space under a pitched roof having combustible wood joist or combustible truss construction with members less than 3'-0" on center with slopes greater than 4 in 12 pitch. To the right under the Max Spacing column it says: 15'-0" parallel to the slope 10'-0" perpendicular to the slope, with an asterisk * that refers to 8.6.2.2.1.1 which says when 8 foot max spacing perpendicular to the roof slope is exceeded the minimum pressure shall be 20 psi...
Since this space will no longer be considered a concealed space, does the 8'-0" max spacing perpendicular to the roof slope rule still apply because of the roof pitch?
Does that rule apply to an occupied space in addition to combustible concealed spaces ?
I know I need to increase the remote area for the roof pitch, but 8'-0" max spacing will really kill the job as I will end up calculating the entire space, and it will not work most likely.
Thanks in advance.





RE: 8'-0" max spacing perpendicular to deck slope
1 - If the space is occupied, it should be conditioned. At that point, you can use 4.2k sprinklers and a wet system. That will drastically cut down on the over-discharge.
2 - I would say that you no longer have a concealed space and the concealed spaces requirements are not applicable.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...
RE: 8'-0" max spacing perpendicular to deck slope
RE: 8'-0" max spacing perpendicular to deck slope
RE: 8'-0" max spacing perpendicular to deck slope
Since you "space on the slope and calc on the flat," you may even want to look at 2.8k sprinklers as that area per sprinkler on the flat projection is going to be pretty small. That is provided you have a wet pipe system.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...
RE: 8'-0" max spacing perpendicular to deck slope
Are you sure about the 130 sq. ft spacing? If it falls under Combustible unobstructed with exposed members more than 3'-0" O.C (The exposed beams/ trusses) 8.6.2.2.1 says I can go to 225 sq.ft spacing with a calculated system.
It's 18'-4" to the peak.. Would I still be allowed a slight reduction in my remote area for qr sprinklers if I have to initially increase it by 30% for the steep pitch deck?
Thanks guys!
RE: 8'-0" max spacing perpendicular to deck slope
Yes, you can apply multiple reductions. At 18.333', you would be 1438 sq ft design area.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...
RE: 8'-0" max spacing perpendicular to deck slope
RE: 8'-0" max spacing perpendicular to deck slope
The collar ties do not make this space "obstructed construction" but would these collar ties put the sprinkler spacing under the category of Combustible unobstructed with exposed members less than 3'-0" on center? for a max spacing of 130 sq.ft per sprinkler? This seems like it would, but I am just trying to be sure before I move ahead with my layout.
Sorry for any confusion.
Thanks for your help
RE: 8'-0" max spacing perpendicular to deck slope
Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...
RE: 8'-0" max spacing perpendicular to deck slope
Thanks for all your help.
RE: 8'-0" max spacing perpendicular to deck slope
RE: 8'-0" max spacing perpendicular to deck slope
Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...
RE: 8'-0" max spacing perpendicular to deck slope
Thanks
RE: 8'-0" max spacing perpendicular to deck slope
Q=k*P^.5
Once you know your Q, you can then divide by your density to get the spacing that corresponds to the Q.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...