The cost to add a bathroom in Northern Virginia in 2026 runs from $8,000 for a half bath in a basement that is already being finished to $250,000 for a primary suite built as an addition, and the number depends far more on where the bathroom goes than on what is in it. A half bath fitted into existing space on the main floor costs $15,000 to $25,000. A full bathroom in existing space costs $30,000 to $60,000. A basement bathroom costs $8,000 to $15,000 for a half bath and $15,000 to $30,000 for a full one. A bathroom inside a new addition adds $15,000 to $40,000 to the addition, which has its own price. This guide gives the figure for every location, explains what makes one location cheap and another expensive, and covers the sizes, the permits, the timeline and what a new bathroom does for the value of the house. The figures are the ones EA Home Design works to in Fairfax and Loudoun County, and they match our cost guides for bathrooms, basements and additions.
Want a price for adding a bathroom to your house?
Where the plumbing is and where you want the room decide the cost, and that can only be settled by looking at the house. See our bathroom remodeling in Northern Virginia page.
Cost to Add a Bathroom at a Glance (2026)
| Where the bathroom goes | Half bath | Full bath | What decides it |
|---|---|---|---|
| Existing space on the main floor (a closet, under the stairs, part of a mudroom or laundry) | $15,000 to $25,000 | $30,000 to $60,000 | Distance to the drain stack and whether the floor is a slab or framed |
| Existing space on an upper floor (a closet, part of a bedroom, the end of a hall) | $18,000 to $30,000 | $30,000 to $60,000 | Which way the joists run and what is underneath |
| Basement, as part of finishing it | $8,000 to $15,000 | $15,000 to $30,000 | The slab cut and, below the sewer line, an ejector pump |
| Garage being converted | Not usually built alone | $25,000 to $40,000 | The drain line to the main stack, often through the slab |
| Half bath made into a full bath | $15,000 to $30,000 | Finding 12 or more square feet for the shower | |
| Bathroom inside a new addition | $15,000 to $20,000 added to the addition | $15,000 to $40,000 added to the addition | The addition itself runs $250 to $450 per square foot, past $400 with a bathroom in it |
| Bump-out built for a bathroom | $30,000 to $90,000 in all | $15,000 to $50,000 for the structure plus the bathroom | |
| Primary suite addition: bedroom, bathroom and closet | $120,000 to $250,000; up to $300,000 on the main level | Foundation, roof tie in and the size of the suite |
Two things explain almost every number in that table. A bathroom is three pipes: a drain, a vent and a water supply. The supply runs anywhere. The drain has to fall by gravity to the stack and the vent has to rise through the roof, so the closer the new bathroom sits to existing plumbing, and the more directly above or below it, the less it costs. The second is whether the space already exists. A bathroom inside the house needs walls, plumbing and finishes; a bathroom outside it also needs a foundation, a roof and a permit that looks at setbacks.
How Northern Virginia Compares With National Figures
National guides put the cost to add a bathroom anywhere from $20,000 to $90,000 and more, with additions at the top. Fairfax and Loudoun County labor and permit costs run 15 to 25 percent above the national average, and the finish level buyers expect here is higher, so the local figures above sit toward the upper half of the national range for the same scope.
Cost to Add a Half Bath
A half bath, also called a powder room, is a toilet and a sink. It is the cheapest bathroom to add and often the most useful, because a main floor with no bathroom sends every guest upstairs. In existing space on the main floor it costs $15,000 to $25,000 in Northern Virginia: framing, a drain and vent tied into the stack, supply lines, an exhaust fan ducted outside, a circuit with ground fault protection, drywall, tile, a vanity, a toilet, a door and paint. For comparison, remodeling a powder room that already exists runs $10,000 to $20,000; the difference is the new plumbing.
| Half bath dimensions | Size | Notes |
|---|---|---|
| Smallest that works | 3 by 6 feet, about 18 square feet | A toilet at one end and a small sink or a corner sink; the door swings out or slides |
| Comfortable | 3 by 7 or 4 by 5 feet, 20 to 21 square feet | Room for a real vanity and a door that swings in |
| Generous | 5 by 6 feet, 30 square feet | A furniture vanity, and space to turn around |
| Clearance at the toilet | 30 inches wide, 21 inches clear in front | Measured 15 inches each side from the center of the bowl |
| Clearance at the sink | 21 inches clear in front | A pedestal or wall hung sink buys back floor |
| Ceiling | 6 feet 8 inches over the fixtures | Why a bathroom under the stairs puts the toilet at the tall end |
- Under the stairs: the classic place for a main floor half bath, because the space was doing nothing. It needs about 3 by 5 feet of floor with full headroom at the fixtures.
- A coat closet or a pantry: usually close to the kitchen plumbing, which makes the drain short. Our closet conversion guide covers what a closet can become.
- Part of a mudroom or laundry: the drain and supply are already in the room.
- A corner of the garage side of the house: a bump into the garage for a half bath off the mudroom keeps the main floor plan intact.
Cost to Add a Full Bathroom in Existing Space
A full bathroom has a toilet, a sink and a tub or shower, and it needs about 5 by 8 feet, 40 square feet, to hold them. Adding one inside the house costs $30,000 to $60,000 in Northern Virginia. The bottom of that range is a bathroom that backs onto an existing one or sits directly above the kitchen or another bath, with standard fixtures and porcelain tile. The top is a bathroom far from the stack, with a tiled walk-in shower and frameless glass, a double vanity and heated floors. A hall bathroom remodel, for comparison, runs $30,000 to $55,000; adding a new one costs about the same in finishes and more in plumbing and framing.
| Line | Share of a new full bathroom | What it covers |
|---|---|---|
| Plumbing rough and finish | 20 to 25 percent | Drain, vent and supply runs to the stack, the valve, setting the fixtures; the line that moves most with distance |
| Framing, drywall, door and insulation | 10 to 15 percent | New walls, sound insulation, blocking for grab bars and accessories |
| Tile and waterproofing | 20 to 25 percent | Floor, shower or tub surround, the pan and membrane |
| Vanity, top, toilet, tub or shower, glass | 18 to 25 percent | Fixtures and the frameless glass, which runs $2,000 to $5,000 on its own |
| Electrical, lighting and the fan | 8 to 10 percent | A dedicated circuit, ground fault protection, a fan ducted outside at $400 to $1,200 |
| Design, permits and project management | 6 to 10 percent | Drawings, plumbing, electrical and building permits, inspections |
| Paint, trim, accessories and patching next door | 5 to 8 percent | Including the repair to the ceiling below when drains run through it |
What Makes One Location Cheap and Another Expensive
- Distance to the stack. Every foot of drain needs slope, and every fixture moved away from existing plumbing costs $1,500 to $5,000. Back to back with an existing bathroom is the cheapest wall in the house.
- Stacking. A new bathroom directly above or below an existing one, or above the kitchen, shares its stack and its vent. A bathroom over the living room does not, and its drains show up as a soffit in the ceiling below.
- Joist direction. On a framed floor, a drain that runs parallel to the joists fits between them. One that has to cross them is limited by how much of a joist can be drilled, which can decide where the toilet goes.
- Slab or framed floor. A framed floor is opened from below. A slab is cut, trenched and patched, which is why basement and garage bathrooms carry a concrete line.
- The sewer line. Fixtures below the point where the house drain leaves the foundation need a sewage ejector pit and pump, $3,000 to $6,000.
- The vent. Every fixture needs a vent to the roof or to an existing vent. It is the pipe owners forget and plumbers price.
- Hot water and the panel. One more shower can outrun an older water heater, and a 100 amp panel may need upgrading before it takes a new bathroom circuit and a heated floor.
- A window or a fan. A bathroom needs ventilation by code; an interior bathroom gets it from a fan ducted to the outside, not into the attic.
Cost to Add a Bathroom in a Basement
Adding a bathroom to a basement costs $8,000 to $15,000 for a half bath and $15,000 to $30,000 for a full one, on top of the basement finish. The slab is cut for the drains, and where the fixtures sit below the sewer line an ejector pit and pump lift the waste to it, at $3,000 to $6,000 inside the bathroom price. Many Northern Virginia houses built since the 1990s have a basement bathroom rough in, which is three capped pipes in the slab left by the builder; when the rough in is where the plan wants the bathroom, most of the concrete work is already done and the price lands at the bottom of the range.
An upflush toilet, which grinds and pumps waste from a unit that sits on the slab, avoids cutting the concrete. It suits a half bath that is used now and then and a house where the slab cannot be opened; for a full bathroom used every day, a pit and an ejector pump are quieter, last longer and can serve a shower and a bar sink as well. A bathroom on the far side of the basement from the stack means a long trench, so place it under the bathrooms above where the layout allows. Our basement remodel cost guide and basement conversion guide price the level as a whole, and a bedroom beside the bathroom makes a suite at $60,000 to $110,000, as our basement bedroom guide explains. A wet bar on the other side of the bathroom wall shares its drain; see our basement bar ideas.
Cost to Add a Bathroom Upstairs
A second floor bathroom carved from a closet, the end of a hall or part of a large bedroom costs $18,000 to $30,000 as a half bath and $30,000 to $60,000 as a full one. The drains run inside the floor to the stack, so the first question is which way the joists run and the second is what room is below, because that ceiling is opened and repaired. The most common version in a Northern Virginia colonial is a second bathroom for the children at the end of the hall, or a primary bathroom made by taking the smallest bedroom, which costs what a primary bath costs, $60,000 to $120,000, plus the plumbing to reach it. Adding weight matters too: a tiled shower and a cast iron or stone tub may call for the joists under them to be doubled.
Converting a Half Bath to a Full Bath
Adding a shower to a half bath costs $15,000 to $30,000. The toilet and the sink are already there, so the work is finding the space and building the shower: a tiled shower needs at least 32 by 48 inches and is better at 36 by 48, which usually comes from a closet that backs onto the room or from the room next door. The shower needs a 2 inch drain, its own valve, a pan and membrane that are flood tested, and tile to the ceiling; our shower remodel cost guide prices a tiled shower at $12,000 to $25,000 on its own. On the main floor, converting a half bath to a full one is also the first step toward living on one level, and a curbless shower there can qualify for the Virginia Livable Home Tax Credit; our universal design guide covers that plan.
Cost to Add a Bathroom to a Garage
A full bathroom in a garage that is being converted to living space runs $25,000 to $40,000, including the drain line to the main stack, which often goes through the slab. It is rarely built alone: the bathroom is what makes the garage a bedroom suite, at $85,000 to $130,000 for the conversion, or an accessory living unit at $110,000 to $180,000. Our garage conversion guide covers the floor, the insulation and the zoning questions that come with it.
Bathroom Addition Cost: Bump-Outs and New Construction
When there is no room inside the house, the bathroom is built outside it. A bump-out, which extends a room 2 to 8 feet, costs $15,000 to $50,000 for the structure, and the bathroom in it adds $15,000 to $40,000 in plumbing, fixtures and finishes, so a bathroom bump-out lands at $30,000 to $90,000 in all. A bathroom inside a larger addition is priced the same way: the addition runs $250 to $450 per square foot, past $400 once it holds a bathroom, and a half bath adds $15,000 to $20,000 to it. Small additions cost more per square foot than large ones, because the foundation, the roof tie in, the permit and the mobilization are much the same whether the room is 50 square feet or 400.
An addition also answers questions an interior bathroom cannot. It gets a window, and sometimes a skylight. It leaves every existing room the size it was. And it is the only way to add a bathroom to a house whose floor plan has nothing left to give. Our home addition cost guide prices each type of addition, additions 101 compares bump-outs with larger additions, and our guide to planning a home addition covers the sequence.
Primary Suite Addition Cost
A primary suite addition, still often called a master suite addition, is a bedroom, a bathroom and a closet built new. In Northern Virginia it costs $120,000 to $250,000, and $150,000 to $300,000 for a main level suite with a walk-in closet, which is the version built for owners who mean to stay in the house for good. A suite of 400 to 600 square feet is typical. The bathroom is the most expensive room in it per square foot, and the place the suite is most often under planned: a primary bathroom wants a double vanity, a shower of at least 42 by 60 inches, a separate toilet compartment and, if there is a tub, a place for it at a window.
- On the main level, a suite on a new foundation behind or beside the house, at $150,000 to $300,000, three to five months of construction.
- Over the garage, at $100,000 to $200,000, saving the foundation but depending on a structural evaluation of the garage below.
- As part of a second story, at $250,000 to $500,000 for the whole floor, where the suite is one of several rooms.
- As an in-law suite, with a kitchenette, at $120,000 to $250,000 and up.
Design and permits take two to three months before construction starts, and an addition has to meet setback and lot coverage rules that an interior bathroom never meets. In western Loudoun County, houses on well and septic need Health Department sign off before a bedroom is added. Our Loudoun County additions guide covers the local rules, our guide to financing a home addition covers how a project of this size is paid for, and our home additions page shows finished work.
How Long It Takes to Add a Bathroom
| Bathroom | Design and permits | Construction |
|---|---|---|
| Half bath in existing space | 2 to 4 weeks | 2 to 3 weeks |
| Full bath in existing space | 3 to 6 weeks | 3 to 5 weeks |
| Basement bathroom, inside a basement finish | 2 to 4 weeks of design, 1 to 3 weeks of permit review | Part of an 8 to 12 week finish |
| Half bath to full bath | 2 to 4 weeks | 2 to 4 weeks |
| Bathroom bump-out | 6 to 10 weeks | 6 to 10 weeks |
| Primary suite addition | 2 to 3 months | 3 to 5 months |
A new bathroom follows the same sequence as a remodeled one, with framing in front of it: frame, rough plumbing and electrical, rough inspections, insulation and drywall, waterproofing and tile, fixtures, glass, final inspection. Frameless shower glass is measured after the tile is grouted and arrives 10 to 14 days later. Our bathroom remodel timeline walks through each phase.
Do You Need a Permit to Add a Bathroom?
Yes, always. Adding an entirely new bathroom, whether in a basement, an addition or a converted closet, requires permits because it involves new drain, vent and supply lines. Inside the house that means plumbing and electrical permits and usually a building permit for the new walls, with fees of roughly $200 to $600 in Fairfax and Loudoun County. An addition needs a building permit that also reviews setbacks and lot coverage, at $1,000 to $5,000 or more, and in most of eastern Loudoun the homeowners association reviews it first. Fairfax County issues permits for most of the county, Loudoun County for all of Loudoun, and Herndon, the City of Fairfax and Falls Church run their own offices. An unpermitted bathroom is a problem at resale, because the buyer’s inspector and the county records will not agree. Our permit and inspection checklist covers who issues what.
Does Adding a Bathroom Add Value?
It does, and the first added bathroom is worth more than the last. Three additions change how a Northern Virginia house sells. A half bath on a main floor that had none removes an objection every buyer raises. A second full bathroom in a house with one changes who can live there. And a private bathroom for the primary bedroom moves a 1960s or 1970s colonial into the group of houses buyers compare it with. A fourth or fifth bathroom adds convenience but little price. As with any remodel, the rule is to reach the standard of the neighborhood and not pass it; permitted square footage added by an addition raises the appraised value directly, and the additions that return the most are the ones buyers want anyway, primary suites among them. Our guide to remodels that pay off before selling covers what to do, and what not to, in the year before a sale.
How to Keep the Cost of a New Bathroom Down
- Put it next to, above or below existing plumbing. The single biggest saving, and it is free at the design stage.
- Use the builder rough in if the basement has one.
- Choose a shower over a tub in a second or third bathroom, as long as one bathtub stays somewhere in the house.
- Keep it compact. A well planned 5 by 8 bathroom does everything a 7 by 10 does; our bathroom storage guide shows how.
- Porcelain tile and a stock vanity, with the money saved spent on the waterproofing and the fan.
- Build it with something else. A bathroom added during a basement finish, a kitchen remodel or a whole house project shares the plumber, the electrician and the permit; our whole house remodel cost guide shows how much that saves.
- Do not save on the vent, the membrane or the permit. Those are the three that come back.
Frequently Asked Questions
How much does it cost to add a bathroom in Northern Virginia? In 2026, a half bath in existing space costs $15,000 to $25,000 and a full bathroom $30,000 to $60,000. In a basement, a half bath costs $8,000 to $15,000 and a full bath $15,000 to $30,000 on top of the finish. A bathroom in a new addition adds $15,000 to $40,000 to the addition, and a primary suite addition runs $120,000 to $250,000.
How much does it cost to add a half bath? A half bath costs $15,000 to $25,000 in existing space on the main floor of a Northern Virginia house, $8,000 to $15,000 in a basement being finished, and $15,000 to $20,000 when it is added to a new addition. The distance to the drain stack sets the price more than the fixtures do.
What is the cheapest way to add a bathroom? Put it where plumbing already is: back to back with an existing bathroom, directly above or below one, beside the laundry, or on a basement rough in the builder left. A half bath in one of those places is the least expensive bathroom a house can gain.
How much does it cost to add a bathroom in a basement? $15,000 to $30,000 for a full bathroom and $8,000 to $15,000 for a half bath, on top of the basement finish. The slab is cut for the drains, and fixtures below the sewer line need an ejector pit and pump at $3,000 to $6,000, which is included in those figures.
How much does a bathroom addition cost? A bump-out built for a bathroom costs $30,000 to $90,000 in all in Northern Virginia: $15,000 to $50,000 for the structure and $15,000 to $40,000 for the bathroom. Inside a larger addition, a bathroom takes the price past $400 per square foot. A primary suite addition with a bedroom, bathroom and closet costs $120,000 to $250,000.
How small can a half bath be? About 3 by 6 feet, or 18 square feet, with the door swinging out. The toilet needs a space 30 inches wide with 21 inches clear in front, the sink needs 21 inches clear in front, and the ceiling has to be at least 6 feet 8 inches over the fixtures. A full bathroom needs about 5 by 8 feet.
Can I convert a half bath to a full bath? Yes, if 12 or more square feet can be found for a shower, usually from an adjoining closet. It costs $15,000 to $30,000, most of it the tiled shower with its own drain, valve and waterproofing.
Do I need a permit to add a bathroom? Yes. A new bathroom always needs plumbing and electrical permits, and usually a building permit for the walls. Fees run roughly $200 to $600 inside the house and $1,000 to $5,000 or more for an addition in Fairfax and Loudoun County, and an addition must also meet setback and lot coverage rules.
How long does it take to add a bathroom? Two to three weeks of construction for a half bath in existing space and three to five weeks for a full bath, after two to six weeks of design and permits. A bathroom bump-out takes six to ten weeks to build, and a primary suite addition three to five months after two to three months of design and permits.
Does adding a bathroom increase home value? Yes, most of all when it is the first half bath on the main floor, the second full bathroom in the house, or a private bathroom for the primary bedroom. Each of those changes which houses a buyer compares yours with. A fourth or fifth bathroom adds convenience more than price.
Get a Real Number for Your New Bathroom
The cost to add a bathroom comes down to where the plumbing is and where you want the room, and that can only be settled by looking at the house. EA Home Design is a Class A licensed design build firm (license 2705157182) that adds bathrooms in existing space, in basements and in additions across Fairfax and Loudoun County, with the layout drawn in 3D and the price fixed before any wall is opened. See our bathroom remodeling and basement remodeling pages and our case studies, and our bathroom remodel cost guide for the price of the finishes, then book a free in home design consultation or call (703) 687-1818.
