How to Add a Bathroom in a Garage

No matter if you want to add a shower, toilet, or a full bathroom in a garage as part of a remodel project or if you want to make the space more functional, you have a big project on your hands, and you most likely realize this already. The biggest issue you’ll face is drainage, especially if your garage is situated downhill from any sewage tie-in. While no problems are impossible, you may have to adjust your budget accordingly.

1 Small Bathroom
Adding a bathroom in a garage can be a much larger project than you realize, especially if you’re adding it to an existing structure.

Key Considerations for Adding a Bathroom in the Garage

Garages are surprisingly great places to add a bathroom. The reason being is that they’re floor level and they usually have access to your main house’s drainage and piping system. Also, some garages tend to have their frames exposed, and this makes it easier to access the central house wiring setup.

The basic foundation or skeleton of your garage also makes it a nice usable space. If you currently have an attached garage, then a bathroom can be a nice upgrade. It’s also much easier to add to your garage than into the house. The first step to adding a bathroom in a garage is to assess your garage. Give it a good clean and look it over with a critical eye. This will give you an idea on how much space you have to work with.

Step One – Make Sure You Check Your ICC Codes

This is the most important step of adding a bathroom in a garage, and skipping it comes at a huge price. The ICC is short for the International Code Council, and this is a global source of standards and codes and building safety solutions. There are currently 15 international codes, and the one you’re looking for specifically is the International Residential Code. By looking into your local codes, you can confirm whether or not you’re allowed to build in your garage. But, why is this important?

Municipalities try to preserve the community’s nature. Through not allowing these renovations, they ensure that single-family structures can’t turn into multi-family structures. Once you figure out that your local code requirements don’t stop you from adding a bathroom in a garage, you’re good to go. A few of the codes from the IRC that pertain to this project include:

  • Shower Door/Entry Point Space – You need 24 inches of space or more in front of the shower door or entry point.
  • Shower Floor – The shower floor has to have a minimum measurement of 30 by 30 inches.
  • Space in Front of the Toilet – Your toilet needs a minimum of 21 inches of space in front of it.
  • Toilet Bowl Space to the Wall – You need a minimum of 15 inches of space from the center of the toilet bowl to a wall on any side.

If you pass all of these items, it’s now time to assess your garage as a whole. The things you need to concern yourself with are:

  1. Look for any plausible issues first. Plausible issues are things that can affect the space you picked out to add a bathroom in the garage. It could be anything from infestations to water damage.
  2. Double-check the levels of plumbing and electrical services you’ll require to finish the project.
  3. Inspect the flooring, especially where you want to put  your bathroom. Check for any obvious damage and figure out if you’ll need a new subfloor or not.

Step Two – Design and Plan Out Your Bathroom

You’ll have to make some design considerations next. For example, maybe you want to keep the same design aesthetic that you have in your home to make the spaces flow from one to the next if you have an attached garage. Or, maybe you want to go with a very different style. Either way, there are many styles to consider as you pick out your new bathroom’s design and figure out what you need to purchase. A few very popular bathroom design styles include:

  • European style
  • Traditional style
  • Modern contemporary style

Adding a bathroom in the garage can take a lot of money and time to finish. However, it’s worth it to take your time so you can maximize how useful every inch of space is in your bathroom before you start building it. Once you have your design style in place, it’s time to decide to factor in all of the elements you’ll need to install to give yourself a functional bathroom. The main elements to consider include:

  • Flooring
  • Lighting
  • Showers
  • Sinks
  • Toilet bowl
  • Walls and Ceilings

If you have enough space, you can consider adding a vanity or cabinets for storage space. If you plan on installing a bathtub, there are more considerations. Either way, these are the biggest elements to feature in your bathroom in a garage. It’s also a good idea to mark the area where you want to put the bathroom and mark the layout. You can measure it out and use tape for the markers. Once you finish, you can start creating your alcove, and plywood works nice to make the skeleton form. This way, when you move onto the next steps of the project, you will do everything in order. First up is drainage.

2 Bathroom Design
Since there are so many potential designs on the table for your bathroom, you really want to take your time and plan out a functional space that is aesthetically pleasing.

Step Three – Drainage Pipe Installation

This is a larger section that we’ll break down into two parts to make it more manageable, the toilet and the shower. They require different drainage systems with different needs.


For the shower drainage system, you’ll need to have a hole where the drain cover will go. Next, you will attach your drain cover to the drain tailpiece. Finally, you install a rubber gasket on the tailpiece over the drainpipe.

This tailpiece will go to the P-trap before reaching the branch drain. So, now you have to get a hole in your garage. Are there any ways to work around it as the garage floor is most likely concrete and very solid. There are two ways you can get your drainage system in place:

  1. Break through your concrete flooring, install the pipes and everything we touched on above, and seal it off.
  2. Use a raised platform that allows you to run your drainage pipes through the wall. The lines could go to the main branch drain or underground, and this is helpful for people with attached garages.

The drainage system will also include a closet flange that mounts your toilet to the floor, and it also connects the toilet to the drain line. The drain line then connects to the main waste-vent stack.


Since your garage floor is concrete, how do you get your drainage system for the toilet in place? Just like the shower drainage system, you can use the two methods we outlined above, or you can add a type of toilet called the macerating toilet. This is a great option for anyone who doesn’t want to or can’t handle the cost of adding piping. Instead, it utilizes an upflush toilet system, and this system comes with a big container behind the toilet or set into the wall.

Once you get the toilet in place, the toilet will send the waste into the larger container in the back. The container comes with blades that will liquify your toilet waste, and this liquified waste then gets pumped out of the toilet and into the main drain pipe in your garage. As we touched on earlier, this project takes up a lot of time and money. If you don’t have any pipes around your new toilet or shower, you may have to lay more piping or get a macerating toilet if your budget can’t handle the costs.

Plumbing is the central part of this project, and you must commit to it before you get to any other steps for installing your bathroom in a garage. With the plumbing system in place, you can start adding your design elements like plumbing. If you already have pipes running, then you won’t need to worry. All you have to do is add a branch drain that leads to your main pipes in the house.

Step Four – Water Supply Installation

With your plumbing and shower in place, it’s time to consider how you’ll get water into your new bathroom in a garage. The shower supply system usually has the following three elements to worry about:

  • Cold and hot water supplies
  • Shower arm
  • Shower pipe

The shower arm will extend from the wall, and there is an elbow fitting at the top of your shower pipe that will connect the shower pipe to the shower arm. The pipe will run up from the faucet, and it gets fed using hot and cold water supplies. The cold and hot water supplies are in the wall, or you can have them in underground pipes. Most people recommend that you run them through the floor. If you do, during winter, they won’t have an issue with freezing. The freezing can create pressure that forces the pipes to burst.

Another way to prevent any pressure issues is by using three or four-inch pipes. These pipes decrease the pressure loss. This way, your shower will run as expected. However, pipe placement is a huge factor to consider. If you want to run the water pipes through the walls, make sure you have an insulated garage. The same freezing issue will happen if you don’t care for your water supply pipes when you construct them. Another option you have is to add insulated tape around the pipes.

Professionals also recommend that you add a small water heater by your shower. This will help to reduce the process of piping water from the water heater to the main house. However, this may not apply if you have an attached garage and the center house water heater resides in the garage already. If it does, piping it should be an easy process if your water heater is relatively close. If not, get a smaller water heater. Not only will this help to cut costs, but it’s also efficient and economical.

Step Five – Electrical

One of the design elements you may decide to add to your bathroom in a garage is lighting. Electricity will help you easily switch your lights off or on. You could choose to have a vanity light or ceiling light installed. Before we dig into the electrical components, there are a few essential things you have to consider. First, you can’t DIY your electric without having an electrical wiring permit, and there are legal implications if you wire your home without one.

If you don’t have the necessary experience or you don’t have an electrical wiring permit, you want to contact a professional. If you run into any problems and choose to push through, your insurance company won’t cover the costs of any resulting damage. So, it’s critical that you check with your local code agency before you do any electrical work. In some cases, you’ll have to arrange for an inspection before you can do anything. If you are in possession of an electrical wiring permit, chances are, you most likely already know what you’re doing. If not, contact a  professional.

3 Electrical Work
Your electrical is very important but dangerous, so it’s a good idea to enlist the help of a professional when it comes to this part of the project.

Step Six – Installation of the Ventilation System

The International Residential Code requires that you add a window or a decent ventilation system in any form to your bathroom in a garage. Not only does this requirement come from a body of law, but it’s also critical that you have a way to deal with any humidity or smells coming from the bathroom itself.

If you’re someone who spends a decent amount of time in your garage, you’ll need ventilation for the toilet. If you’re using the garage bathroom, the smells may be too much for you in the long run. Adding a window to the garage bathroom is just like adding any standard window to your home. First, you’ll have to make room for it by taking out part of the wall and purchasing window panes and a window panel. But, the installation process is the same.

There are several designs you can choose from, but the most recommended one is awning windows. They open outwards and give you a good amount of privacy. Awning windows can also come with different glass panes, and they don’t have to be transparent if you’re looking for more privacy. Just remember to double-check with the International Residential Codes to ensure that you require this type of ventilation in your bathroom. You don’t want to fall short and get a fine.

Average Cost To Add A Bathroom To A Garage

Families who want to add a bathroom in a garage can expect to pay anywhere from $3,000 to $5,000. However, if you have to install new water and sewer lines, or if they want to build a more luxurious bathroom, the project costs can easily jump thousands to sit around $25,000.

Average Cost To Add Plumbing To Garage

Adding plumbing to your garage can be as affordable as costing $300 for the entire project, or it can go up to $1,800 or higher. It all depends on how you want to install the water and sewage pipes. If it requires an underground installation, you must break your garage floor and run the pipes before you patch the floor again. The distance from the main water and sewer supply lines to the garage also factor in. The longer the distance is, the more your project prices will climb. Adding different fixtures can also increase your overall cost to add a bathroom to a garage.

4 Plumber
Your plumbing could drive up your total project costs very easily, especially if you have to lay pipe because there is currently none under the floor.

General Information

The most practical way for you to install drainage pipes to the bathroom in your garage is by building a raised platform for the toilet and shower. It removes the need to break through your concrete floor and install the drainage pipes. You can run sewage tubes through the wall before you route them underground outside of the house and into your main sewer line.

The drainage pipes have to have a ¼-inch per slope relative to your main sewer connection. A macerating toilet will be necessary if the main sewer line is higher than your sewage tubes or you can’t maintain the required slope for the pipe. Connect the shower to the macerating toilet or install a holding tank to collect any gray water. You have to double-check your local ordinances before doing so.

If you live in a cold climate zone, you should install your water pipes underground and connect them to the toilet and shower. Pipes can freeze if you install them outside the garage unless you live in a hot climate. It’s best to use ¾ inch tubes to help avoid issues with your water pressure. Installing an electrical water heater near the shower makes much more sense than relying fully on the main water heater.  You have to connect the ¾ inch water line to your inlet port on your water heater. You can then connect ½-inch pipes from the shower and toilet to your water heater.

Adding a Toilet To a Garage

Check where you want to place your toilet. The International Residential Code requires you to have a lavatory with a minimum of 21 inches of clearance or space between the leading edge and the wall. It should also have a minimum of 15 inches of allowance from one wall on either side of your toilet’s center point.

Also, consider the space between the back wall and the toilet. You can determine this measurement by adding 12 inches into half of the bowl’s width. The shower floor has to have a minimum area of 30-inches by 30-inches, and your entry point for your shower has to have at least 24-inches of clearance or space in the front.

A Word of Caution Regarding Concrete Floors

If you want to add a bathroom to a garage, your new bathroom addition means that you need the correct plumbing. In these spaces, it’s not uncommon for them not to exist. You now have a cold slab of concrete and a problem. Do you cut through the concrete and put a conventional in-floor drainage and piping system or give up?

Cutting through any concrete floor isn’t something  you should take lightly. Before you rent a jackhammer and take a crack at it yourself or hire a contractor to do it for you, remember the following:

1. Cutting Concrete Will Undermine the Floor’s Structural Integrity

When you cut into a concrete slab, you compromise your garage’s foundational integrity. You might be able to patch the hole back up so it looks aesthetically pleasing, but the floor won’t be as solid as it was before you cut it. Plus, if your home is on a ground that tends to shift or is less solid, like sand, it can settle differently if you cut it.

2. Cutting concrete Can be Very Unpredictable

It’s difficult to know how deep your concrete is and whether it sits on a ledge or just rocks, as well as if it has any tension cables or rebar. You can easily cause huge structural damage if you accidentally cut a tension cable, so it’s common for professional contractors to bring in an X-ray machine to figure out exactly where the cables are before they do anything, and this is another cost.

3. Cutting Concrete Leads to Seepage and Leaks

Once you generate a stress crack in your concrete, ground water and radon penetration are huge issues, and ground water penetration can bring up issues with mold and unwanted moisture problems. It’s important to note that you won’t need a major flood to trigger these issues either. Instead, a higher-than-average water table, due to unusually wet weather, could be the cause.

4. Cutting Concrete is Never 100% Perfect

You may want to cut a circle, rectangle, or square into the floor to bury your sewage ejector and the waste-storage basin, but this perfect shape will eventually crack along the edges and fray outwards in odd directions. Once you create a stress crack, it can extend into the walls or footing.

5. Cutting Concrete Generates Large Amounts of Dust

Breaking through any type of concrete will generate a large amount of dust and noise. The noise steps when you shut the saws and jackhammers down, but the dust won’t go away as quickly. This is because it’s not typical household dust. Instead, you now have thick particulate matter that gets into your central air system, so it can be around for years if you don’t address it correctly.

Adding a Bathroom in a Garage FAQs

5 Adding a Toilet to a Garage FAQs
Even though it’s a common process to add a bathroom in a garage, many people still have questions surrounding this process. We’ve picked out the most common ones for you and answered them below.

1. Is it possible to put a bathroom in a garage?

Yes, it’s possible to put a bathroom in your garage. If you want to add a functional space to this area of your home, this is a great solution. However, this usually isn’t a solo project to take on. You have to check your local IRC codes before you start this project, and some jurisdictions don’t allow you to add bathrooms. You have to check where your home is on the scale. This process takes labor, time, and a decent budget that can top out at around $20,000. This may not be the case for everyone as piping as the main issue. If you don’t have any currently installed, you’ll have to install some.

This is the part of the project that eats up a lot of money. Another part of the installation process that you’ll need to allocate a decent amount of your budget to is wiring. So, double-check with your jurisdiction. You’ll typically have to request an electrical wiring permit, and you’ll have to include some design elements as part of your budget if you want it to match the rest of your home. But, it is possible to put a bathroom in your garage.

2. Can you skip planning permission during the install process?

No, the planning permissions have the law on their side, and you’ll typically have to pay hefty fines or face a form of punishment if you skip them. The final punishment will depend on the local planning commission and the rules they set. The IRC codes come with strict punishments and rules. So, it’s essential for your peace of mind to avoid these fines. You do this by checking and getting planning permission before you start this project.

3. Can you install a bathroom in your detached garage?

Yes, a bathroom can also go into your detached garage. The only problem with this plan is that you won’t have the piping running from the main house, and using this piping will reduce both the overall costs and time of the project. With a detached garage, you have to lay new piping.

4. Can your toilet and shower share a drain?

Yes, your shower, sink, and toilet can all share the same drain, and that drain has to lead to the city sewage drain system. However, they have to be connected in a specific order, and a few basics regarding this process are:

  • The pipe that runs from the bathroom to your city’s sewer line should be four-inches.
  • The toilet connects to this pipe first using a three-inch pipe with a Y joint.
  • The shower drain connects second using a two-inch pipe and a Y joint. The shower will also require a P-trap.
  • The last item you connect is the sink, and you use a P-trap with a 2 or 1 ½-inch pipe.
  • There is a vent pipe that allows air to flow and fill up the vacuum you create whenever you flush out solid matter or water through the drain.

Bottom Line

Now you know that it is possible to install a bathroom in the garage, but this can be a labor-intensive, expensive, and time-consuming project, especially if you want to DIY. Consider calling in the professionals and following your local code agency’s rules to make the project go as smoothly as possible from start to finish.

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