Bathroom in Basement

Installing a Basement Bathroom has a Number of Unique Challenges

By Mark J. Donovan

The installation of a bathroom in a basement can be very challenging, particularly if it is a retrofit job or part of a basement finishing project. Installing a bathroom in a basement typically involves cutting the basement slab and having to run drain pipes. Cutting a basement concrete slab is hard, loud and dusty work. Years ago I installed a basement bathroom as part of a basement finishing project and wound up spreading dust throughout the entire house when cutting the concrete slab, even though I had sealed off the area with plastic and created a low pressure with a fan to vent the dust outdoors.

If your basement bathroom plans involve tying it into a private septic system a pump up ejector system also needs to be installed. This involves cutting approximately a 3’x3’ hole in the concrete slab and then digging a large hole below the concrete slab grade to insert a 32 gallon holding tank.

Inside the tank is a pump-up ejector system that ties into the main drain and vent stack. Also the drain pipes from the toilet, sink, and tub/shower area need to be tied into the holding tank.

After the inspection has been completed, the concrete basement slab needs to be filled in with concrete and floated to create a perfectly smooth basement floor. I’ve personally installed pump-up ejector systems myself, and suffice it to say, it’s not easy. There’s a lot of work involved.

As an alternative to cutting the concrete floor you may be able to frame in a step up floor for the bathroom so that you can run drain pipes without having to cut into the concrete slab. Some smaller and flat pump-up ejector systems can reside in the step up framed floor area.

Building a bathroom in a basement.

The only issue with this type of basement bathroom is that there may be inadequate headroom to go this route. Also, stepping up into a bathroom is less appealing to most homeowners.

Bathrooms in basements typically require extra framing to tie in walls to the upper level floor joists. In addition, if a tub and/or soffit lighting is in your basement bathroom plans then additional framing is required.

Often basement bathrooms include custom ceramic tile showers, and shower pans. Even though the shower is on a slab, a pre-sloped mortar shower pan is still required to ensure adequate slope to the shower drain area. DIY homeowners frequently end up with shower drain problems because they don’t realize this.

Ceramic tiled floors work extremely well in basement bathrooms. The tiles can be installed directly onto the concrete floor and there is less of a concern for mold and mildew growth. Plus they are very easy to maintain.

Installing a bathroom cabinet vanity in a basement bathroom can also be challenging. Often basement floors are not level.

Bathroom Remodeling Bid Sheet

Consequently the floor may need to be first leveled with a self leveling compound, or alternatively the bottom of the bathroom vanity may need to be scribed to blend it into the floor evenly and ensure a level bathroom countertop.

Often bathrooms in basements lack natural light, so it’s important to include plenty of electrical lighting in them. Make sure to include both general and spot lighting. Also make sure there is a bathroom ceiling fan and that it is vented to the outside. Basement bathrooms have the tendency to fog up very easily due to the cooler temperatures often found in basements.

Finally, if you have a private septic system, check with your local building inspector before installing a bathroom in a basement. Besides needing to pull permits, you may need to modify your septic system to install one. Pump-up ejector systems may require a different type of holding tank with an additional chamber.

For help on your bathroom remodeling project, see my Bathroom Remodeling Bid Sheet. The Bathroom Remodeling Bid Sheet provides a request for quote checklist section that you can provide to prospective bathroom remodeling contractors. It also includes a comprehensive bathroom remodeling cost breakdown table, in Microsoft Excel format, that allows the contractor to include his projected remodeling costs for every phase of the project.

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