# Floating wall for basement



## pattyobrien3 (Sep 13, 2012)

pattyobrien3 said:


> I had some questions about floating wall construction for a basement - I am just looking into finishing my basement to make it a liveable space. I have a diagram of a floating wall that was given to me by my city's permitting website.
> 
> Firstly, is there a good video anywhere detailing constructing a basement floating wall? I've seen them for basement walls, and attic floating walls, but never basement floating walls.
> 
> ...


Alternatively, I've read that some people nail the walls at the bottom, and have the wall float at the top. This seems sensible from a structural standpoint, but I'm not sure if it is generally considered a good pratice. My diagram does specify floating the walls at the bottom, not at the top.


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## concretemasonry (Oct 10, 2006)

You do not have to "float" the framing attached to the exterior concrete walls because they are fixed to the structure of the home.

Depending on the existing details is may be possible for the slab to rise and the interior walls could need to "float" relative to the real rigid concrete structure that everything works off of for differential movement. Whether the exterior walls are reinforced concrete or reinforced block, they are actually 8' deep beams in a concrete footing.

It is possible for interior slabs and column footing to heave, depending on the soil and the amount of dead load put on them.

In fine finishing of the inside of the exterior walls, you may need to allow a gap in the surface materials to allow a floor to come up and not force movement of the drywall.

Dick


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## GBrackins (Apr 26, 2012)

dick, glad you understood the term "floating wall construction." I over 30 years in design and construction I had never heard it. in my area our footings have to be down a minimum of 48" so frost heave is almost unheard of, in fact the deepest frost I've seen is 24" in Southeastern Massachusetts. Of course we are on the Atlantic so it doesn't get as cold here.


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## pattyobrien3 (Sep 13, 2012)

It might be helpful if I post the construction guide here - the construction of floating walls is detailed on page 3. My question is whether or not the studs are attached to the exterior walls. 

Accoding to the diagram, all wall frames, even the ones touching the exterior wall, need to float. 

The reason for the floating walls, as far as I understand, is that there is a large amount of expansive clay (bentonite) in the area, which can cause the floor slab to rise and fall as it gets wet and dries out. 

https://www.auroragov.org/cs/groups/public/documents/document/010850.pdf

The best thing for me would be a link to a video showing the construction of such a wall, but I have as yet been unable to find one.


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## GBrackins (Apr 26, 2012)

ok, now I understand your problem.


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## joecaption (Nov 30, 2011)

The walls are connected with curtin wall connectors.
http://www.strongtie.com/products/categories/curtainwall_cfs.html


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## GBrackins (Apr 26, 2012)

Interesting detail on page 3. I've never worked in an area with expansive soils like this. it does make sense to have the float at the bottom since it is the slab that may lift. Also any soffit boxes for duct work would be under the 1st floor joists so it would be a lot more difficult.

typically the wall studs are at least 1/2" from the concrete foundation wall so that you would not need to use pressure treated wood. The 3/4" plywood or gypsum board every 10' attached to the sides of the studs (with the board flush to the concrete) are a code requirement for horizontal fire blocking.

I myself have not seen this type of construction but it appears to me that you would place 2x temporary blocking on top of the plate attached to the floor (to provide the 1-1/2" void) then you would lay the sole plate for the wall on top of this. the top plate of the wall is attached to the bottom of the 1st floor joists. you would then cut each studs measuring from the top plate down to the sole plate. once the studs are in place you would then use a 40d driven through the sole plate into the plate attached to the slab (do not drive nail through temporary blocking). once nailed every 24" center to center you'd pull out the temporary blocking.

if I come across a video I'll be sure to post it.

Good luck!


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## mae-ling (Dec 9, 2011)

Where I worked a 'floating wall was used on interior basement walls only.
2 ways to do it. 
If your going with a drop ceiling then you just built the wall 1/2" short shim tight to ceiling, nail floor and joining walls, then on ceiling nail beside the shims and pull the shims out. leaving 1/2" gap for movement.

If the ceiling is to be drywalled. Build the wall 2" short. Nail a treated plate to the floor, nail the wall to the ceiling and joining walls, leaveing 1/2" gap between the bottom plate and the plate on the floor (pwf wood), once again shim tight, nail, pull out shim. Drywall gets attached to the wall but no screws/adhesive into the pwf plate on the floor. Baseboards get attached to the PWF plate on the floor and not to the wall, creates a slip joint.


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## GBrackins (Apr 26, 2012)

patty,

it's not the greatest video ..... but it provides the basics

http://www.youtube.com/watch?v=jl3wjr6pwwA


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## mae-ling (Dec 9, 2011)

good for the floating wall, the drywall should be 1/2" off the floor.


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## henrylarry6 (Nov 2, 2012)

It is always beneficial for us to have floating wall.


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