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Old 07-31-2020, 04:45 PM   #1
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Method of wall framing

There seem to be two prominent methods of adding studs to walls, one that attaches wood (2x4, 2x3, etc) across the ribs, the other in-between the ribs. Below are two pics (not mine) that illustrate. It seems that the "in-between" method will give slightly more interior room but is perhaps a bit more work. Any pros and cons you can tell me about?
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Old 07-31-2020, 08:12 PM   #2
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I'm fairly new to this, but I don't understand all the framing... What is the point of adding studs? Are you trying to make space for more insulation? If so, across the ribs is the only option. If not, don't bother with additional studs. As much as possible, arrange your cabinetry/furniture such that it can be bolted to the chair rail and ribs. Only add studs where you absolutely need to make an anchor point between ribs.
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Old 07-31-2020, 11:02 PM   #3
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Originally Posted by FatBoySTL View Post
I'm fairly new to this, but I don't understand all the framing... What is the point of adding studs? Are you trying to make space for more insulation? If so, across the ribs is the only option. If not, don't bother with additional studs. As much as possible, arrange your cabinetry/furniture such that it can be bolted to the chair rail and ribs. Only add studs where you absolutely need to make an anchor point between ribs.
I think that it’s good to have wood to screw onto if you are paneling the walls.

There’s all sorts of ways to do the walls. I decided that I was willing to lose a few inches in width and just ran 2x2s over the existing aluminum panel and insulate that space.
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Old 07-31-2020, 11:10 PM   #4
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I think that it’s good to have wood to screw onto if you are paneling the walls.
2" (presumably on each side) doesn't sound like much, but that's 5% of your total potential living space. Why is screwing wood to wood to metal better than cutting out the middle-man? I ask because I'm going to be doing my walls over the next 4 days, and I surely don't want to do this twice. Thanks!
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Old 07-31-2020, 11:25 PM   #5
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2" (presumably on each side) doesn't sound like much, but that's 5% of your total potential living space. Why is screwing wood to wood to metal better than cutting out the middle-man? I ask because I'm going to be doing my walls over the next 4 days, and I surely don't want to do this twice. Thanks!
The fasteners used to connect wood to metal are big and not pretty. Once the 2x2 is screwed to the hat channel then a finish nailer can be used to attach panels or T&G to the 2x2.

3% wasted space.

You can put the “nailer” on the side of the hat channel and save the 3%

Use Teks wood-to-metal screws of the appropriate length

https://www.teksscrews.com/products/wood-to-metal
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Old 07-31-2020, 11:38 PM   #6
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How about spraying insulation on the OUTSIDE of the walls, and then wood panel over the foam, now you gain space, and have a woodie. Because everyone loves wood, the more of it you have, the more people love it.



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Old 08-01-2020, 06:53 AM   #7
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Putting insulation inside the cavities between the ribs compromises its effectiveness because of the extremely high thermal conductivity of steel (polystyrene insulation has a thermal conductivity of 0.03 while wood has a value of 0.15, five times worse; mild steel has a thermal conductivity of 54, which is 1800 times worse than polystyrene). In building construction it's estimated that insulation packed between metal studs is 30% to 70% less effective than unbroken material, so 1.5" XPS foam between the ribs of a bus will only be as effective as 1" or 0.5" XPS placed on top of the ribs.

In addition to ease of attachment as others have mentioned, placing wood furring strips on top of the ribs provides a thermal break between the steel ribs and the interior, and allows a greater overall thickness of insulation. It is probably better to run the furring strips front-to-back than directly aligned with the ribs (side-to-side) since this allows the thermal break to mostly be provided by insulation instead of wood (even wood is 5 times worse than XPS as a thermal conductor) and you don't have to worry about bending the furring strips to match the contours of the ribs.

The first pic you linked seems kind of weird, since it seems the insulation is packed between the ribs and then the wood is on top of that, which doesn't really accomplish anything, unless they later filled the gaps with more XPS foam board. There's also no reason for furring strips to be that massive.
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Old 08-01-2020, 08:42 AM   #8
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Thanks all for your answers. I certainly agree on the size of the lumber used, doesn't need to be that big. Does it make sense to put sill plate gasket over each rib before installing the panels to create a thermal break? Or am I overthinking, lol
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Old 08-01-2020, 08:55 AM   #9
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Thanks all for your answers. I certainly agree on the size of the lumber used, doesn't need to be that big. Does it make sense to put sill plate gasket over each rib before installing the panels to create a thermal break? Or am I overthinking, lol
It's a lot better than nothing, but it's basically like 1/4" thick foam. If you use 3/4" instead, you triple the R-value over the ribs at a cost of just one additional inch of interior width.
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