RTU on Deck
RTU on Deck
(OP)
We are installing a rooftop AC on an existing roof. We will be installing angle framework to support the unit and curb between joists which are 5' o.c. I intend to build the curb with treated wood either on top of the deck directly over the angle framework and build it up directly from the angle framework. Are there any guidelines as to when it is OK to build on top of the deck so the deck is not "squashed" between the curb and support frame? Maybe an allowable plf of curb perimeter? Most details I have seen show the curb on top of the deck. A Vulcraft deck manual was no help. An NRCA manual detail shows it both placed on the deck, and directly on the support "for heavy units". Deck is 22 ga Type B. The unit has not been specified yet but I'm guessing it will be around a 1200 lb.
Thanks in advance!
Briansch
Thanks in advance!
Briansch






RE: RTU on Deck
As an example of a higher load, a "hot" lugger for roofing with 15 gallons of asphalt weighs about 175 lbs, and with two wheels, exerts a load of almost 90 lbs and a contact area of about 4 square inches.
RE: RTU on Deck
Briansch
RE: RTU on Deck
When supporting a rtu on metal deck, what I normally do is providing steel channels under the unit. But, for lighter units, i.e. 150#-350#, I would provide 2x's inside the deck flutes to keep the deck from crushing.
SDI/steel deck manuf. normally recommends a 250# max. concentrated load on the deck.
RE: RTU on Deck
http://www.njb-united.com/usd/ddds/data37R.pdf
RE: RTU on Deck
I'm starting to worry about you...you come up with some of the most obscure, yet relevant links. How do you do it?
RE: RTU on Deck
Briansch
RE: RTU on Deck
They have several on-line design aids. Recently, in Modern Steel Construction they printed one for crushing of decking.