Question: I want to finish my basement; however my home sits on clay
soil. I am concerned about my basement floor heaving and settling throughout the
various seasons of the year. Is there any thing I can do when framing
basement walls to allow them to float up and down?
Answer: If you live
in an area that has expansive clay soil in it, it is imperative that you build
floating basement walls in the basement when finishing the basement. As a matter of fact,
many municipalities that are located in expansive clay areas have codes
requiring it. If you do not install floating basement walls in the basement it is very
possible that when the clay soil expands the basement walls could lift the floor
above off the foundation sill and/or cause structural damage to the home.
Framing basement walls can be a tricky endeavor, even when the home’s
foundation and basement floor is resting on solid bedrock. Framing basement
walls in a home that was built on clay creates even more of a challenge, however
it is not insurmountable. Floating basement walls can be constructed to handle
expanding and contracting soils. Floating walls can be created by creating a 1
to 1.5 inch gap at the top of or bottom of the wall.
Though many prefer creating the gap at the bottom of the wall since you can
hide the gap with baseboard trim, I prefer creating the gap at the top using
some relatively simple technology.
Managing the Clay Soil
First, there are ways to manage
the clay soil to minimize basement floor heaving and settling. In
particular, it is important that water run off from the roof be directed
away from the home. Second, the back-filled soil around the home’s
foundation should be sloped away from the home, again to allow water run-off
away from the home. Third, a perimeter drain should be added around the
foundation, if one was never installed.
These three tips can help to
minimize water from seeping around the foundation and causing the clay to
become saturated, which leads to heaving basement floors.
These clips will enable the basement walls to breath (move up and down), but give the
support necessary to ensure the wall remains vertical.
When framing basement walls there are typically many obstructions (pipes,
duct work) that you need to build around. Thus, it is sometimes easier to stick
build walls around these types of obstructions.
When framing basement walls, particularly when you are stick building the
walls, a nail gun such as the
Bostitch F21PL Round Head 1-1/2-Inch to 3-1/2-Inch Framing
Nailer with Positive Placement Tip and Magnesium Housing,
can make the job go a lot faster and smoother. If you don't want to buy one, then
you should at least look into renting one. A nail gun works much better than a hammer when
toe nailing studs into floor or ceiling plates.
An alternative to keeping the clay
soil at a consistently low moisture level is to keep it at a consistently high
moisture level. The installation of some type of pipe irrigation system around
the home can be used to keep the soil at a consistently high moisture level to
prevent the clay soil from shrinking during the dry seasons.
Beyond attempting to manage the clay
soil moisture levels around your home, you can also construct your basement
walls such that they effectively float up and down as the clay soil expands and
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Framing Floating Basement Walls
When building your basement walls,
you can attach L-shaped steel framing brackets to the top of the basement walls
and then connect the vertical member of the brackets to the floor joist or
blocking material. Structural nails, recommended by the bracket manufacturer,
should be used. The nails secure the bracket to the top of the wall plate and to
the floor joist / blocking material. The nails are installed in the vertical
channel of the L-bracket, that is attached to the floor joist / blocking
material, so that that the floating basement wall can slide up and down
The L-shaped brackets allow the floor
to move in the vertical direction but not in the horizontal direction. As a
result, your basement walls stay plumb, and can breathe as the clay soils expand
and shrink throughout the year.
When finishing a basement in a
expansive clay soil area and creating a gap at the top of the basement walls, a
dropped ceiling may be your best alternative for hiding the gap.
For more help on Finishing
Basements, see HomeAdditionPlus.com's
Basement Remodeling Bid sheet. The
Basement Remodeling Bid Sheet will help
ensure that your hire the right contractor so that your basement remodeling
project is done
correctly and you get the project finished on time and budget.
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