According to Remodeling Magazine’s 2011 Cost vs. Value report, one of the top projects that add resale value to a home is adding or remodeling a basement bathroom. That was true in 2011 and holds true even more so today. That said, adding a bathroom is a complicated job. There are building codes to consider, electrical and plumbing issues, insulation, mold control, and more. But, a basement bathroom can provide a family with convenient space for guests or an essential space for a basement bedroom.

Rates vary, but most plumbers will charge anywhere between $1,000 and $3000 to install a bathroom. Costs for the DIYer will be much less. However, if not installed correctly can add up to much, much more in repairs as this is most important to a number of people who are much involved in this.

First things first.You will need to find the main drain because you’ll connect the new drain lines to the existing line under the foundation of your basement. To do this, you’ll need to find the main stack, which is a large pipe that runs into the floor. From here, locate the cleanout plug (typically found on a street-facing wall). Your main drain line will usually run straight from the cleanout plug to the main stack. If you’re on a septic system instead, your line will run from the main stack to the location of the septic system in the drain field. Since sewage must flow down a slope, you’ll need to determine if your plan allows for at least a ¼ inch slope. You don’t want sewage backing up. If your main line doesn’t allow for enough slope, you may need to install a sewage ejection pump.

Next, you’re going to trench the floor. A plain old sledgehammer is the best tool to use to break through to the tie-in point in your main line. Ideally, the trenches (one to the toilet and one to the sink and shower doors) only should be as wide as a spade to dig out chunks of concrete. You will cut into the main line and splice-in a Y-fitting (one for each trench/PVC pipe). The hard part is maintaining your ¼ slope while lining up the pipes.

Some of the headaches can be eliminated by measuring first, buying twice as many fittings as you think you’ll need, purchasing a torpedo level, packing dirt around each section of pipe that’s complete to keep it from shifting, and knowing the distance from the center of the drain (for your toilet, shower, and sink) to the wall.

Keep in mind a toilet will use three-inch or larger drainpipe, and pipes smaller than two inches are allowed under a concrete slab.

Building a plumbing vent system.

Congratulations. You’ve framed your bathroom walls. Now you can start assembling the vent system. A vent system is a whole lot simpler than running drain pipes. Your vent system can be installed below the floor joists and later framed to hide the piping. If you’d rather maintain a certain ceiling height, you can bore holes through the joists. Careful, incorrectly doing so can weaken the joists.

Many basements are set-up to connect the vent system to the laundry sink. Remember, plumbing codes vary by city, so your local rules may require a specific vent size. Check first prior to installing. Without venting, sewage could run through a waste line, creating air pressure and vacuum in the pipe, which can mean sewer gas to flow into your home. Properly venting your basement bathroom is an important step and not worth racing through.

A typical bathroom with a shower or tub, sink, and toilet requires a two-inch vent.

If you are a DIYer, and trying this on your own, you’ll need a few tools to get you through the project, including:

  • cordless drill
  • hammer
  • level
  • Mitre saw
  • 4 in 1 screwdriver
  • reciprocating saw
  • sledgehammer
  • socket/ratchet set
  • tape measure
  • trowel
  • step ladder
  • spade
  • shop vacuum (or broom)
  • rags
  • safety glassesLike mentioned earlier, you’ll also want a torpedo level and pipe-snapper. Both can be rented and will save you time and frustration.

You’ll also need:

  • two 2 x 4s
  • Four-inch plastic and cast iron pipe and fittings
  • concrete (bucket and water)
  • pipe glue
  • band couplings

Whether you decide to hire a professional plumber or do-it-yourself, planning ahead and measuring twice and cutting once are always good rules to keep in mind. Thousands of people tackle plumbing a basement bathroom every year. You can too.