BASEMENT FLOORS

Preparing a concrete floor for carpet, laminate, vinyl, or wood flooringhas been simplified by the introduction of new subfloor products that havebuilt-in vapor barriers and cleats that create a slight air gap between thesubfloor and the concrete slab. This system allows air to circulate,protecting the finished flooring from any slab moisture. The new dry-floorsubfloor systems are less than one inch thick and are very easy to install.

There are several types of these dry-floor systems available, but the one
most readily available and easiest to use is a product sold in 2 × 2 feet
tongue-and-groove squares.
Although subfloor panels can be adjusted for slight irregularities in the
concrete slab, they can’t overcome problems with a floor that is badly
cracked and heaved. Nor is the built-in air gap beneath the system a
solution to a basement that has serious water problems. A badly heaved
slab will need to be leveled with a cement-based leveling compound, and
serious water problems will need to be rectified before you consider
creating finished living space in a basement.
Allow the subfloor panel squares to acclimate in the basement for at
least 24 hours with the plastic surfaces facing down before installing them.
In humid summer months, the squares—as well as the finished wood
flooring product, if that’s what you’ll be installing—should be allowed to
acclimate for a full two weeks before installation.
The old way of installing subfloor (plywood over 2 × 4 sleepers) does
make a sturdy floor and has the advantage of not requiring any special
products—you can do it with materials found at any building center.
Instead of a subfloor and plywood underlayment, some flooring
requires an isolation layer to separate it from the concrete basement floor.
These are most often installed with ceramic floors.
If your concrete basement floor has cracks, holes, or other
imperfections, address them before installing flooring.

Concrete basement floors have a high utility value, but whenever possible you’ll
want to cover them to improve livability in your new basement rooms. Some floor
coverings can be installed directly over the concrete, but in most cases you should
lay subfloor panels and underlayment before installing the floor covering. A system
like the one above is ideal for basements because it can be removed readily: the
laminate strip flooring snaps together and apart; the underlayment is unbonded and
can be rolled up; and the subfloor panels also are snap-together for easy removal and
re-laying.

Apply Floor Leveler

Use floor leveler mix or a mortar mixture to fill in small dips in the concrete floor.

LEVELING BASEMENT FLOORS

Test the floor to see how level it is. Use a laser level to project a level line on all

walls. Mark the line and then measure down to the floor. Compare measurements to

determine if floor is level. If you are installing a subfloor you can correct the

unevenness by shimming under low areas. But if the floor height varies by more than

an inch or two (not uncommon), you should pour floor leveler compound in the low

areas. In more extreme examples you’ll need to resurface the entire floor.

Break up and remove very high areas or eruptions, and patch the area with concrete

that is leveled with the surrounding surfaces. Use a rental jack hammer to break up

the concrete. A hand maul and cold chisel also may be used if the area is not too

large: most concrete basement floors are only 3 to 4" thick.

Grind down high spots if they are small and far apart. A rented concrete grinder

makes quick work of the job. Even larger areas can be ground down, if your ceiling

height is already limited (less than 7 ft.).