Beyond Plumbing and Permits: 6 Things to Consider When Adding a New Bathroom

C.E. Larusso
Written by C.E. Larusso
Updated September 30, 2021
Mother helping daughter brushing teeth in bathroom
Kate_sept2004/E+ via Getty Images

What you need to know before you pick out the perfect clawfoot tub and start tearing down walls

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Having a bathroom space to call your own feels luxurious; you don’t have to hide all your toiletries when guests come over, and you don’t have to wait for your kid to finish showering up after soccer practice when you’re rushing out for the night shift. A bathroom addition not only adds to the comfort level of your home, but also increases its resale value. If you’re getting ready to give your kids or aging parents their own space to wash up, read this list of six considerations to make sure you’ve got all your ducks in a row before construction begins.

1. The Cost

The average cost for a bathroom addition is $15,000, though that only applies to an existing space; if you need to build out, the price jumps, running from $20,000 to $50,000, or even higher for builds with luxury appliances, stoneware, and the like. You’ll also need to pay for an electrician and plumber unless you feel confident handling those kinds of tasks yourself, and that will run you $50 per hour. Finally, there might be permit costs associated with a bathroom addition, so check with a local expert to make sure they will complete your remodel in line with local regulation.

2. The Purpose

Why do you want another bathroom? There are many potential reasons, but determine what they are and prioritize them so you can strategize your design accordingly. If your reason is to get a great ROI (typically, bathroom additions recoup 80% of the remodeling expense), make sure you pay attention to the bathroom trends and which features will increase your resale value. If you’re just looking to get your teenage daughter her own space to practice makeup for hours on end, that will likely affect where you want to build in your home.

3. The Location

Bathroom interior with hallway view
Irina88w/iStock via Getty Images

You may already have a small bathroom idea for your bustling home, but if not, consider these areas.


One way to make your primary bedroom feel more luxurious and convenient is to add a primary bathroom. You can even carve out a small portion of the room into a washroom: a 3-foot-by 6-foot area can accommodate a sink and toilet, and something larger at 3 feet by 8 feet should work with a shower enclosure. You can also consider converting an existing walk-in closet into your new bathroom.


If there’s an unused end of a hallway with at least 30 or 40 square feet, you should have enough space to design an additional bathroom.

Laundry Room

Find ways to reduce your current footprint in the laundry room by reorganizing, adding shelves, and buying a stackable washer and dryer unit to find room for your bathroom. A big benefit of building in this space is that you’ll already have plumbing hookups needed for the conversion.


Your average sink, tub, and toilet will only need about 5 feet by 6 feet, so take the measurements and see if you can turn one into two.

Below a Staircase

You’ll need to make sure you have enough headspace, but a bathroom can often fit neatly underneath your stairwell.

4. The Plumbing

It’s always easier to install a bathroom where plumbing and electrical lines exist, such as next to another bathroom, a laundry room, or the kitchen. If your current plumbing and electrical system aren’t up to code, you may find yourself overhauling the entire thing. And if you’re running on a septic tank, make sure it can handle the addition of another bathroom, or you may face a very pricey upgrade. Hire a local plumber to get an idea of where it would be smartest to place your addition.

5. The Permits

Before you start tearing down walls, you should read building codes and regulations in your area related to changing your home’s floor plan. Every state and municipality has different rules, so you’ll want to make sure you have the right permissions and permits in order. In addition, the city might require you to use certain types of pipes or install windows of a specific size, which could impact the location of your washroom.

6. The Ventilation

As noted above, your municipality might require windows, but even if they don’t, they’re a good idea. A bathroom is a high-moisture area that requires flowing air to prevent mold and mildew from growing, so try and build your bathroom so it has an exterior wall for a window or has access to the roof where you can install a skylight.

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