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Permit Requirements For Installing a Bathroom Fan

If you are starting a remodel or designing a new bathroom, you will likely need to consider installing an exhaust fan. Before you begin your project, it is necessary to make note of the materials you will need for the installation of the exhaust fan, including a building permit.

This article outlines everything you need to know before applying for a building permit and embarking on your project.

As a general rule, a building permit is required for the installation of a new bathroom exhaust fan. No permit is needed when an existing exhaust fan is replaced with a new one.

Do I Need a Permit to Install a Bathroom Fan?

Electrical circuit renovations typically require a building permit, which means you will need a building permit to properly wire/install a new exhaust fan.

While installing a bathroom fan may seem like a minor job, the need for a permit is not to tie you up in governmental red tape. Bathroom fan installations involve electrical wiring and ensuring this is monitored and inspected is vital to safety.

However, if no re-wiring or electrical maintenance is needed to install your new fan, in other words, you are simply unplugging one fan and plugging in a new one, then you may not need to obtain a permit.

As regulations pertaining to whether or not you need a building permit to install an exhaust fan in your bathroom vary based on location, you should contact your local building department regarding their policies and guidelines. They can also assist you with other/follow-up permit-related questions.

Listed below are examples of permit guidelines from two different locations in the US.

San Diego, California

Here, homeowners and contractors have the option to obtain something known as a “simple permit“. This is a mechanical, electrical, and plumbing permit that is granted for simple installations, including the installation of a bathroom exhaust fan.

Superior, Wisconsin

A permit is required in this city when upgrading/adding electrical circuits, fixtures, equipment, and device (Permit Guidelines). Installing a bathroom fan falls into this category, which means a permit is required prior to the installation of a bathroom fan in Superior. Furthermore, it means that if you have an existing fan and want to replace it with a more feature-heavy option, you will need a permit.

How Do I Apply for a Permit?

To apply for a building permit, first, contact your local building office and provide details regarding your project. They will be able to tell you based on the details you provide whether or not it is necessary for you to obtain a permit and which permit you to need to apply for.

If a permit is required for installation, you will be given an application form that outlines requirements, additional permits, documents, or other information necessary to obtain a building permit.

After completing the application for the building permit, submit the application to the indicated address or email address and pay any required fees. You will need to apply for a permit before you begin the installation process.

Can Someone Apply on My Behalf?

If you hire a contractor to install your appliance, they will usually handle the application for a building permit themselves. However, if you plan to perform the installation by yourself without the aid of a contractor, you as the homeowner will need to apply for a permit.

Continue reading to learn what information the individuals issuing the permit will want to know about your project, various costs associated with receiving an installation permit, the typical timeline for a permit to be approved, and who is authorized to install your exhaust fan.

What Will They Want to Know About the Installation?

To receive a building permit, you will be required to provide architectural, structural, mechanical, and electrical information pertaining to your bathroom. Below is a list outlining the information that those who review your application for a permit will likely want to know.


  • Floor plan
  • Site plan
  • Elevation details
  • Details and sections of the bathroom
  • Materials being used in installation/material of fan


  • Connections/anchorage
  • Any beams/columns located in bathroom
  • Details pertaining to bathroom floor, ceiling, and walls


  • Heating/cooling information
  • Smoke control and evacuation systems in place
  • Bathroom duct layout


  • Outlets
  • Switches
  • Lights

How Much Will an Installation Permit Cost?

The cost of a building permit can vary depending on the project. Building permit cost can be determined based on a flat rate, the number of square feet, or the value of the construction project.

Building permits can usually be paid using cash or a check sent to the recipient by mail. Additionally, they are often able to be paid online using a credit/debit card. Below is a table displaying the average cost of a permit for a variety of renovation projects.

ProjectAverage Cost
Building Home$1,000-$3,000
General Construction$500-$2,000
Room Addition$200-$600
Water Heater$25-$250
Bathroom Remodel$150-$600
Kitchen Remodel$500-$1,500
Basement Finishing$200-$1,000

Typical Permit Approval Timeline

Typically, it takes an average of two weeks for a residential building permit to be approved. Permits for smaller projects may be granted as early as the same day that the application has been submitted.

Who Can Install My Bathroom Fan?

Electricians typically handle bathroom fan installations. If you need any new ductwork in the bathroom, it is recommended to hire a plumber or HVAC specialist.

It is important to note that if you obtain the required permit(s), you as the homeowner are also able to install the bathroom fan on your own. However, it is safer to hire an experienced electrician as working with electrical circuits can be dangerous.

If you think it is troublesome to try to obtain a permit for installing a bathroom fan, please don’t just decide not to install one. There are so many (mostly older) homes, that neglect the exhaust fan and consequently suffer many other problems. You can read my article on why bathroom ventilation is so important as motivation to get through the permit application process!

What Else Is Important When Installing A Bathroom Fan

While keeping everything legal is important, there are other factors that should be taken into account when installing a bathroom fan.

Here is everything that must be considered

Duct size

The size of the duct is crucial for the fan to work efficiently. An undersized duct will make the fan much louder and reduce its capacity to move air.

The general recommendation is to use at least the same size duct that is on the bath fan housing connector. If the duct run is longer than 20 ft consider going up one size.

Duct Type

Rigid metal or PVC duct is preferable, If the duct run is short a flex duct can be used.

Duct routing

Find the shortest and straightest path from the fan to the termination point. The fewer turns and the shorter the duct is the more efficient the entire system will be. Often the fan is vented through the roof or wall.

Duct insulation

It is vital that the duct is insulated to prevent water from dripping back into the bathroom and causing brown stains around the bathroom fan.

Also, don’t forget to place insulation above the fan housing. Find out if your fan can be covered without clearance, or it needs a box for clearance.

Fan capacity

The bathroom fan capacity is calculated according to the volume of the bathroom. I have created a bathroom fan CFM calculator you can use to find out the correct airflow.

Bathroom exhaust fan airflow CFM chart

It is important that the fan has sufficient capacity in order for it to dry the bathroom in a timely manner.

Must vent to the outdoors

The bathroom fan must ALWAYS vent outside of the building envelope. I can not stress enough how important this is.

In fact, having no bathroom fan could be better than venting it to the attic. If there is no bathroom fan the moisture damage from not having a bathroom fan will be visible in the form of growing mold in the bathroom. However, if the moist air is exhausted Into the attic or any other hidden space, the mold and mildew can grow for years without anyone noticing. This can end up costing tens of thousands to clean up.


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