10.2.7.2.1.3* Minimum Distance from Obstructions and the 3 Times Rule

[SprinklerDesigner2]

What we see here is just part of a 10,000 sq ft floor space and what we see in the photo below is the finished product. Even the offices you see on the top photo has the exposed wood joists.

Construction was completed two years ago so what you see is what you get as an end product.

If we had drywall ceilings life would be easy with interstitial sprinklers but this isn't the case.

It isn't all office so the design will be per OH-1.

10.2.7.2.1.3* Minimum Distance from Obstructions.
Unless the requirements of 10.2.7.2.1.4 through 10.2.7.2.1.9 are met, sprinklers shall be positioned away from obstructions a minimum distance of three times the maximum dimension of the obstruction (e.g., structural members, pipe, columns, and fixtures) in accordance with Figure 10.2.7.2.1.3(a) and Figure 10.2.7.2.1.3(b).
(A) The maximum clear distance required shall be 24 in. (600 mm).
(B) The maximum clear distance shall not be applied to obstructions in the vertical
orientation (e.g., columns).

As you can see we're dealing with 2x4 members where the 4" is actually 3 1/2" so with the 3 times rule I have to be 10 1/2" away from the diagonal members which poses a problem with joists 16" OC,

But my can I ignore the vertical truss members in laying the heads out? I think I can but while trusses like these are not unusual having them exposed with Ordinary Hazard Occupancy for me is. Life would be easier if they were 24" OC but they aren't.

There not columns but what's the difference?

The owner wants the piping above the bottom of the joists which means even more fun.

The building is actually three stories with the second floor equipped with a drywall ceiling. I will use interstitial sprinklers between the second and third floor but to get at it the owner wants to temporarily take up the third 4x8 plywood decking.

 

[TravisMack]

Are they open enough to not be obstructed construction?

Travis Mack, SET, RME-G,
Ferguson Fire & Fab, dba MFP Design

http://www.mfpdesign.com

 

[SprinklerDesigner2]

Now I am not sure it can even be done.

I don't remember ever having exposed open wood trusses that were less than 24 inches on center.

 

[LittleInch]

Looks fairly obstructed to me.

But why can't you just run pipes right along the underside of the joists? Or on top of the joists and drop sprinklers down to just below the bottom of the bottom joist?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SprinklerDesigner2]

The joists are 24" deep.