Language camp facility. Rural area. Installing a underground water storage tank 
with vertical turbine pump. Originally we were to provide partial sprinkling of 
just the dining hall not sure if that meant the attic above it or not. The Fire 
Marshal and others convinced them to provide complete sprinkler of two 
buildings (and more as the campus get built out.) the demand is driven by the 
kitchen in the dining hall. (BTW the fire marshal wants us to use one of those 
weird MN domestic water pump as a supply for the fire protection system.. 
Yuck.. no local driller can drill the required 10 inch well and the risk of not 
having enough water at the yearly test drove us to the tank)

The dining hall has a convoluted 4500 SF attic with some standard attic that is 
accessible, but that has a 6 foot wide flat roof section with skylights running 
down the middle.

Of that a 1000 SF area that has been created with scissor trusses and the 
skylights and flat area over a dining area.

There is a inaccessible dropped wood ceiling below the attic structure where we 
will run the wet system protecting the dining room. The gypsum above this could 
be marked for access points.

And yes, cut holes if needed for the inspection.

Writing the spec now, I have been using nitrogen for the last few system 
designs, I wasn't sure I should for this one due to cost as there is an 
adjoining building with a "normal" dry system for the attic and the 8 foot wide 
combustible eaves. Is a small nitrogen generator cost effective?

The problem with the insulation is the almost 48 inch depth required at the 
"thick" part of the scissor truss. This architect doesn't want to do it that 
way, although our housing group regularly designs flat truss roofs with near 30 
inch thick insulation due to past experience with burst/leaking sprinklers.

What about Ron's contention that no access should be provided.

I think you have convinced me to at least specify nitrogen and schedule 40 over 
the limited access area, with a prohibition on groove joint in those areas.

David T Williams - Lead MEP/FP Engineer


From: Scott Futrell <>
Sent: Thursday, August 15, 2019 2:08 PM
Cc: David Williams <>
Subject: RE: Attic/Concealed space access to sprinkler heads


Interesting question. You haven't provided enough information for a thorough 

How big of an attic area?

So you intend to mark the location of every upright sprinkler in the concealed 
space on the ceiling below? No one will ever paint that gypsum?

Then cut access for NFPA 25 5-year internal pipe inspection?

And cut access for NFPA 25 20-year sprinkler inspection?

Life expectancy of a design/build NFPA 13 dry sprinkler system, riser mounted 
air compressor, schedule 10, black steel pipe = 7-15 years.  Is that the system 
you are specifying?

Or, are you specifying with nitrogen and schedule 40 pipe?  Other?

Why not fill with insulation? As long as you avoid mold issues (see webinar) 
that could be a better long-term option for your current client and whoever 
buys it next.

NFPA 25 requires limited access for internal inspection, but if anything goes 
wrong (e.g. corrosion) how do you work on it without taking significant pieces 
of the ceiling down.

Can you imagine how hard it is to locate pipe and problems in that space (i.e. 
Confined space) without accurate as-built drawings (I'm lucky if the owner has 
any drawings, but as-built for those spaces aren't the norm). We've taken off 
the roof of structures less than two years old to locate pipe and abandoned dry 
systems in attics because it is too expensive to take the ceilings down just to 
start locating the leaks and facilitate repairs.

Too many questions for a simple answer.

It'll be great to hear other responses.


Office: (763) 425-1001 x 2
Cell: (612) 759-5556

From: Sprinklerforum 
 On Behalf Of David Williams via Sprinklerforum
Sent: Thursday, August 15, 2019 1:43 PM
Cc: David Williams 
Subject: Attic/Concealed space access to sprinkler heads

I have a project intended to be fully sprinkled with a combustible attic that 
tapers from 2' to 4 ' without being filled to within 2 inches of the deck with 
insulation. So I am planning on a dry pipe system with standard heads as the 
design of the attic does not allow the effective use of special application 
attic sprinklers.

The questions are: whether inspection access is required to be provided, is it 
prudent to do so at the heads, or can the locations just be noted on the gypsum 
mounted to the bottom chord of the open web trusses.


David T Williams, PE - Lead MEP/FP Engineer
21 West Superior Street, Suite 500, Duluth, MN 55802
Direct 218.279.2436 | Cell 218.310.2446<>


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