Building around duct work

Old 11-20-00, 01:11 PM
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Hello - I have a new home that we are going to finish the basement in this winter. I have read alot about not using 2x2's for the walls. Are 2x2's a logical solution to building soffits around the duct work, or should I use 2x4's?
My walkout wall is ready to drywall, with faced insulation. Should I still put a vapor barrior over this, or is that what the face does? The other walls , well some are like 7' of concrete with a ledge at the top that. I plan on building 2x4 walls all the way up to floor joists, which will leave about a foot of dead space. Should I "double insulate" that space? (Top 1' already has faced insulation in). I have other areas where the concrete is only 3' high, same question, should I add more insulation to the 5' already insulated?
The walls - I was going to use 2x2's where I didnt have drains to get around, but now am wondering after reading on this bb. Regardless, I have no load bearing walls, so I was going to simply use masonary nails on the floor, and nail the top into the floor joist. Do I need to put any nails into the foundation? I have heard that you shouldn't because it can cause it to crack.
I have more, but this is already to long! Thanks for your help!
Old 11-20-00, 06:37 PM
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Here's my preferred soffit.

(1) Screw a 2x2 to the joists on either side of the obstruction.
(2) Screw a piece of 1/2" OSB to the outside of each 2x2, hanging down far enough to clear the obstruction by about 2 inches.
(3) Screw a 2x4 along the bottom edge of the OSB, on the inside. This is mostly to provide something to screw the drywall to.
(4) Screw 2x4s horizontally, lying flat, between the 2x4s, every 16 inches.

If your soffit is small (say less than 2 feet across), you can skip both the OSB and the horizontal 2x4s. But I wouldn't.

If the soffit is wide (say over 4 feet), you may need to put the 2x4s vertically (like a regular joist) instead of horizontally.

There are as many other choices as your imagination allows.
The facing on the insulation does act like a vapor barrier, and if you don't live in an especially humid place, it's probably okay. A plastic vapor barrier over this is just extra insurance for humid climates.

How much insulation you put in is a matter of personal choice and is influenced by the severity of your climate. But insulation is cheap, and more never hurts.
The best wall solution is a full 2x4 stud wall attached only to the floor and ceiling, and not attached at all to the foudation. This gives you sufficient room for insulation, outlet boxes, protects the studs from moisture from the foundation, and provides the straightest wall. A 2x2 or 2x3 wall will just not be straight -- and you may not figure this out until you paint it.

Make sure you use pressure treated 2x4s against the floor. And learn about fire stops, both horizontally and vertically.

Good luck.
Old 11-21-00, 07:59 AM
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Thank you John, that helps alot.
Old 05-19-01, 10:35 AM
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What is a OSB??
Old 05-19-01, 11:06 AM
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Wow, Ron, you sure dredged up an old thread to ask this question.

OSB is Oriented Strand Board. It has applications very similar to plywood, and comes in 4x8 sheets just like plywood. It is commonly used for subfloors (3/4") and wall sheathing (1/2"). It is essentially a bunch of chips of wood glued together. Many people mistake it for particle board, but it is much stronger than particle board, and it holds nails and screws much better. Go to Home Depot and look at some.

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