Basement Remodeling:
Important Plumbing Considerations

There are many benefits to finishing or remodeling your basement – increase in property value and added livable area in the home being among them – but there are also some challenges with renovations in the basement that don’t exist with renovations in other areas of the home, particularly if you are adding or relocating a bathroom.

One primary consideration is to recognize that some projects are not DIY, and a basement remodel is one of them. Because the basement forms part of the foundation of the home, it needs to remain secure and sound. When it comes to the structural integrity of your home, you don’t want to run any risks. Hiring professionals will cost more than doing it yourself, but the added cost would be a “peace of mind” line item in the project’s budget.

Plan and Location

The first decision is whether the bathroom will be a half bath or a full bath, as this will have implications on the overall project plan. For a helpful jump-start to this decision, consider its intended use: Will it accompany a guest room in the basement (full bath) or will it be a convenience to avoid running upstairs (half bath)? Careful consideration should be given to this key decision. Retrofitting a tub or shower into a half bath later could be problematic and cause substantial costs.

A good project plan will take into account where to locate (or relocate) the bathroom – which ideally will be in close proximity to the dwelling’s existing water and drain lines. This will ensure both cost effectiveness and aesthetics, especially if the lines will be exposed in the basement ceiling rafters or walls (per the design).

Keep in mind the basement bathroom will involve more than just the plumbing. Much like bathroom renovations in other areas of the home, a bathroom remodel is not a singular endeavor. Because the redo of the bathroom almost always affects walls, floors, ceilings, vents and lighting, other trades will need to be involved. Most bathroom renovations require a general contractor or builder, a plumber, an electrician, an HVAC person, a tiling company, a sheetrock installer and a painter. All these individuals will need to work in a coordinated fashion throughout the project.

Before starting, it would be best to call in the professionals to verify that the plans are appropriate and applicable and that everything meets code and permitting requirements. It would be wise to also check on your local flood plain/level maps to determine whether such plans are prohibited. (In certain low-lying areas in the country, this is the case.)

Unique Plumbing Challenges with Basement Bathrooms

The key challenge with installing or relocating a basement bathroom is getting the running water down and getting the waste back up from the basement.

Water Supply Considerations

Adding a bathroom in the basement will put an additional load on the water supply line, which will create pressure issues throughout the home. (Example: If you open a faucet in the basement, you will reduce the water pressure on the upper floors.) You will need to determine whether the existing lines are sized properly to handle the additional load. If not, increasing the pipe size for the main line at least up to the water heater on the first floor may be necessary.

Drainage Considerations

If the basement bathroom is below the sewer line level, you will need a method of getting the waste up to that point. (Without some mechanism to do this, gravity will keep it from getting there. Upper-level bathrooms have a gravity assist known as “fall” or “slope”; in basements this works against the system.) A sewage ejection system will need to be installed, which will pump the waste up to the proper level for removal. You should also determine whether the existing drain lines are properly vented.

Basement Flooring

Another challenge involves breaking up the floor if you’ll be locating the plumbing lines there. Flooring in basements is usually slab (concrete), which can be a messy and expensive undertaking. In addition, if the drainage lines aren’t deep enough, the ground beneath the floor may also need to be excavated to allow proper installation of the plumbing lines.


Because most basements do not have windows, a high-power ventilation fan to the exterior may need to be installed in order to eliminate moisture.

Other Considerations

As with renovations in other areas, if you live in an area that is prone to freezing in the winter, you should not locate plumbing lines on the exterior walls of the dwelling.

Be sure to check with your insurance agent on whether the finished basement is covered on your policy. (Sometimes it isn’t.) A real estate agent can also give you insights into whether a bedroom in the basement can count as an additional bedroom for the overall house. (Most of the time, the basement bedroom is considered a bonus but not part of the overall bedroom count.)

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