How to Do Plumbing for an Add-on Bathroom

New bathroom addition.

Adding new plumbing to an existing house can be complicated and expensive. After determining where the new bathroom can be located in the home, it is important to determine if your existing plumbing is of sufficient size to allow you to add on additional fixtures. You can usually determine this by discussing your home and showing your provisional floor plan to your local planning department. They will be able to assist you in understanding the size of your existing plumbing system and what permits and issues you are likely to face with your addition.

Things You'll Need

• Tape measure
• 1/4-inch graph paper
• Pencil
• Straight edge
• Tracing paper
• Bathroom template
• Budget
• Permits
• Pry bars
• Sledge hammers
• Sawzall
• Drywall saw

Instructions

1. Measure the room or area that you wish to convert into a new bathroom. Sometimes room can be acquired from closets, bedrooms, porches, laundry rooms or other rooms. Sometimes it is necessary to build on a new addition. Transfer your measurements to your graph paper.

2. Draw the existing house (in the area where the new bathroom will be installed) and show the doors, windows, walls, door swings, light fixtures, light outlets, existing plumbing fixtures and any other feature of the room or rooms. It is important to show adjacent rooms to understand how the new bathroom will fit in or work with those areas. Make sure to add measurements.

3. Place tracing paper over your existing house plan. Draw in the shape of your new bathroom addition. Detail where you want to install fixtures and fittings (like bathtubs, showers, sinks and commodes). If there is existing plumbing near the location of the new bathroom then indicate the location of the plumbing. For example, you may have a bathroom on the floor below your new bathroom location.

4. Calculate a budget for your bathroom project that includes a written estimate from a plumber, electrician, carpenter, drywall and tile person, as well as the cost of all fittings, cabinets and finishes. Add 10 percent for unexpected overages.

5. Take your bathroom plan to your local building department and discuss with their experts the scope of your project. Generally your local building department can determine if the age and location of your home typically included plumbing that could handle the additional load of a new bathroom. You will also be informed of permit costs and other building issues related to your addition.

6. Purchase permits and select a plumber with a good reputation. You may elect to demo the area of the new bathroom yourself to save on costs. This can typically be done with pry bars, hammers, drywall saws and a sawzall. Plumbing an area of the home where no plumbing currently exists typically requires opening up the floor and portions of the ceiling where it is necessary to connect with existing plumbing.

7. Open walls where new plumbing and electricity will be installed. Many new bathroom additions are demolished to the studs so that good access to the wall cavities is provided for the carpenters, plumbers and electricians. It is also necessary to provide an HVAC duct in most bathrooms which may require an additional subcontractor.

8. Rough in the plumbing once demo is complete. Rough-in includes all of the water and drain/waste pipes and a complete testing of these systems to ensure that the new pipes are working correctly. Often shower pans, tubs and commodes are installed during rough-in periods. (Inspection requirements in your area may vary.) Plumbing inspections will often happen once the system is tested.

9. Finish plumbing is when the plumber returns after the cabinets, walls, ceilings and floors have been installed. The plumber will finish with fixtures and fittings so that everything is water tight, sealed and works properly. A final inspection is often required before the project is released.

Tips & Warnings

• Hire a certified and licensed plumber who is recommended by your Better Business Bureau. Check your plumbing and electrical inspections. They should be signed off on the back of the official permit. Take permit questions directly to your building department for clarification. The amount and types of plumbing you will need for your addition will depend on the size and complexity of your new bathroom and the age, size and accessibility of your existing plumbing systems.

• Always look at and read your permits and inspection reports yourself.

References

• Home Owner Net: Bathroom Planning Ideas
• Service Magic: Moving Bathroom Fixtures
• Bob Vila: Basement Bathrooms