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Old 03-03-2009, 02:31 PM   #1
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adding a load-bearing wall


When I search for "load bearing," I see lots of threads about people wanting to remove one. I have the opposite situation - I want to add one...

Where the stair well goes through the floor to my basement, the joists obviously can't span the entire length from foundation to beam. Instead, the joists are tied in to one that runs parallel to the beam, which in turn is tied in to the joists that can span all the way to the beam without interfering with the stair well. Does that make sense? I've attached a crude drawing to try to show.

The joist that runs parallel to the beam is supported by a single 4x4 resting on a concrete block that sits on top of the slab. I can't say I'm comfortable with this, and now that I'm finishing my basement and will be replacing those stairs, I'd like to properly support that joist. I'd like to frame a wall under the joist. Is there anything special needed for this wall to bear the load currently supported by that 4x4? Do I just build a 16" on-center wall that fits very tightly under there, nail the top plate to the joist and fasten the pressure-treated sole plate to the concrete? Is there anything special about a load-bearing wall other than the fact that it bears a load?

Thanks!
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Old 03-03-2009, 02:43 PM   #2
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adding a load-bearing wall


You need to make sure the concrete under the wall is thick enough and concrete is strong enough to cary the additional load without a new footing.

Dick

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Old 03-03-2009, 02:57 PM   #3
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Thanks. How thick is thick enough? 6"? If it's not, how big of an area should I remove to replace with a footing - how wide and how deep?

My slab is 3" thick. Given that this joist system is how the house was originally built, is it likely that there is already a footing under that area to support the load from above?
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Old 03-03-2009, 04:33 PM   #4
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adding a load-bearing wall


Based on your drawing I'd say that one joist/beam perpindicular to the floor joists (taking 50% of each joist's load) is probably inadequate. A steel beam or LVL/PSL is typically called for in this scenario to deal with the floor load. One 2x10 isn't enough 90% of the time. So, a properly supported load bearing wall is a great idea if you have the footing for it.

Normally posts that support the structure above a basement bear on pad footings...Say 36"x36"x12" arbitrarily. The pads are located under the basement slab.

To support a conventionally framed bearing wall on a basement floor, you definately need a footing under the slab for the entire length of the wall. Most basement slabs are in the range of 4" thick, and the footing element has to be at least 8" thick...Perhaps more depending on the imposed loads.

Another option would be to determine if you currently have a pad footing (or footings) under the existing post (or posts). If so, a wall can be framed containing some steel lally columns to support the beam. Or, a header can be installed from bearing point to bearing point to provide good support to the floor above, while transferring the loads to two bearing points at each end.

Any chance you can post photos?

(nice chocolate labrador by the way)
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Old 03-03-2009, 04:36 PM   #5
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The size of the footing must usually be determined by an engineer. Too small and your house settles. Too big and....Well, too big usually isn't a problem.
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Old 03-03-2009, 04:48 PM   #6
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adding a load-bearing wall


I think my drawing may not be quite accurate - I think there may be two 2x10s side-by-side there, not one. I'll take some pictures tonight and post them.

Also, I think there probably used to be a lally column or two under there and the previous owner may have cannibalized them for another "project," and replaced them with this 4x4-on-a-block setup. In another area, there are two telescoping columns holding up a 10' section of 4" steel I-beam. This bears no load. No, he used for... and engine hoist. No joke. He would throw chains over the beam and pull down on the chains to lift an engine up and out of the bay. My neighbor (and the P.O.'s old drinking buddy) told me this.

I kind of like doing things right, so I may go ahead and break up the slab there and pour a footing to support a load-bearing wall. I've done plenty of concrete work before and have a mixer like you could rent from the big box. I just hate the idea of all the dust I'll make drilling holes in the slab with the demolition hammer to break it up...

I like your lab pic, too. I saw the full-sized one on your bathroom remodel thread and laughed. Mine is a big 90 lb guy, solid muscle. He can put his front paws on my shoulders and lick my nose... and I'm nearly 6'3". We have another one, but she's a scant 55lbs and about 20" tall at the shoulder. I've attached a pic of them both.
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Old 03-03-2009, 07:30 PM   #7
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Alright, I have pictures. Six of 'em. From different angles. Hopefully you can see what I have going on here. Of interest is the shim-job done where the joists intersect. You'll see...



Ignore the glowing eyes. That's just a yeti.





Here you can see what I was talking about with the shims. What should I do about this:





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Old 03-04-2009, 12:18 AM   #8
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Does it appear that there were posts there at one time?
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Old 03-04-2009, 08:19 AM   #9
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No, it doesn't. There are no marks on the floor under those shimmed hangars to suggest posts used to sit there. The surface of the slab is not marred, nor does it look like any patch work was done if a post that was set in the concrete was removed.

Maybe there were wooden posts there. Maybe they rotted so he took them out and replaced them with the one post seen here. The house had a horrible problem with water in the basement. That might be why he put the post on a concrete block. Before we did our french drain, water would come through the walls and would also rise up through the old cast-iron floor drains. The p-traps under them were broken, so ground water could find its way in through those holes. During hurricane Ivan, we had 4" of standing water on the slab that we had to pump out. I can only imagine how long the p.o. lived with that water problem. We fixed it within a year of buying the place.

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