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walt1122 07-04-2009 01:35 PM

Engineered Joists & holes for HVAC ducts
Hi tried this post under the HVAC heading but wonder if it shouldn't go here cause I need advice on engineered joists and not necessarly HVAC.
Hi, builder didn't follow my request to keep ceiling height in the garage at 10 feet by allowing the HVAC contractor to install the flex duct below the ceiling and then the builder box'ed it in and covered with sheetrock right down the center of the entire garage. Well I'm now at about 8 feet and can just barely fit my Kobota with its rollover cage into the garage. Had planned on having a place for shelving etc., etc. The garage is really not what I wanted and I'm looking for ways to fix it without costing me my left lung. The HVAC contractor offered to run sheet metal ducts that would be only 5 inches deep and 20 something wide. I have an apartment on the second floor where we live so some kind of duct work in necessary. I have a heat pump to handle our heat and air conditioning needs. The price to change out what I have with what the HVAC contractor offered is just too much to spend right now and I was just thinking about it today and... Well that is why I'm here. I have an open span across the garage thanks to the engineered lumber that spans the 24 food deep garage. The engineered joists are about 16 inches tall and I was wondering how much I can cut out of the center plywood sections and possibly run duct through them. Yeah I know they should have used trusses and I could have run the ducts easily thru them. Well I asked for that and got this. So here I am. And any all suggestion would be appreciated.



Yoyizit 07-04-2009 03:49 PM

Couldn't open your links.

Replace the wood with metal I-beams?
Bolt long flat plates of steel or angle irons to the wood areas that you will not be removing?
Use a center support column?

The deflection in the center, before and after, will tell you if you made it strong enough.

Michael Thomas 07-04-2009 05:13 PM


however check the specific manufacture's requirements:

Also, see here for many details of I-Joist construction.


Home Inspection: "A business with illogically high liability, slim profit margins and limited economies of scale. An incredibly diverse, multi-disciplined consulting service, delivered under difficult in-field circumstances, before a hostile audience in an impossibly short time frame, requiring the production of an extraordinarily detailed technical report, almost instantly, without benefit of research facilities or resources." - Alan Carson

walt1122 07-04-2009 07:37 PM

Hi Michael Thomas and Yoyizit, thanks for the suggestions and especially for the reference material from you Michael. Based on item 4. sounds like I can cut away most of the web to accommodate putting in the round flex. I will check with the I-beam manufacturer to see what they say and see if they have anything to say about doing anything like this with their product. The I-beams are currently covered with fire code sheetrock on the ceiling of the garage. I am just looking at possible methods and haven't made any decisions yet.
Yoyizit, Iím trying to not have any columns in the garage area. Only as a last resort would I consider a steel I beam. Itís probably to costly to do just for this purpose. I would rather shell out the few thousand dollars to revamp the duct work from round flexible to rectangular rigid instead of doing all the structural changes.

Thanks again for the help.


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