How To Install A Bathroom Fan On First Floor (14 Step Guide)

Do you want to learn how to install a bathroom exhaust fan on the 1st level of a home?

A low profile bath fan with a thin housing can make this type of installation easier.

In this guide, I will go over...

  • Installing the flex vent to the exterior
  • Wiring the bath fan
  • Securing the housing to ceiling joists

Let's get started with this guide!

how to install a bathroom exhaust fan on first floor

How To Install Bath Fans On The First Floor?

Installing a new bathroom fan on the first floor of a home can be a big challenge if there isn't an existing bathroom fan and duct. I invite you to read my guide on replacing an existing bathroom fan without attic access if you already have an old bath fan.

The first main step in installing a bath fan on the first floor is to determine the placement of your bath fan on the ceiling, and to choose where it should exhaust on the outside. You will need to route a flex duct from the bathroom to the exterior wall. You can use either a reciprocating saw or hole saw to cut into the exterior wall. Afterwards you will need to secure the duct to an exterior vent hood.

Besides the ducting, the other main challenge will be getting Romex wiring from the electrical panel box to the bathroom. Once you have routed the duct and the wiring, you can secure these items to the bathroom fan housing after you have cut into the drywall.

To read the details of each step, keep scrolling...

Read Also: What Are The Best Delta Bathroom Fans?

Step 1 - Determine Location of Bath Fan

Homeowners first need to make a decision about where to put the bath fan.

Ideally the fan should go in the middle of the bathroom and at the highest ceiling location in order to exhaust the most air. If you want to install the fan above a shower or tub, it should be rated for that location and will need to be connected to a GFCI circuit.

You should also determine the location of the exterior vent hood or where the flex duct will terminate on the outside. It needs to vent to the outside, but you should try to keep it away from windows and other vent terminations.

Step 2 - Route Wiring From Panel Box

Since this is a new bath fan and not a replacement, Romex wiring will have to be routed from the panel box to the bathroom.

If there is existing drywall, you will have to fish the wiring through the wall cavity using fish tape, and you may need a long flexible drill extension to cut small holes through joists.

With the wiring pulled through the bathroom, make sure there is enough length, and cut the wiring with room to spare.

An electrician is recommended for the installation of wiring.

Read Also: What Is The Cost To Install Bathroom Exhaust Fans?

Step 3 - Route Flex Duct To Outside

After you have the wiring ready to be connected, you should work on pulling the flex duct through the ceiling and to the exterior.

If there the home in unfinished (no drywall) then it should be pretty easy to get it to where you want it to go. If there is drywall, you will have to use whatever means to get it to the exterior wall such as with fish tape --- similar to pulling electrical wiring. You may also need to cut an access hole next to the exterior wall in order to get the flex duct to the proper location.

If the ceiling is open (no drywall), then it is recommended to support the flex duct every few feet with straps that are fasted to the joists.

Bathroom fan ducting should never be terminated inside a wall cavity or into the attic. The moisture pushed into an enclosed space can cause wood deterioration and even mold growth.

how to install a bathroom exhaust fan on first floor (1)

Step 4 - Cut Exterior Wall Hole

Once you have routed the flex duct to an exterior wall, you will need to cut a hole so you can install the exterior vent hood to the duct. The exterior wall hole should always be slightly larger than the flex duct diameter.

Probably the easiest method is to use a 3, 4, or 5 inch hole saw coupled with a cordless drill. However, using a reciprocating saw can also work well.

Read Also: How To Install A Bathroom Fan Roof Vent?

Step 5 - Connect Duct To Hood

Once you have cut an exterior wall hole, you will need to connect the flex duct to the vent hood adapter.

The vent hood cover should have a metal collar that you can pull the flex duct over. You can secure the flex duct using either a zip tie or foil tape.

Step 6 - Install Vent Hood Cover

After the duct is connected to the vent hood, you will need to screw the vent hood to the exterior wall.

Installing silicone caulking around the vend hood is also recommended.

Step 7 - Cut Drywall Hole

After the drywall has been installed or if it already exists, you will need to cut an exploratory hole roughly in the location where you plan on installing the fan. A keyhole or drywall saw is a small handheld tool that can easily cut drywall.

Once the exploratory hole has been cut, you can peek in the hole to feel for the joists, the wiring, and the duct. Cut a rectangular hole to fit your bath fan housing, but make it slightly larger to accommodate the fan flanges on the bottom.

Read Also: What Are The Top Bathroom Window Exhaust Fans?

Step 8 - Dry Fit The Housing

Before you connect the duct or wiring to the fan housing, make sure that it fits properly.

You may need to use the keyhole saw to make the hole slightly larger.

You may also need to install a wood support to the ceiling joist for it to fit properly.

Step 9 - Connect Duct To Housing Adapter

It is usually easier to connect the duct to the bath fan first prior to doing the wiring.

Bring the bath fan housing close to the ceiling, and pull down the flex duct. If you have a helper holding the bath fan, it will be much easier. Pull the flex duct over the bath fan adapter, and secure it with foil tape or with a plastic zip tie.

Step 10 - Pull Wiring Through Housing

Before you screw the housing onto the ceiling joists, you will need to do the wiring.

Prior to wiring the bath fan, it is recommended to install a plastic grommet on the housing which will help protect the wiring from abrasion on the metal edges.

Once you know the grommet is installed, you can put the entire housing into the ceiling hole, and then take the Romex cable which is non-metallic sheathed cable and pull it through the grommet.

Read Also: How Much Electricity Do Bathroom Fans Use?

Step 11 - Connect Wiring

With the house power off at the panel box, it is time to connect the wiring.

There should be a black, white, and green or bare copper wire. Connect the black to black, the white to white, and the green wire to the ground screw. You can use either wire nuts or quick connects.

After connecting wiring, install the wiring box over the wire nuts.

Step 12 - Secure Housing To Joists

After connecting the duct and the wiring, you can fasten the bath fan steel housing to the ceiling joists.

Hang the housing flush with the ceiling, and nail or screw it to the joists. After securing the housing, install the fan motor itself to the housing. There may be metal clips to secure the fan motor or you may need to drill a few screws.

Step 13 - Install The Fan Cover

After securing the housing and fan motor, you can install the bath fan cover.

Most bathroom exhaust fan covers will have metal clips that you will have to squeeze and insert into the fan housing.

Read Also: What Are The Top Ventless Bathroom Exhaust Fans For Half Baths?

Step 14 - Power The Fan

It is time to plug in the bath fan and test it.

If there is a housing plug, you should plug the fan motor into it. 

Otherwise, you will need to flip the breaker to on, and flip the wall switch to see if it works.

Final Thoughts

Installing a new bathroom fan (rather than replacing) is a job that isn't for the faint of heart. Routing ducting and wiring to the bathroom can be a lot of work. If it is new construction, and there isn't any drywall up yet, it will make the job significantly easier.

But if you have an old house that never had a bath fan, it will be a challenge.

You can also make a bathroom fan installation easier if you buy a bath fan that is described as "low profile" which means it has a thin housing that gives you more room in the ceiling cavity.

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Arie Van Tuijl

Arie Van Tuijl

I am a licensed home inspector in two U.S. states and the founder of Home Inspector Secrets. After performing hundreds of inspections, and seeing thousands of house defects, I realized people would love to have an online resource dedicated to home maintenance. I write detailed home guides and product reviews sprinkled with inspection tips. You can read my bio here.

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Home Inspector Secrets is an online resource for owners, buyers, and sellers to understand all aspects of home maintenance. We have detailed home guides, product reviews, inspection advice, and much more.