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8 min read

Building a Basement Bathroom


8 min read

Building a Basement Bathroom

BathroomBuilding a Basement Bathroom

To turn a basement into a fully functional living space, experts recommend including a bathroom or a half bath. Doing so allows the home’s residents to use the bathroom without having to go up and down the stairs every time. 

It’s all the more important when there’s a bedroom or home office set up below ground level. Once you’ve made up your mind and green-lighted this renovation project, you should really educate yourself on the matter and what it really entails. 

What You Need to Know About Building a Basement Bathroom 

Source: Canva

If your current basement situation doesn’t already include a half bath or bathroom, note that it’ll make the task at hand a bit more complex. It’ll be possible, but definitely more complicated than building a bathroom on the ground floor or a half bath in an area where there’s existing plumbing. 

As a matter of fact, adding a bathroom in your basement involves quite a few additional steps compared to that of a ground-floor bathroom. The reason why is that you’ll need to bring your plumbing downstairs to the basement. 

You’ll also need to install a decent ventilation and dehumidification system, especially given that the basement is notorious for being a moisture-prone area that lacks airflow. 

Hence, on top of meticulously following the step-by-step bathroom building instructions, this project does involve a few additional stages. 

The Different Aspects of Building a Basic Bathroom

Plumbing and Piping

Source: Canva

First off, to build a bathroom, you have to choose a few plumbing fixtures and all the pieces that’ll be connected to the piping, namely:

  • Toilet

  • Bathtub and/or shower

  • Sink

  • Others (washer, bidet)

According to the law, solely certified plumbers can carry out plumbing and piping installations inside residential properties. This part of the project will no doubt be handled in collaboration with a contractor.

Note that we'll be covering the different types of contractors you can work with in this article.


Since it’s a notoriously humid area in which the air tends to accumulate and contaminate, installing a good ventilation system is crucial. 

There are three types of bathroom ventilation systems:

  • Natural ventilation (doors and windows)

  • Spot ventilation (exhaust fan that’s turned on and off, at will)

  • Whole-house ventilation (continuous air renewal)

Here are a few articles to peruse when considering bathroom ventilation systems:

  • What to Consider When Choosing a Bathroom Fan

  • How to Control the Humidity in Your Bathroom


On top of plumbing, a versatile and high-traffic area like a bathroom needs to be well-equipped, electricity-wise. Not only do you need light, but also electrical outlets for the various items you use in the room.

A bathroom’s electrical wiring and placement have a few peculiarities, mainly due to the proximity to water. For safety's sake, the law requires that an expert carry out all electrical work.

Wall Treatments

Source: Canva

When it comes to bathroom walls, most often, paint, (waterproof) wallpaper, or tiles are used.

A few factors to consider:

  • You absolutely must use bathroom-specific paints (check out this article for more information [in French only]).

  • The wallpaper you’re going to choose has to be waterproof and installed properly so that it doesn’t peel due to humidity.

  • Porcelain or ceramic tiles are really good options when it comes to wall coverings.

  • If your budget allows for it, you can also install marble or another type of natural stone on your walls (once again, the whole thing must be properly sealed). 


Any and all bathrooms deserve to be fitted with a storage cabinet and accessories. It’s vital to ensure the area remains tidy, ergonomic, and practical in general. Typically, a bathroom’s storage epicentre is usually the vanity (or sink base). You can also add a closet, shelves, and a linen cabinet. Some homeowners even go as far as hiring a carpenter for custom-made pieces. 

The following article features different vanity models: Bathroom Vanity: How to Choose Your Sink Countertop.


Before making any decisions based solely on aesthetics, a bathroom floor must be safe, easy to clean, and waterproof. As luck will have it, there are numerous products and materials available on the market that meet these standards. 

Here are the best types of flooring for this area in question:

  • Ceramic

  • Porcelain

  • Laminate

  • Vinyl

You’ll find more detailed information in this article: The Best Types of Flooring for Your Bathroom


Source: Canva

Let’s wrap this up with the bathroom’s aesthetic aspect. It’s the perfect finishing touch that will make this space devoted to cleanliness all the more pleasant for all home residents. 

Limits don’t exist nor do specific criteria to adhere to when it comes to decorating a bathroom. Ultimately, what it comes down to is personal taste and needs. Nonetheless, we typically advise homeowners to pay careful attention to lighting and the room’s general brightness.  

Here are some bathroom décor ideas to get you started:

  • 10 Family Bathroom Ideas

  • 10 Examples of Dark Bathrooms

  • 10 Master Bathroom Ideas

Basement Bathroom Requirements

Source: Canva

Installing Proper Ventilation to Reduce Humidity Levels

The entire bathroom has to be properly ventilated, but more so in the basement since airflow is rather restricted in general. Make sure to choose a quality ventilation system, one fitted with a decent dehumidifier. That way, you'll avoid ending up with mould or mildew problems.

Adding Light to a Basement Room

Few and far between are basements flooded with natural light. As a result, you have to pick up the slack with artificial lighting. 

Installing Piping in the Walls and Floors

Now this is the hardest part of building a basement bathroom. In fact, the contractor will likely have to open up your basement walls and dig into the slab to install the necessary piping and drains. This is far more arduous than attempting to carry out this task on an upper floor.

Installing Light Switches and Outlets Wherever Appropriate

There are certain criteria to follow when it comes to installing electrical outlets and light switches in a basement, considering the outlets must be fitted at least 12 inches (30 centimetres) off the finished floor. The light switches have to be positioned at least 48 inches (122 cm) off the finished floor.

Other regulations also apply when it comes to wiring inside walls. A certified electrician will know how to proceed. 

Costs of Building a Basement Bathroom

Source: Canva

Building or renovating a bathroom is a project that requires a significant budget. This is all the more true when it’s located in the basement; the complexity level is all the more real, too.

It’s rather hard to come up with a precise amount that you’ll be putting toward such a project. However, we can still give you some ballpark numbers to prepare you ahead of receiving professional quotes from contractors!

We’re talking about sums that can vary between $4,000 to $30,000. The lower cost is based on cost-effective materials and a very restricted space. On the other hand, if your bathroom is big and spacious and you’d rather select high-end materials, your budget will easily climb up to $30,000, especially for a basement bathroom.

You can use our cost calculator to help you crunch the numbers when the time comes. However, note that the latter won’t take into account any additional costs related to the fact that the bathroom in question will be located in the basement. As such, add an extra $1,000 to the estimated amount.

Do you need a permit to build a basement bathroom?

Source: Canva

Yes, you’ll need to request a building permit for this type of project. It’s also really important that you receive the permit prior to green-lighting the work, otherwise, the authorities at hand will have to shut down the worksite. To know more about it, check out this article (in French only). 

Do you need blueprints or an engineer’s plan to build a basement bathroom?

If your basement bathroom project involves a load-bearing wall whatsoever, you’ll need an architect’s or engineer’s plan. If the project doesn’t revolve around load-bearing walls, you should still have a blueprint since you’ll most likely need one to obtain a permit. In either case, it’ll render the process much easier. 

Can I DIY my basement bathroom building project?

When it comes to such an endeavour, the DIY route isn’t recommended. Right off the bat, it’s much more complex than building a bathroom on an upper floor, and on top of that, the law requires that you hire a certified contractor for all electrical work and plumbing. 

You can always carry out a few of the steps yourself, like painting or setting up certain furniture pieces, however, the result may not be as appealing. As for the rest, it’s best to work with industry experts. 

What kind of contractor should I hire for my basement bathroom building project?

Now that you know that experts are needed for this type of project, you’re probably wondering whom to call. You have plenty of options made available to you:

  • Interior designer: This professional will be able to draw the plans for the room, guide your choices in terms of materials, and even oversee the work if that’s what you want.

  • General contractor: This type of contractor has a permit that allows them to carry out the work, from start to finish. As such, they can offer turnkey services.

  • Specialized contractor: If you’d rather oversee the work yourself, you can hire various specialized contractors (plumbing, electrical, flooring, painting, carpentry, etc.).

To figure out which services best meet your needs, you should still ask yourself what matters most to you: time, money, or both.

If your time is precious and you’re ready and willing to spend a certain amount of money for someone else to take care of the project for you, then the choice will lie between an interior designer and a general contractor (or both in some cases).

However, in terms of money, you could have a bit more leverage over the budget if you hire specialized contractors. However, note that since you most likely have zero construction or renovation experience, the project could take longer than expected and unexpected expenses may arise. So, consider every detail meticulously!

Putting in a Laundry Room in My Basement Bathroom

A lot of homeowners decide to set up a laundry room inside their basement bathroom. If the area in question is big enough to install the required appliances and all the necessary laundry products, it could actually be a worthwhile idea since it’ll mean all the plumbing is in a dedicated area.

Here are some laundry room layout ideas:

  • Laundry Room Design Ideas (in French only)

  • How to Set Up a Laundry Room in Your Home

We also suggest taking a peek at our Bathroom Renovation Checklist, which features a reference document that’ll help you keep track of the work at hand.

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Last modified 2024-02-14

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