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I have a 20 year old house (which is a basic colonial box). The basement has a standard poured concrete exterior wall. Against the concrete exterior wall, they framed a standard wood 2 x 4 wall, filled the bays with fiberglass insulation and covered it all with a plastic sheet, which I guess is a moisture barrier of sorts. I would like to rip out the insulation and framed wall and replace it all with foam boards (DOW Thermax). My question is, how do I know that the framed wall is not load bearing in any way? I'm 99.9% sure from what I've read that it's the concrete wall holding up the house and the framed wall is just there to hold the insulation in place and possibly to add sheetrock to in the future.

I know that people might be nervous to answer questions about load bearing walls. I'm just looking for some general advice rather than a definitive answer.

EDIT: Here's a photo of the rim joist area. The framed wall at the front is the one I'd like to remove. From the answer below, it sounds like the joists are indeed sitting on the concrete wall.

enter image description here

EDIT 2: Somebody commented that I have no insulation in the rim joist. I actually pulled out the fiberglass to take this photo. I then replaced it with a block of 2" XPS foam board and used spray foam around the edge. I luckily have access to a thermal imager from my employer, so I took some images. Here's an image of no insulation (lots of heat loss):

enter image description here

Here's the original fiberglass. It does a good job, though there are some obvious cold spots from air leakage:

enter image description here

Here's the new 2" of XPS with spray foam around the perimeter. It also does a good job and it's more even. However, I'm surprised that there are still cold spots around the edge. It was tough to maneuver the spray foam gun in the tight area and I may not have done the best job:

enter image description here

Finally, here's a side by side of a fiberglass next to XPS:

enter image description here

Overall, I'm not sure there's a big enough improvement to warrant the cost. I think I could do a better job with the spray foam and a second piece of foam would obviously improve things. Aesthetically, I do like the clean look of the foam boards.

Getting back to the original question, here's a photo of the framed wall with the fiberglass insulation. Again, the fiberglass does a decent job, but there are some cold spots.

enter image description here

  • Cool pictures - motivating me to get down in the crawl space and insulate my rim joists. – CoAstroGeek Jan 19 '15 at 18:10
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The 2x4 wall is certainly not load bearing in terms of the floor joists, etc. The floor joists will be supported by the concrete walls, and possibly by a beam or wall somewhere along the span. Since the wall in question is right next to the concrete outer wall, it won't be supporting the joists. If the ceiling isn't finished you can likely see for yourself that the ends of the joists extend out over the concrete wall.

If a mid-span wall is supporting the joists, it should have a double top plate, and king studs around doors and such. Otherwise, it is likely just a non load-bearing dividing wall. You can also measure the joist depth and length and compare to span tables to see if a mid-span wall is likely to be load bearing. If you have TJI joists (OSB web with laminated top and bottom) it may be a little more difficult to identify your joist.

If you have a suspended ceiling or such, it may be involved with this wall. And you might have wiring or plumbing in it. But it's not holding up the house.

  • While you're probably right, you should say WHY the 2x4 wall is not holding up the upper floor and how the questioner can see for themselves why it's true. – The Evil Greebo Dec 29 '14 at 20:40
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The simple answer - you can be sure by looking at it. You need to be able to see up between the joists where they go over the concrete wall. There should be a sill plate on top of the concrete wall, and then the joists should sit on that. If so, the concrete is supporting the joists.

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Where are you located? Unless you are in an extremely cold climate what you are suggesting is a waste of money.

I noticed that you said you wanted to change the insulation (which I doubt gives you a noticeable difference yet you have no insulation over the header in between your joists. About 70-80% of your heat loss in a basement is happening right there. Don't spend money on making the 20% a tad better. Fix the real problem.

  • I'm in Vermont, so it does get pretty cold up here. I removed the fiberglass insulation from the rim joist to take the photo. I edited the question above and included some thermal images with various types of insulation. – Ben Mills Jan 19 '15 at 14:21

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