Installing a bathroom in your attic can add much-needed space and value to your home. Though it requires careful planning and execution, an attic bath can be a rewarding project for a motivated do-it-yourselfer. In this comprehensive guide, we will walk you through the entire process of installing an attic bathroom from start to finish.
Planning and Designing Your Attic Bathroom
The first step when installing an attic bathroom is proper planning and design. There are several key factors to consider:
Budget
Attic bathrooms often cost $15,000 to $30,000 or more, depending on the specifics of your project. Create a budget and stick to it. Factor in plumbing, electrical work, framing, drywall, flooring, fixtures, ventilation and all finishing details. Be prepared for some contingencies.
Space and Layout
Measure the attic space carefully to determine the optimal layout. Decide which fixtures are essential (toilet, sink, shower) and which you can omit if space is limited (bathtub, vanity). Allow for accessibility and sufficient clearance around fixtures. Consider walk-in showers rather than tub surrounds to save space.
Plumbing
Evaluate existing plumbing lines and plan new drain and vent lines for toilet, sink, and shower/tub. Attics typically allow for plumbing walls and stacked or back-to-back drain and vent lines. Determine if you need a sewage ejection pump.
Electrical and Lighting
Most attic bathrooms require 20 amp circuits for bathroom outlets. Plan lighting, exhaust fans, and heating. Add can lights, skylights, or windows. Make sure wiring meets code. Consider waterproof LED fixtures.
Flooring
Choose flooring that tolerates moisture and unevenness. Tile, vinyl plank, LVT, and seamless linoleum work well. Use backerboard and waterproof underlayment. Avoid broadloom carpet.
Tub or Shower Enclosure
Assess ceiling height and select low-profile tubs if needed. Plan for shower pan installation or use prefabricated units. Choose moisture-resistant shower surrounds like tile, solid surfacing, or fiberglass.
Ventilation
Proper ventilation is essential to prevent mold and mildew. Choose ENERGY STAR exhaust fans sized for room square footage. Run ductwork out through roof or soffits. Include humidity-sensing fans if possible.
Access
Determine how you will access the bathroom. Expand existing stairs or install new pull-down attic stairs or ladders if needed. Minimum stair width is often 36 inches.
Permits and Codes
Check local regulations for required permits, framing, electrical, plumbing, and ventilation codes. Hire professionals as needed to meet requirements.
Once you determine the bathroom specifications, create detailed plans to follow throughout the project.
Preparing the Attic Space
With a design in place, now you are ready to prepare the attic for bathroom installation:
Clear and Clean Attic
Remove all stored items and debris from the attic to clear space for the new bathroom. This also allows you to check the attic framing and access.
Check for Leaks
Inspect the attic carefully for any leaks from the roof or plumbing that may impact the bathroom. Repair leaks before proceeding.
Examine Framing
Look at roof rafters, ceiling joists, and trusses to ensure the framing is adequate to support a bathtub and provide clearance for fixtures. Strengthen framing as needed.
Install Flooring System
Build a subfloor for the bathroom with 2×6 joists and 5/8” plywood sheathing. Use prefabricated trusses if needed to allow for plumbing.
Update Electrical
Have an electrician run updated wiring as necessary to power the bathroom, including new circuits, lights, fans, and outlets.
Once framing and electrical are addressed, your attic is ready for the bathroom installation.
Installing Plumbing for an Attic Bath
One of the most complex parts of adding an attic bathroom is plumbing installation:
Plan Drain and Vent Lines
Map out drain and vent pipe routes from attic to existing home system. Choose shortest routes if possible. Show locations on plans.
Run Drain Pipes
Install new drain lines in planned locations using PVC pipe and water-tight fittings. Add proper venting. Connect to main home drains.
Supply Lines
Run copper, PEX, or CPVC pipes from home water supply to planned fixture locations. Bury supply lines in walls.
Include Plumbing Access
Add access panels in walls and ceilings so supply valves and drains are reachable for repairs.
Install Shut-off Valves
Place shut-off valves near water supply lines so water can be shut off to just the attic bath if needed. Use gate or ball valves.
Pressure and Ejection Pumps
If water pressure is insufficient, add a booster pump on the home’s main water supply line. For sewage, install an ejection pump.
Test Plumbing
Pressurize lines and thoroughly test all drains and water supply without fixtures hooked up. Fix any leaks before moving on.
With rough plumbing complete, you can start framing the bathroom walls and preparing for fixture installation.
Framing and Building Attic Bathroom Walls
Once plumbing is roughed-in, you can frame the bathroom:
Mark Wall Locations
Following the bathroom plans, mark out wall stud locations on the attic floor. Check for plumbing routes.
Install Bottom Plates
Nail pressure-treated 2×4 lumber along the floor to create bottom plates for stud walls. Cut openings for drains.
Construct Wall Framing
Measure and cut 2×4 studs, top plates, and headers as needed. Assemble and erect walls using 16″ on-center stud spacing.
Plumb and Brace Walls
Check walls with a level and plumb bob as you assemble them. Add blocking and diagonal bracing between studs for rigidity.
Add Insulation
Insulate bathroom walls with R13+ fiberglass batts. Use unfaced insulation between bathroom and unconditioned attic.
Install Drywall
Screw 1/2″ water-resistant drywall over studs on bathroom walls and ceiling. Use mold-resistant drywall or cement board on shower/tub walls.
Once framed and sheathed, you can move on to bathroom fixture and finish installation.
Installing Bathroom Fixtures and Finishes
With the bathroom framed and plumbed, it’s time to add fixtures and finishing touches:
Set Plumbing Fixtures
Install the sink, toilet, tub and/or shower according to manufacturer instructions. Use silicone caulk and ensure rock-solid anchoring.
Install Bathroom Vent Fan
Cut an opening for the vent fan ductwork and mount the fan. Run ducts out through roof vents or soffits. Insulate ducts to prevent condensation.
Add Flooring
Lay the flooring as planned, cutting neatly around drains. Use backerboard and waterproofing as needed. caulk edges and seams.
Install Bathroom Vanity
Assemble or set the pre-built vanity in place, leveling and securing it. Seal edges to prevent moisture getting under.
Hang Drywall
Tape and mud drywall seams for walls and ceiling. Apply primer and two finish coats of paint. Use mold-resistant paint.
Add Lighting and Fixtures
Mount the lighting, mirrors, towel bars, TP holder and other fixtures. Ensure proper clearance for doors and fixtures.
Finish Showers and Tubs
Install tub surround kits or shower enclosures as needed. Use fiberglass, acrylic, tile, or solid surface materials. Provide adequate ventilation.
Caulk and Seal
Caulk along all edges, seams, and penetrations with flexible, mildew-resistant silicone. Don’t forget gaps around fixtures, pipes, lights, and vents.
With everything installed, inspect carefully to ensure the bathroom meets code before use.
Common Questions about Attic Bathrooms
Some common questions come up when planning an attic bathroom project:
Does an Attic Bathroom Require Permits?
Most attic bathroom renovations require plumbing, electrical, ventilation, and building permits based on local code. Always check with your city permit office. Licensed pros can pull most needed permits.
How Much Headroom Does an Attic Bathroom Need?
Most building codes require at least 6 ft 8 in of head clearance in the bathroom space at a minimum. Measure from the floor to any rafters, ducts or obstructions overhead.
Can You Install a Bathroom in a Cape Cod House Attic?
Yes, Cape Cod attics can often accommodate bathrooms. You may need to adjust framing, plumbing, and ventilation to work with the roof slope. Choose low-profile toilets and tubs.
What Size Vent Fan is Needed?
Bathroom ventilation codes require fans sized for room square footage. Typically, you need 50 cubic feet per minute (CFM) capacity for baths up to 100 sf, and an extra 1 CFM for each sf beyond that.
Where Does the Plumbing Go?
Drains and supplies can run through framing cavities and directly under the floor into the room below to tie into existing plumbing stacks and drain lines. Flexible piping helps with odd routes.
Conclusion
Adding a well-designed attic bathroom takes careful planning, quality construction, and attention to detail. While challenges exist when working in attic spaces, the result can add invaluable space and appeal to your home. With proper research and preparation, you can successfully tackle an attic bath project and enjoy the benefits for years to come. Just take it step-by-step, get all required permits, and don’t cut corners on the plumbing, ventilation or lighting. Your attic will be transformed into a functional living space for your household to enjoy.