How to Install Baseboard Molding on Uneven Floor

Written by Milan Jara on 4th Jul 2022

Baseboard Molding

Installing baseboards on uneven floors can be a frustrating job. With these simple steps, we teach you how to install baseboard molding on uneven floors.

Many issues can arise when it comes to installing baseboard molding. The most frustrating by far is when you face the issue of how to install basement molding on an uneven floor. As a house settles, floors can frequently become uneven. We will outline how to eliminate your frustration and close gaps on floors that aren’t straight.

Successful baseboard placement generates level lines against the wall at the top of your board. Meanwhile, it maintains its position flush against the floor. When it comes to uneven floors, you must cut the baseboard along the bottom to generate a flush setting.

Making cuts isn’t difficult. With the proper tools, you can make a finished product specifically cut to the floor’s changing levels.

How to Install Baseboard Molding on Uneven Floor

Baseboard Molding

As mentioned, with uneven floors, you may not be able to close gaps easily. Furthermore, some corners on the walls may not be perfectly square either, resulting in increased difficulty in creating a clean angle.

For professional results and to eliminate frustration, follow these simple steps.

Gather Your Tools

Before beginning your work, gather the tools necessary to complete the job. Doing so ensures you have everything you need and saves time as you won’t be searching for tools. Also, it helps you avoid having to run out in the middle of the job because you don’t have what you need.

Here are the supplies you will need:

  • Gloves
  • Shop vacuum
  • Eggshell or semi-gloss paint
  • Sandpaper
  • Carpenter’s level
  • Putty knife
  • Caulking gun
  • Brad nail gun (optional)

You will also need the following materials:

  • Gloss or eggshell paint for baseboards
  • Painter’s tape
  • Paintable caulk
  • Wood or vinyl (flexibility) baseboards

If you are cutting wood baseboards, you will need a carpenter’s square, marking knife or pencil, circular saw setup, or miter box with a saw.

Prepare Your Baseboards

When purchasing the baseboards, you will need 7/16" baseboards made of either wood or polystyrene. This thinness is a better fit for your wall since they are more flexible. It will also be easier to install. Wall base adhesive will also be required to attach your vinyl baseboards.

Measure each of your walls, then mark your baseboard. Using a carpenter’s level, measure your baseboards on uneven floors. You will want your level to be straight. Cut the baseboards using a 90° angle for ends and a 45° angle for bends. You can use either a circular saw or a miter box.

Attach the Baseboard to the Wall

To place your baseboard on uneven floors, use a level to ensure it’s straight. Use a brad nail gun to nail the baseboard into place. You can also use a hammer and nail if you don’t have a nail gun, but nail guns make the work go quicker. For vinyl base molding, use wall base adhesives.

Install Quarter Round Molding (Optional)

If there are only slight gaps in your floors, you can install shoe molding or quarter round. Both are flexible enough to cover small unevenness. Measure the required length and make a mark using a pencil. Cut to 90° or 45° angles.

Take your nail gun and nail the quarter round or shoe molding at 45° angles. You can add a little extra for smaller bends.

You can also shim floor gaps to prevent tilted baseboards using 1/2" scraps of plywood cut into blocks. Tuck them into gaps at two to three feet intervals and install the baseboard over it.

Make sure that it is tight against the floor molding. It is also best to keep nails at the bottom of the base above gaps. They will go through the drywall as opposed to the air.

Fill in Uneven Gaps

If you used a vinyl wall base, you could omit this step because its flexibility can cover the floor’s unevenness.

Grab a paintable caulk and a caulk gun to allow you to attack uneven gaps. Run the caulking in existing gaps. Be sure to wear gloves to protect your hands. Dip one finger in a water bowl. Run a wet finger on your caulk bead to smooth it out.

Wall spackling is recommended since there is no shrinking or crackling. Then, wait for the spackling or caulking to dry. Once dry, use sandpaper to smooth uneven spots.

Paint Your Baseboards

After completing the baseboard installation, use painter’s tape on your walls and floors close to the baseboard. This will provide you with a smooth edge plus an easy paint job. Use eggshell or semi-gloss paint on the baseboards, so you can easily clean them. You can also take the opportunity to remove paint and refinish your baseboard with a new paint job.

Fixing Gaps in Baseboard Corners

Baseboard Corners

If the gaps are in the corners, use wall spackling. Use it carefully and wait for it to dry. Be sure that your caulking has completely dried before using sandpaper to smooth it.

Required Space Between Hardwoods and Baseboards

Very little space is required between a hardwood floor and baseboard. Generally, it needs to be a half-inch gap.

Required Space Between Carpet and Baseboards

Baseboards should be installed between 3/8 inches to one inch from your floor. This will accommodate the underlay and carpet. They tend to be kept level to the bottom edge of the drywall. This is one inch from the floor. This keeps trim and drywall dry from any water leaks or spills.

Once you have completed the cleanup, you will be able to enjoy a professional-looking baseboard and have eliminated most of the frustration. No one will know that there are any imperfections.

However, if you can't easily fix an uneven floor using the previous steps, you may need to reinstall flooring before installing baseboards. You may also need to consult a professional to inspect your house’s foundation.

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