Basement bathrooms are notorious for being wonky. Concrete floors typically slope toward a drain, which isn’t great for bathrooms.
One of the first steps when building a basement bathroom, even before framing and plumbing, is to assess the floor.
Our course, for now, doesn’t have video footage for framing or plumbing the basement bathroom. But we’d be happy to answer those questions and will add those videos once they’re ready.
This bathroom is getting a bathtub and needs the floor to be completely level for the tub to drain properly.
If the floor is more than 1/4″ out of level then address the problem. Anything more than 1/4″ will make it difficult to set the tub, toilet, vanity, and tile work.
Anything less than 1/4″ out of level, for example 1/8″, can be fixed with shims or mortar.
Use a four foot level to check the floor’s slope; place it across the width and length of the floor. In this bathroom the floor was about 1″ out of level, which is bad. So we had to level the entire floor.
Take a 2×4 and find the high point of the floor. This helps establish how high to set concrete screws, which will serve as height indicators for the self leveler.
Add Concrete Screws
Concrete screws, also called Tapcons, can be used as height indicators. We strategically drilled holes in the concrete using a hammer drill and masonry bit.
Without concrete screws, it’s difficult to see how much self leveler to pour over the concrete.
Start this process by drilling a hole in the corner of the bathroom. Then use an impact driver to set the Tapcon height, e.g. 1/4″ off the concrete floor. Continue drilling holes in the floor along the perimeter of the room, setting Tapcons, and checking them with a four foot level (3:20).
It’s only necessary to have about 6 different Tapcons in small bathrooms. We had to use both 2″ and 1-1/4″ Tapcons because the floor was so out of level. In fact, you’ll see Steve react to the terrible floor height in the video (3:33)!
Clean, Prep, and Prime
The next step is to shop vac the floor, seal wood framing, and add a perimeter expansion joint.
Block off the bathtub plumbing using 2x4s (6:10) and add latex caulk to the bottom of all wood plates (6:27). This prevents self leveler from oozing out of the bathroom. Tool latex caulk with a finger to compress it against the concrete floor and wood.
Then wipe down the concrete floor with a damp sponge (7:17) and staple sill plate foam along the wall perimeter (7:35). This foam provides the necessary 1/8″ expansion and contraction joint for the self leveler.
By the way, this is the same foam required underneath wood framing in basements, i.e. lay this foam between concrete floors and wood framing.
Once the self leveler sets up, the foam can be cut using a utility knife. Staple foam to either studs or drywall (8:15).
Finally, apply primer to the concrete floor. Always use primer made by the company who manufactures the self leveler. For example, we used LATICRETE PRIME-N-BOND primer because we used LATICRETE’s NXT self leveler.
Simply paint primer onto the concrete floor using a 3/8″ nap roller (8:50). Primer helps the self leveler bond to concrete floors.
Watch our video for more great tips.
What Could Go Wrong?
This section addresses the Top 5 mistakes that you could make:
- Incorrect Tapcon height: it’ll be hard to know how much self leveler to use
- Skip plumbing trough: self leveler will fill the plumbing trough and cover P-trap
- Forget latex caulk: floor leveler will ooze into adjacent rooms…huge mess
- Omit foam joint: self leveler could crack and cause tile to crack or tent
- Ignore primer: self leveler may not bond to concrete and chip off floor
Tool and Material List
- Prime-N-Bond (Primer)
- Shop Vac
- Sill Foam
- Hammer Tacker
- DeWALT Hammer Drill or
- Ryobi Hammer Drill
- Concrete Screws 1-3/4″
- Concrete Screws 2-1/4″
- Four Foot Level
- Measuring Tape and Utility Knife
- Paint Roller
- Silica Dust Respirator
Questions for Tutors
If you’re reading this you’re the first to view our new course.
How cool is that!!
We’d love your thoughts:
- What did you like and what did you dislike?
- Should we add pictures to clarify certain points?
- Should we do a second video explaining tools and materials?
- Do you want a list of tools and materials, or links to them on Amazon?
- Should we timestamp certain tips for easy reference in the video?
Add your thoughts to the comment section below and we’ll respond.
Jeff and Steve
P.S. Many thanks to Jerome McManus for the great feedback!