Kyle,
I'm taking a first stab at addressing this, and basing my replies and
section references on the 2016 edition of -13. Here goes:
* You're correct in establishing that wood trusses as you've
described, with top and bottom chord members of greater than 4" in
depth, as obstructed construction based on the definitions and annex
material in §3.7.1, and §A.3.7.1(9), and Figure A.3.7.1(c).
In that respect the deflectors of the upright sprinklers would have
to be no more than 22" down from the deck above, and between 1"-6"
below the bottom of the truss. So the first question for me - are
they deeper than 22"?
If not, there would be no need to locate the sprinklers above the
bottom chord, provided the 1"-6" could be met.
* With respect to the insulation, §8.5.4.1.3 would suggest that if the
space between the trusses were were filled to the underside of the
ceiling with insulation, then the deflector distance is to be
measured to the underside of the insulation. there are some
examples in the handbook for insulation which sags, however that's
for another discussion.
I hope that helps you.
sincerely,
*Ken Wagoner, SET*
*Parsley Consulting
500 West Mechanic Street
Harrisonville, Missouri 64701-2235*
*Phone: (760) 745-6181 *
*Visit the website
<https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.parsleyconsulting.com%2f&c=E,1,Y5zKJKPEh1mBEBqSR-VE9cUKl5y-eyP8BpvmE_5j9ZqW2eJbNphYzrCMBZ-2YuX6d-RRkHI4gQ1FV-cvOeCfRC58uZS9NiToZv2mx7909oCqLvCW_n5hDHeK&typo=1>*
On 7/19/2022 11:56 AM, Kyle.Montgomery wrote:
I have a project with wood truss structure (top and bottom members are
greater than 4”), which classifies it as obstructed construction. The
trusses are 24” on center and all the members are at lease 2x4s, so it
really would be just about impossible to put sprinklers up in the
truss space without them being pretty badly obstructed (I don’t think
we could satisfy the 3x rule).
My question is, does the insulation matter? It’s actually a 2-part
question:
1. The insulation depth will probably completely cover the top chord
member. Is it still obstructed construction if there is
essentially no top member below the insulation?
2. If the answer to number 1 is “yes”, then would it matter if the
top chord was NOT greater than 4” since it would be covered by
insulation regardless?
-Kyle M
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