Soffit hell - Supporting wide and long soffits

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Old 04-17-14, 01:33 PM
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Soffit hell - Supporting wide and long soffits

Hello,

I have to create a really wide soffit, about 6' wide. I don't want the ceiling to sag so I am looking for a good approach to supporting the structure. I have about a 4" space between the duct work that I "might" be able to add some support (wish the builder had put an I beam here.

I have stared at this ceiling for hours trying to figure out the best approach. My thought was to attach a 2x4 to the doorways (left). Run flat 2x4 16" OC across the ductwork. Attach the 2x4 to a ladder I create on the other side (right) of ductwork.

I am planning to drop the ceiling height to the height of the soffit for the area, but raise it again when I get into the rec and bedroom areas.

I am thinking my builder did not do me any favors...
 
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Old 04-17-14, 05:17 PM
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You could do that but its a little thick, heavy and overly complicated.

You might instead look into using i-beam and hat channel, suspended from tie wire.
 
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Old 04-17-14, 05:19 PM
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Or, spray everything up there flat black and make it disappear. Really too busy and too wide for you to run joists and maintain head room, IMO.
 
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Old 04-17-14, 09:23 PM
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The ducts have 94" below so there should be decent headroom ... Provided the ceiling does not come down.

Guess the better question is whether I can use 6' boards across without fear of sagging or falling apart. If so, I am thinking I need to figure out a way to move one of the ducts to gain access to an existing beam. Thanks!
 
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Old 04-18-14, 04:59 AM
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Any lumber you use will need to be edge installed just like your joists so they won't sag, thus my comment regarding headspace. A 2x4 which would be minimal will take up 4" of space with covering, bringing your clearance to 90". If that is acceptable, then you can frame it all in using standard construction methods, apply your sheetrock and have a 90" ceiling.
 
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Old 04-18-14, 05:27 AM
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Plus you really don't want any of the framing touching the ductwork, or it may "creak" with expansion and contraction. So add a bit of clearance to that 4" as well. If you go that route, you will need to fit solid blocking- maybe 24" on center- between the outer pairs of I-joists since you can't get to the middle ones (ideally more I-joist, similar to the blocking detail shown on page 5 of this PDF) and then suspend your framing from that.
 
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Old 04-18-14, 11:23 AM
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Thanks for the PDF, lot of good info there. I don't want to put my 2x4s on edge, that would get pretty low.

I am going to figure out a way to shorten the unsupported span. I may be able to install some blocking between the I joists you can't see and drop a ladder in the gap you can see, keeping the unsupported length less than 4ft.

What has better support hanging a ladder on 1 I beam or attaching it to blocking that exists between 2 I beams?

Thanks so much for the advice...
 
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Old 04-18-14, 02:08 PM
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I also had a fairly wide soffit to build on one of my basements, but it was not as wide as yours. I still used wood, ripped 2x4's into 2x2's to go across. Don't over think this, simpler is better and remember it is not like its a load bearing structure.
Looks like you have engineered wood I-beams for your floor joists above. You also have some slits or spaces between the ducts. You could cut a 2x6 to fit in the width of the I-beam so it rests on top of its bottom lip. i picked a 2x6 only because it gives a nice flat base. Screw a metal strap to the bottom of the 2x6 so it is in the middle of one of your duct spaces (openings) long enough to hang down to support your soffit cross piece. Slide it down between the i-beams to where you need it to support the soffit cross piece, then screw the strap to it. If you somehow squirt glue on the edges once it is in place it will stay where you want it.

I ended up temorarily lowering my ducts by removing their supports / straps in order to get enough room to screw in some support pieces. Just use your ladder or even stacked boxes as temorary support for the ducts while you work. Lowering the ducts is a messy job. For me I was able to get inside those main ducts and clean out all the saw dust & construction debris left behind. I had insulation, chucks of wood, nails, and scrap electrical wire in mine.

Before you close it in or put it back up in place, buy a roll of Duct tape (not the cheap fabric stuff, but the foil / metal type) and tape every seam, junction,& saddle. You will be amazed by how much leakage occurs. No need to heat & cool the enclosed soffit space.

Good luck. Mike
 
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Old 04-19-14, 07:02 AM
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It is starting to come together in my head...

I will add blocking between the unseen I joists. The blocks will sit and attach on top of the I joist lip. This is stronger than flush blocking?

I will add metal straps that hang from the new support. The straps will hang down and connect to a new cross support that sits perpendicular to the 6' long 2x2s. Would it be stronger if my perpendicular support completely intersected the 6' span?

Can't wait to see what is sitting in my duct work

Thanks for the great ideas!
 
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Old 04-19-14, 09:24 AM
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Just to throw another wrench in the mix, but have you considered framing it with steel studs? I do a lot of commercial work and have seen very large soffits that are framed with steel and 5/8" rock. Soffits are great for steel because you will not be attaching any wood trim to them.

Framing with steel is also easier than wood in this case because you would put it together all with screws (fine thread) and tin snips. You use tracks on the ends and you could use as small as 2 1/2" or 1 5/8", depending on your spacing.

Google "framing soffits with metal studs" and you will get many hits to check out. Also check the images section.
 
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Old 04-21-14, 01:55 PM
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Thanks for all the ideas!
 
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Old 04-22-14, 10:11 PM
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yes, just use 1 5/8" metal studs. And the hot/cold from the ducts won't make them expand like wood but you still might get cracks in your plaster from them.

Get a vertical support to the frame you're sheetrocking at least every two feet if possible. I think I've even seen inspectors pass metal supports screwed into the duct but I'm not suggesting that. At the least, it would cause duct cleaning tools to get caught on them and possibly rip up etc.
 
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Old 05-07-14, 07:20 PM
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you can even connect many drill screw tip shafts to make like a 2' extension to reach in between the ducts. It will probably be wobbly but the magnetic tips should hold the screws on or even lightly glue the screws to the tip that will break away while installing. Maybe predrill the metal studs since they're harder to screw through then the wood joists.
 
 

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