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June 9, 2009
a/c rooftop dunnage
A prior poster wrote: "Not all roof top a/c units need their own separate steel support framing ..." Does anyone know who can spec out the dunnage? Our architect drew up plans to run iron beams across the parapets and every contractor we talked to said that was unnecessary and overly expensive. What is the right way at the last cost? Does anyone have any recommendations? Thanks / Iddelz
Comments
dunnage
One entry found.
Pronunciation:
\ˈdə-nij\
Function:
noun
Etymology:
origin unknown
Date:
15th century
1: loose materials used to support and protect cargo in a ship's hold ; also : padding in a shipping container2: baggage
Retrieved June 9, 2009, from http://www.merriam-webster.com/dictionary/dunnage
Posted by: Bklyn Fire Alarm Guy at June 9, 2009 11:42 AM
Your architect is the sole party responsible for the specification of the dunnage. Unless the contractor has an architectural or engineering license and is willing to supercede the architect for the dunnage, this is not a question that's normally open to opinion polling.
The architect may well have reasons for the sizing the dunnage that the contractor isn't aware of; that scenario (there are others) makes it easy for a contractor to take a quick glance and make the claim that it's oversized. The contractor may even be right, but that has nothing to do with the issue.
I suggest you convey the opinions of the contractors to the architect, and see if he or she can come up with any alternates that would be acceptable and meet their standards.
Posted by: Smokychimp at June 9, 2009 11:52 AM
All the roof units on my block are on beams on parapets. That's not definitive but I doubt it would've been done everywhere if it weren't necessary.
Posted by: Arkady at June 9, 2009 11:59 AM
Smokeychimp is completely correct. Dunnage is not always required but it usually is best in brownstones for two reasons, one is structure borne vibration/noise in a weak roof, the other is the unit may settle into your many layered roof as it heats up in the summer. Sometimes you can set the dunnage in a corner with much shorter steel. Also many architects/engineers build with a safety factor of 10, but it is their license.
Posted by: edifice rex at June 9, 2009 12:38 PM
hi smoky: i've taken your suggestion and asked the architect. however, so far he has been wrong with just about every regulation issue we've faced so that's why i'm seeking alternative solutions.
our architect is just a glorified designer - a v. good designer in my opinion - but lesson learned for everyone on a major project: design is just a small part. you need someone who knows the code, knows the way around the code and knows people who can implement every portion of the plan beyond surfing "lightinguniverse.com" / iddelz
Posted by: iddelz at June 9, 2009 12:39 PM
Iddelz I do sympathize with you and please note I am not trying to say who's right in this case, just that there is a question of legal responsibility that becomes a bigger factor than even common sense sometimes.
Posted by: Smokychimp at June 9, 2009 12:49 PM
Re dunnage not always being required: we went through this recently with the installation of our a/c system. We were told that dunnage IS necessary if the air handlers and/or condensers are too large to be placed inside the house (in a dropped ceiling, for example). The dunnage is required for fire reasons - the condensers themselves are only 150 pounds or so, but one resting directly on the roof is an immediate hazard if there's a fire, as it becomes a 150-pound deadweight plummeting through every floor of the house.
We did the parapet-spanning beams instead of a corner installation and didn't think the price was outrageous. Whether you can get narrower beams that your architect spec'd or a corner set-up, the main cost is the permits and cranes and the actual cost of the beams after that is pretty marginal. Can I ask what prices you're getting?
Posted by: zeebee_in_bklyn at June 9, 2009 1:22 PM
We will be putting a/c units on the roof in our reno. The architect brought in a structural engineer to look at the situation and confirm the type and amount of dunnage required so that the job will be done to code. If you haven't had an engineer look already, ask your architect to arrange a consult.
Posted by: Silvermax at June 9, 2009 1:25 PM
I've placed them directly on pads on roofs in the past without DOB issue. I did have an issue once because we didn't put a GFI outlet next to the unit on the roof. For some reason the DOB requires it . . .
Posted by: IronBalls at June 9, 2009 2:24 PM
zeebe: the initial quote was $3,500 to put iron beams on the roof for the condenser plus $3,000 to bring power to the roof. i'm looking for alternatives, then i'll negotiate. note that i don't live in a brownstone but a detached brick square.
i was quoted $11.5 for the system itself, a 3-ton 13 SEER carrier + air handler + ductwork installed. i wasn't going to install a/c at all but the beam rafters are exposed, they're high and i thought the price was good. / iddelz
Posted by: iddelz at June 9, 2009 2:49 PM
For that size I would definitely get the steel. zeebee has it right -- the actual cost of the steel beams ought to be fairly minimal considering everything else you're doing. Plus, remember that the reason it's required is for the safety of firefighters -- they don't want a huge unit falling on top of their heads. It's just the right thing to do.
Posted by: josh59x at June 9, 2009 11:15 PM
The steel dunnage is a Fire Department code requirement. It is relatively new and not all contractors know about it. We ran into it recently when we were doing a reno. Expeditor said it wasn't dob, but was fire code - and that they are working on getting the two aligned. A few years back a unit came through the roof and killed a firefighter, and that's why it is part of the new code. You do need it. the architect is right in this case.
Posted by: homey at June 10, 2009 11:46 AM
Iddelz, that quote doesn't sound too bad. When negotiating the contract payment schedule, our a/c guy estimated that the cost for the crane, permits, steel and two guys on the roof to set the beams in place and mount the condensers was around $5000. We had electrical in the electrican's contract and our overall system cost was higher than yours, plus we're in a rowhouse, so it's hard to compare apples to apples but at first glance that price isn't outrageous.
Posted by: zeebee_in_bklyn at June 10, 2009 12:50 PM
your quote is reasonable...the dob has been turned into a fee geneator under bloomberg, so there is no more of the 'getting around code
Posted by: eman1234 at June 10, 2009 7:21 PM
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