I am about to start framing my basement walls in a day or 2 and the other day when I was in line at the home depot I opened up one of their how to books and flipped to the section on framing a basement wall.
In there they had something about putting a sill plate nailed to the concrete screws and then framing the wall and screwing it to the top plate but having the wall a little bit shorter then the opening between the top and bottom plate. Then they had between the 2 bottom plates pins to hold the wall from being pushed out.
Long story short the reasoning behind doing this was to leave a gap for if the basement floor heaves or settles at all while still making the wall as strong as possible.

Is this common practice and should I be doing this myself or is it overkill? My floor had heaved in the past but I believe it was only in the first few years as the old finished basement subfloor was built level over this uneven floor over 20 years ago and it was still level when I took it out.

 

Thats over kill as I look at it. A P/T wood for the bottom plate to go on the cement all the rest just wood Would cut all the studs to fit the shortest place put the wall up and just shim the top plate. ED

 

It depends on how expansive your soils are. In some areas, this would be overkill. In other areas, it would be very foolish indeed not to install "floating walls". Damage caused by expansive soils is one of the leading causes of insurance claims in North America. A heaving basement floor can literally push your house off of its foundation.

I suggest you check with your local building department to see if this is commonly suggested or required in your area. In my city, the library has a detailed map that shows how expansive the soils are on a neighborhood by neighborhood basis. The percentage of expansiveness can vary quite a bit even within the same city. Huge class-action suits have forced builders here to be more conservative and use floating walls in almost all new construction. Certain construction techniques for basement floors, however, such as structural wooden floors or structural concrete floors can obviate the need for floating walls. However, these techniques cost more and are not commonly used except in areas where necessary.

 

Good to see another Winnipegger here!
Here's a tip, when you secure the top sill to the floor joists above, you will be using a larger spike, normally a 6 or 8 inch nail. Before you drive that nail, drill a hole slightly larger than the nail diameter in the proper location in the top sill plate and then drive the nail through that hole into the floor joist. This will allow the wall to "slide" up and down in place if the floor moves.

 

I am not to worried about the floor and ceiling getting farther apart, that isn't a big deal, I am worried that if the floor heaves like people have said, it can push the house off the foundation.

Mind you the previous owners had a wall in the basement that ran right under the main beam and there were no problems and like I said the floor hasent moved in 20 years so I should be ok.