Ultimate OC Bathroom Addition Guide

In Orange County and Southern California, a significant percentage of residences built prior to the 1970’s had a limited number of bathrooms. Although this was the norm some decades ago, many homeowners now prefer to have more than one or two bathrooms.

Therefore, it is fairly popular for homeowners to add another bathroom. A bathroom addition increases the comfort and functionality of any home, as well as its market value.

Here at GreatBuildz, we speak with clients every day who are considering a bathroom addition to their home. GreatBuildz is a free service that connects homeowners with reliable, pre-screened home improvement contractors, then provides ongoing project support to ensure a stress-free experience.


In this blog, we’ll share some ideas, costs and tips about adding a bathroom to your home/garage and finding the best contractors for your project.

Related: Estimate the cost of your remodel with our bathroom remodel cost calculator

How much does adding a bathroom to your home cost?

Bathroom Addition Cabinets

The cost of a bathroom addition will depend on several factors. First, it will depend on the location of the bathroom installation… 1) within the existing floor plan of the home (for example, a closet), 2) within the garage, or 3) as a brand-new structure to enlarge the footprint of the residence.

Adding a bathroom inside your home could cost between $30,000 and $40,000, depending on factors such as the location of the plumbing pipes. It may cost an additional $5,000 to $20,000 to install a bathroom in the garage because the space must be ‘completed’ with drywall, lighting, and HVAC to resemble an inside room. Building a new bathroom extension outside the footprint of your current home will cost between $50,000 and $100,000.

The cost of a brand-new bathroom will also depend on its size and amenities. Obviously, a half-bath with just a toilet and sink will cost less than a complete bathroom with a tub or shower. A lavish master bathroom will incur the greatest expense.

Although the bathroom addition cost estimates provided above might serve as a starting point for budgeting, the best way to obtain exact costs is to discuss your project and designs with a few qualified general contractors.

What is the value added by a bathroom addition?

The value of your home will always increase if you add a bathroom. On the west coast of the United States, the average return on a bathroom addition is approximately 67%, but this figure can vary substantially depending on the size and kind of bathroom you are adding.

Related: Bathroom Renovation Necessities – 7 Things to Know for Your Next Project

Options and Sizes for Bathroom Additions

Bathtub Addition

Half-bath (powder room): If you need an additional bathroom for guests so they don’t have to share with family members, a half-bath is an excellent choice. It consists only of a toilet and a vanity/sink, saving you the cost of a shower or bathtub. It is sometimes possible to make a half-bath from a closet or other small interior space, as a half-bath can be rather compact and fit into as little as 25 square feet.

Full bath (or three-quarter bath): This sort of bathroom has a shower or shower/tub combination and is suitable for use by the home’s residents, especially if too many people are already sharing a single bathroom (a three-quarters bath has no tub, only a shower). If the homeowner desires double sinks, linen space, etc., the bathroom may need to be larger than the typical 40 square feet (8 feet long by 5 feet across).

Clearly, a master bathroom must be adjacent to the master bedroom within a suite that includes the bedroom, bathroom, and walk-in closet. The size can range from a basic 40-square-foot layout to 200 square feet or more, depending on what you wish to add. Typically, a master bathroom features two vanities or sinks, a separate tub and shower, and a toilet. It may also contain a linen cabinet or a complete closet.

What factors influence the price of a bathroom addition?

cost of adding bathroom

Because they are fixed costs, there are certain elements and expenses in a bathroom addition over which you have no control. These include a new foundation, wall frame, drywall, roof, electrical wiring, plumbing lines, insulation, stucco, etc. These are the categories that do not vary whether you are building on a budget or spending lavishly.

Alternately, there are a variety of elements that go into a new bathroom addition that affect your prices and budget based on your choices, as illustrated by the following examples:

– Windows: Having a window (or skylight) in your bathroom is not required, but it will undoubtedly make the area lighter and brighter. The prices of windows vary significantly depending on your pick. In addition, you should purchase windows that match the existing windows in your home. A typical window may cost between $500 and $1,500, including installation.

Bathroom Flooring: The price will vary dramatically based on whether you choose a less expensive material, such as ceramic tile or vinyl plank, or a more expensive option, such as marble, stone, or exotic tile. Luxury materials may cost as much as $40 per square foot per-square-foot for bathroom flooring, with a base price of $10 per square foot per-square-foot (including installation).

– Lighting: Recessed lights are relatively inexpensive, costing between $100 and $200 per fitted light. Other lighting expenses can vary depending on the fixtures you select, ranging from less than $100 to… quite costly.

Modern Bathroom Design

Tile is labor-intensive and hence expensive to install, regardless of the design you choose for your shower. Selecting a cheap porcelain tile that comes in larger pieces will help you save money. Larger tiles require less time to install. In contrast, if you choose a pricey tile, especially in a small format, the price will increase significantly. The cost of tile materials can range from as little as $1 per square foot to well over $20 per square foot for materials like glass and marble. Add $10 to $20 per square foot for installation.

Bathroom Fixtures: Items such as faucets and shower hardware are available at a reasonable price from retailers such as Lowes and are often available in basic styles and finishes such as chrome or brushed nickel. At establishments such as Ferguson, you will have to pay substantially more for upscale designs and finishes such as gold or matte black.

– Bathroom Cabinets & Vanities. You can find bathroom vanities in common sizes and designs at major home improvement retailers and on the Internet. These range in price from $150 to $1,000 and are suitable for a half-bath, powder room, or full-bath of standard size. For a large or master bathroom, you will likely require a double vanity with two sinks ranging in size from 60″ to 72″ and priced between $1,000 and $3,000, inclusive of the vanity cabinet, countertop, and sinks.

Alternatively, if you need a custom vanity in a particular size or additional bathroom cabinetry, your contractor will need to have it custom-built. In addition, you can select a custom countertop and a variety of sink alternatives. In this instance, you may anticipate spending a minimum of $2,000 and possibly up to $5,000 or more.

– Plumbing: Keep in mind that connecting the new bathroom to the existing water and plumbing pipes is one of the most expensive aspects of adding a bathroom in Los Angeles or Southern California. Having these in close proximity to your new bathroom location will undoubtedly reduce expenses.

The most difficult plumbing involves connecting the sewer/waste lines from your new bathroom to the existing pipes in your residence. The precise location of these lines depends on the type of foundation you have. Under a home with a raised foundation and crawlspace, these lines are reasonably accessible. Alternatively, if you have a slab foundation, the pipes are contained within the concrete slab. To gain access to these, the concrete slab must be cut, which raises the expense of the job.

For a full cost breakdown, check out my blog about bathroom remodeling costs.

What is the procedure for adding a bathroom?

Bathroom Fixture

After researching pricing and selecting how you will pay for the expansion, the following step is to contact several contractors. The contractor will likely introduce you to an architect with whom you can negotiate the building designs’ expenses (about $8,000 to $15,000). The contractor will probably discuss the exact cost of the project, the timing of work, and other construction-related factors with you.

It could take up to two months for the architect to prepare a complete set of building plans and get them approved by your building department’s plan review procedure. Once work begins, it will likely take less than two months to complete.

As opposed to a home remodel, a bathroom addition is usually performed “outside” of your existing living space, so you won’t have to deal with the dust and inconvenience of living without a bathroom.

A reputable contractor can provide you with an approximate estimate of the cost of a bathroom addition based on their past experience with comparable projects, but they may tell you that they cannot provide an accurate price until your plans are finalized.

How can I locate a reputable bathroom addition contractor?

Modern Sink

Finding an excellent, dependable contractor is not always simple. In Orange County alone, there are over 5,000 licensed general contractors to choose from when searching for a bathroom remodeler, making it difficult to distinguish between the good and the bad. Asking friends, neighbors, or dependable coworkers for referrals to reputable bathroom contractors is the most effective way to find qualified professionals. If you seek recommendations on social media, you should only believe your “real world” friends’ suggestions. People you do not know directly are frequently biased (they’ll promote their brother’s construction company, etc.).

Consider using a firm that performs extensive contractor screening and provides personalized introductions to good general contractors if you do not have enough solid referrals from friends and family (www.GreatBuildz.com or similar). Do not randomly select a home contractor from a flyer in your junk mail or a national contractor directory website. Refer to my blog for information on how to locate and hire the best contractors.

When it comes to planning and coordinating a bathroom addition to your home, you shouldn’t have to go it alone – GreatBuildz can help simplify your renovation experience.

GreatBuildz is a free service that connects homeowners in Los Angeles, Orange County, Ventura County, and San Diego with reliable, thoroughly screened general contractors and provides project support from start to finish.


Call now (818.839.6855) to chat with a real person about your next renovation project or visit our website for more information: www.greatbuildz.com.

Hi, we're Paul and Jon - Co-Founders of GreatBuildz. We believe everyone deserves to find a great contractor, have a stress-free renovation, and enjoy their beautiful new space. There are so many contractors out there and it's often hard to tell the good from the bad... until it's too late. We started our company to help simplify your contractor search and help you have a stress-free renovation experience. We're always available to help, no matter where you are in the process. Click here to learn more about our story.

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