# Floating Basement Walls



## jonhayden (Jun 27, 2012)

Hey all,

I'm going to start finishing my basement soon, but was hoping for a little help with floating the basement walls. Surprisingly, there is VERY little info on the web on how to do this. For those of you not in Colorado, this is required by code here because of the soil, and is constructed like this:










By constructing the walls this way, they "float" and if the floor moves up or down, the wall won't push the first floor joists up and cause damage. The image above is how you float them on the bottom. But in my town, you are also allowed to float the walls at the top instead of the bottom. I haven't been able to wrap my head around floating them at the bottom due to these reasons:

1) How can you attach a tile shower or bathtub to a wall that floats at the bottom? If the tub is attached to the drain in the floor, but also attached to the part of the wall that doesn't move, it would destroy the tub/shower. So I'm guessing that in this case you have to float the shower/tub at the top...just not sure how walls floating at the top can connect to walls floating at the bottom.

2) What if you want to have a subfloor for carpeting? If the 3/4" OSB, carpet padding, and carpet end up being as high as the bottom plate, what do you attach the baseboard to? It would have to be attached to the gap (air) between the 2 base plates. Haven't figured that one out either.

3) How do you install a pocket door? Good luck finding a pocket door kit that works with bottom floating doors.

So these are a few reasons I decided to not do a bottom floating wall even though that seems to be the way it's done 99% of the time. With a top floating wall, I eliminate all these concerns. It allows me to frame the basement like any other wall in the rest of the house. I don't even have to worry about the gab below a door shrinking and growing do to the soil expansion.

And then...I woke up in a panic last night because I forgot about the egress windows. If I float my walls at the top, but also attach those walls to the window frames, what happens when the floor moves up or down? Won't it destroy my window framing since the floor with the wall will move, but the the window won't? Or can I somehow "float" the window framing so it isn't attached to the exterior wall that can possibly move up and down?

So if I decide to go back to the drawing board and do my floating at the bottom, I still have to solve my issues above. I can probably come up with something for #2 and #3, but #1 is still puzzling to me.

Any comments welcome since I'm not even sure if I have a specific question. Just hoping someone can enlighten me on a good solution.

Thanks,
Jon


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## brockmiera (Oct 9, 2012)

I had similar questions when doing my 1950's ranch in Littleton. My main question was regarding the continuous curb footer in the basement that has a load bearing wall. If that footer moves then the whole house moves. I asked the inspector about floating walls and he said, "Well it hasn't moved in 60 some years, I doubt its going to move now. 

I hope you can figure it out. My buddy had his basement finished in Centennial a few years ago and it has floating walls. I'd be more than happy to pass along the contractors information if you'd like to pick his brain.


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## Canarywood1 (May 5, 2012)

Doesn't your building department have any information on wall construction?


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## jonhayden (Jun 27, 2012)

brockmiera said:


> I hope you can figure it out. My buddy had his basement finished in Centennial a few years ago and it has floating walls. I'd be more than happy to pass along the contractors information if you'd like to pick his brain.


Thanks! If you have a contact that doesn't mind me asking questions, that would be great.


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## jonhayden (Jun 27, 2012)

Canarywood1 said:


> Doesn't your building department have any information on wall construction?


Yep, they have a 4 page building guide they provide, but it doesn't address any of my concerns. Of course I do plan to get a permit and will have more access to the inspector at that point. But I'd like to get my plans figured out and maybe put up a couple walls first. Email response from them have been slow.


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## jonhayden (Jun 27, 2012)

Okay, I was thinking about the window problem I would have if I float the walls at the top. Instead of framing the window so the 2x4s are in line with the concrete edge of the window, I'll bring the framing in about 1.5 inches on the top and bottom. So when I attach the window trim on the top and bottom 2x4s, it won't be touching the concrete window edge. That would allow the floor to go up or down 1.5 inches. Hope that makes sense.


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## 47_47 (Sep 11, 2007)

Not to highjack your thread JonHayden, but when you build floating walls how do you determine your starting level? I mean if when you build with the soil at its highest point with the 3" gap, when it moves won't your gap increase?


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## hand drive (Apr 21, 2012)

building the wall like the diagram shows would require the wall to hang from the floor system above, probably an upside down balloon framed type wall that nails directly to the sides of the floor joists and the top plates are added afterwards between the studs. it seems much easier to frame the spaced gap to the top of the wall.





47_47 said:


> Not to highjack your thread JonHayden, but when you build floating walls how do you determine your starting level? I mean if when you build with the soil at its highest point with the 3" gap, when it moves won't your gap increase?


how will someone know at which place the heave point is at right now, is it heaved up or heaved down, this is a good question


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## jonhayden (Jun 27, 2012)

47_47 said:


> Not to highjack your thread JonHayden, but when you build floating walls how do you determine your starting level? I mean if when you build with the soil at its highest point with the 3" gap, when it moves won't your gap increase?


Code in my town requires a minimum of 1.5" gap between the 2 plates. But I typically see a 2" to 3" gap. But that's the starting gap. I also typically see the 60d spike stick out the top of the plate another inch too so the floor could also move down instead of up. It is a good question that I've thought about already, which is why I do plan to have the spike stick out past the plate so it can expand as well as contract.


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## jonhayden (Jun 27, 2012)

hand drive said:


> building the wall like the diagram shows would require the wall to hang from the floor system above, probably an upside down balloon framed type wall that nails directly to the sides of the floor joists and the top plates are added afterwards between the studs. it seems much easier to frame the spaced gap to the top of the wall.


Yep, it's just a typical wall that is attached to the floor joists above. The normal way to build it is to:

1) attach the pressure treated bottom plate to the concreate. 
2) place a loose 2x4 on top of the bottom plate (don't attach)
3) Measure from the floor joist above to the top of the loose 2x4
4) build wall for that measurement
5) put the already assembled wall on top of the loose 2x4
6) attach wall to floor joists above
7) remove the loose 2x4 spacer (this gives the 1.5" minimum gap)
8) attach your spikes through the bottom plate on the wall to the PT plate on the concrete

Now you have your gap at the bottom. But the gap at the bottom gives me all kinds of grief. It seems to make sense to me to have the gap at the top, but like I said the most common way to do it is have the gap at the bottom...there must be a really good reason for this, but I don't know what it is.


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## hand drive (Apr 21, 2012)

jonhayden said:


> Yep, it's just a typical wall that is attached to the floor joists above. The normal way to build it is to:
> 
> 1) attach the pressure treated bottom plate to the concreate.
> 2) place a loose 2x4 on top of the bottom plate (don't attach)
> ...


most likely because the wiring and plumbing etc will be in the main part of the wall and will stay attached to the wall and floor system as one piece save for the 1 1/2" at the bottom where it floats. if the top of the wall floats then the wiring , plumbing, in the wall will get crimped or bent. It does seem that having the play in the underside of the wall is the ticket and I would use 1 1/2" 2x4 spacer blocks instead of a whole 2x4 for the spacer, will be easier to take out once wall is complete...


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## jonhayden (Jun 27, 2012)

hand drive said:


> most likely because the wiring and plumbing etc will be in the main part of the wall and will stay attached to the wall and floor system as one piece save for the 1 1/2" at the bottom where it floats. if the top of the wall floats then the wiring , plumbing, in the wall will get crimped or bent. It does seem that having the play in the underside of the wall is the ticket


Yeah, I'm still a little confused on this. All the plumbing is attached to the floor so I'm not sure what would get pinched or stretched if the wall was attached to the floor and floated at the top. Of course I will be running pex tubing across the ceiling so I feel as long as I provide enough tubing, it will handle the movement. Same for electrical...if I add a loop or two of extra wire it will be okay. But you're probably right about the reason.



hand drive said:


> and I would use 1 1/2" 2x4 spacer blocks instead of a whole 2x4 for the spacer, will be easier to take out once wall is complete...


Definitely. I just wasn't clear.


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## COKarl (Dec 14, 2013)

*Gap at top breaks drywall*

When the concrete lifts the wall, the gap at the top of the wall will compress, and the drywall will compress and break too. If the wall sags, the gap will get larger and the drywall will separate from the wall and ceiling. If the gap is on the floor, you don't have these problems because the drywall doesn't touch the floor anyway. If the gap increases, orifice the gap decreases and crushes the drywall, it's all hidden behind the baseboard.


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## jonhayden (Jun 27, 2012)

COKarl said:


> When the concrete lifts the wall, the gap at the top of the wall will compress, and the drywall will compress and break too. If the wall sags, the gap will get larger and the drywall will separate from the wall and ceiling. If the gap is on the floor, you don't have these problems because the drywall doesn't touch the floor anyway. If the gap increases, orifice the gap decreases and crushes the drywall, it's all hidden behind the baseboard.


If you float your wall at the top, you leave a gap at the top with the drywall too. You hide the gap with crown moulding. It's just like hiding the gap with baseboard when you float at the bottom.


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## GBrackins (Apr 26, 2012)

just one suggestion, instead of adding nailing strips to the side of the treated base plate why don't you just rip a wider base plate down to size?


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## jonhayden (Jun 27, 2012)

GBrackins said:


> just one suggestion, instead of adding nailing strips to the side of the treated base plate why don't you just rip a wider base plate down to size?


I actually already finished the bedroom. This is an old post. I floated at the top and passed all my inspections without issue. Floating at the top was really easy to do and the crown moulding hides it nicely.


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