Investing time into learning how to install a bathroom fan will pay off when you can enjoy a bathroom without excess humidity and moisture accumulation on the walls and ceiling. And these luxuries don’t come cheap, so you can save by tackling the project yourself. This step-by-step DIY guide will walk you through how to get your bathroom air moving.
Preparing to Install a Bathroom Vent in the Ceiling
Deciding where the fan will go (or where it can go) is the most important groundwork you must do ahead of time. From there, you'll be able to decide on the type of fan and dimensions.
Choosing the right bathroom fan depends on how much air you need to move. You can tell how much air a fan can move by looking at the cubic feet per minute, or CFM. Additionally, the size of your bathroom fan should match the square footage of your bathroom. For example, a 120-square-foot bathroom needs a 120 CFM exhaust fan.
On top of fan size, there are three types of mounting you might choose:
Ceiling-mounted fans
Wall-mounted fans
Remote or inline fans
This guide covers the general steps for installing a ceiling-mounted bathroom fan, but you could modify these steps for a wall-mounted fan if you feel comfortable drilling into your siding. Remote fans go outside of the bathroom, which would require a different set of steps.
Mark Where You Will Install the Exhaust Fan
Before installing an exhaust fan, use a pencil to mark the area you will cut away. You'll want to position your new exhaust fan on a stud in the wall or ceiling, so make sure you mark it on top of at least one.
If you happen to be replacing an old fan or relocating one, you'll need to shut off the power source to the bathroom before beginning. Use a circuit tester to ensure it's off before starting.
Locate Your Reference Point in the Attic
You'll be working on both sides of the ceiling, so head into your attic and clear away any boxes or items that may get in the way. You might also want to set up a light source close to the area if your attic isn't well lit. Before you cut, have reference points for all four corners of the new fan, and mark these with tape or a pencil.
Cut Out the Hole for Your New Vent Fan
Photo: surasak / Adobe Stock
For easy cleanup, consider putting a sheet of plastic or tarp below your work area to catch debris from the ceiling. Using a drywall saw or reciprocating saw, cut away the area to make space for the fan. Gently remove the piece once you cut it out and set it aside or in the trash.
Attach the Fan to the Joist
Use screws to connect the bathroom exhaust fan to the joist using a power drill and screws. Ensure the fan receptacle lines up neatly with the edges of the ceiling. Don't plug in your device just yet.
Cut a Hole in Your Roof for the Vent and Tailpipe
Install your bathroom vent through your roof. Venting the fan into your attic is not a good idea, as it creates an ideal environment for mold or mildew in your air ducts and other areas of your home, which could cause big problems later.
Always practice good roof and ladder safety, such as having someone spot you from the bottom of the ladder when you climb. If this step is out of your wheelhouse, especially since there’s the risk of injury when working on the roof or climbing a ladder, consider hiring a pro.
Measure the hole size needed to get the vent and tailpipe through the attic or side of your home. Mark a circle that's an adequate size for the opening of the vent and tailpipe on the ceiling of the bathroom and the section where you will funnel the pipe outside the home before making any cuts.
Find a reference point on the top of the roof before cutting. Start by drilling a single hole. Peel back the shingles in that area (instead of guessing from the inside and possibly cutting into shingles), then mark the section and make your cuts using a reciprocating saw from inside the attic.
After installing the vent, you'll need to lay the shingles back down around the edges of the hole.
Install the Roof Vent
Pull the roof vent through the hole you've created. Once in place, spread all-weather outdoor caulk around the edges and secure the vent with roof nails if your model has space.
Replace the roof shingles (you'll likely need to cut them to fit around the vent) around the edges. Use roofing cement to seal.
Connect the Wiring for the Bathroom Fan
Turn off power to the fan if you haven’t yet, and use a circuit tester before starting this step. If you feel uncomfortable doing this, ask a local electrician for assistance. Don’t take any chances regarding the safety of yourself and your home.
Remove the fan motor from the receptacle. Run a cable from the fan to the switch if wiring isn't present. Carefully read instructions from your bathroom fan on how to wire the device to the new cable. Most homeowners want their bathroom fan on a separate switch from the lights, which might take additional steps, depending on your existing wiring.
Place the Fan Motor Back Into the Receptacle
Put the fan motor back in the receptacle and secure it, as per the instructions that came with your unit. At this point, you can also plug the fan in.
Mount the Grille
Photo: jivimages / Adobe Stock
Attach the grille to the open section in your bathroom with screws (or clips).
Turn Power On and Test
Turn the circuit back on to power the bathroom. Turn the fan switch on to test it. If it doesn't work and you need to troubleshoot, make sure you turn the power off to the circuit before proceeding. Use a circuit tester to be safe before beginning.
DIY Bathroom Exhaust Installation vs. Hiring a Pro
DIY bathroom fan installation is an extensive project that may not be for everyone. If you don't feel comfortable climbing on the roof, drilling through your ceiling, or working with electrical components—or don’t have the proper tools—you should hire a pro. Installing a bathroom fan costs between $240 and $540.
Bathroom exhaust fans do a great job of removing moisture and humidity, preventing bathroom water from dripping, and reducing odors and air pollutants from your bathroom. If you live in a cold area where opening the window to clear out steam isn't ideal for several months out of the year, installing a bathroom fan might be a great investment.
Does a bathroom fan need to have its own circuit?
Some bathroom fans double up as a bathroom heater, too. If your product does, it will need its own 20-amp circuit. This will change the nature of the project outlined above, and may require the help of a pro. The cost to install a 20-amp circuit is about $700.
What kind of switch do I need for a bathroom exhaust fan?
You might want a separate switch for the fan function in your bathroom, so it doesn't run every time you turn the lights on. Avoid dimmer switches, as that can limit the amount of power to run your fan, especially for larger bathrooms.
Ben is a writer, media strategist, and DIY enthusiast. A former teacher, he's written two books and published articles on major publications like Business Insider and Elite Daily. He lives in Denver.
Ben is a writer, media strategist, and DIY enthusiast. A former teacher, he's written two books and published articles on major publications like Business Insider and Elite Daily. He lives in Denver.
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