Skip to content

How to Replace a Bathroom Extractor Fan

man replacing bathroom fan

Of all the rooms in your home, your bathroom is exposed to the most moisture, which creates high levels of condensation, especially in cold bathrooms without adequate ventilation. 

Of course, this is expected, since most bathrooms have steaming hot showers, baths – and if you’re lucky enough, a  jacuzzi bath. All of these amenities involve hot running water throughout the day, – even a hand basin with hot water can increase humidity – which creates more condensation.

Too much condensation could lead to mould and damage to bathroom accessories. That’s why it’s essential to have an extractor fan fitted. Extractor fans draw the moisture out of the bathroom, taking it outside the home.

Perhaps your current extractor fan has stopped working, or you need an upgrade – we’ve created this guide to help get your new fan fitted.

Before You Begin

If you’re putting a brand new fan in without a preexisting one already in place, you’ll have to create a hole from the bathroom to the outside, either utilizing an outside wall, or the ceiling, with proper ducting to expel damp air out of the loft.

Be sure to check beforehand for any load-bearing studs, wiring, or piping that may be in the way of your hole. If you have the building plans, this process will be very easy. However, if you don’t have the building plans, you can use an electronic device to detect anything hidden in the drywall.

Installation into a ceiling is simple, providing you have access to the loft space. 

Fan Placement

Replacing an old fan is very straightforward, since the holes, wiring, and ducting will already be in place. If you’re fitting the fan for the first time into a wall, the most efficient place to put it would be higher on the wall, opposite the door. This may not be possible depending on where the shower is located, because sometimes the shower is directly across from the door and the fan will not work if placed in the shower.

However, get the fan as close to the opposite door as possible and put it up towards the ceiling to ensure optimal air flow. Alternatively, put it above the toilet.

Alternatively, you can put the fan in the ceiling, if the bathroom is on the top floor or the only floor. You will need to duct through the loft space in this case.

If your bathroom is on the bottom floor, it would be best to put the extractor fan on the wall. If the bathroom is also not by any outside wall in addition to being on the bottom floor, it would be best to consult a contractor for how to proceed.

Materials Needed:

  • Flexible ducting
  • Saw to cut ducting to size
  • Grill covers and fittings
  • Drill and appropriately sized drill bits
  • Hammer and Chisel
  • Alternatively: Reciprocating saw
  • Screwdriver
  • Tape measure
  • PPE: Gloves, goggles, hearing protection
  • Pencils for marking where you will be cutting
  • And of course, a new bathroom extractor fan unit.


Remember, it is best to measure twice and cut once! The installation process has several steps and it is best to make sure you are installing on a clear day since you are drilling a hole to the outside of your house.

Be sure to wear proper protective equipment like gloves, goggles, and hearing protection.

Creating the Inside Hole

mark hole for drilling in wall

The first thing you will need to do is create the hole to the outside (if you don’t already have one). Ensure that you have picked a spot that is clear of studs, piping, and wiring. Then, hold the fan to the wall or ceiling and trace around the edges with your pencil. You’ll also want to mark the centre point. Drill some pilot holes for reference, angling the drill towards the centre point.

At this point you can either drill several holes as guidance for using the hammer and chisel, or use a saw to cut the drywall out.

If you go with the hammer and chisel, start by drilling guide holes about an inch to an inch and a half apart. Then use the chisel and hammer to chop out the drywall. Alternatively, you can use a handsaw or a reciprocating saw to cut the drywall out.

Creating the Outside Hole

Using your tape measure and your pencil, outline the hole to the outside. If it is not one-hundred-percent perfect, it will be okay because your ducting is flexible, but you’ll want to make it as exact as possible. When in doubt, err on the side of the hole in the outer wall being slightly lower than the hole in the inner wall.

Drill and saw your outside hole much the same way you created the inside hole. Depending on what the outer wall is made of, this will take more work. Stucco, brick, and tiles are always more difficult to cut through than basic drywall. This step takes both precision and patience.

If the outside hole is in the roof, make sure you remove any shingles or tile prior to drilling. Again, the holes do not have to line up exactly because the ducting is flexible.

Inserting the Ducting

fitting extractor fan ducting in loft

Now that you have a hole from the inside of your house to the outside, insert the ducting. It needs to be flush against the internal and external portions of the wall. Use the hand saw to trim away any excess ducting. Attach the ducting flanges as necessary.

Repair Plasterwork

At this step of the process, you’ll want to repair all plasterwork on either side of the wall or ceiling internally. Then repair any external wall plasterwork or roof cement.

Manage Electrical Connections

wiring fan electrics

Do NOT attempt any electrical work without consulting a qualified electrician, even if you’re confident in your ability to fit the new fan in.

Before doing any electrical work, be sure to turn off power at the circuit breaker. Insert all fittings for wall plugs, run cable to the fan and to the switch, and then splice in any necessary wires for your fan. The fan should be operated by a switch that you can turn on and off.

Sometimes there will be a place to attach it next to the pre-existing light switch, sometimes you will need to make a separate switch. Make sure to follow all manufacturer instructions for fan operation.

Fit the Fan Into Hole

fit bathroom fan into hole

From the bathroom, fit the fan over the wall. Trace any holes you need to drill to attach it securely to the wall. Then attach your fan.

Secure the Grill Covers

final fan grill fitting

On the fan is fully fitted and working, it is now time to attach the grill cover. For slatted designs, make sure you place it horizontally. Trace all necessary holes with your pencil before drilling, then secure the grill.

Finishing Up

Once you have done all that, all you need to do is clean up your work space and now you can enjoy your newly-installed bathroom extractor fan. You new extractor fan will need regular cleaning to ensure that it’s able to provide optimal ventilation, and to maintain years of reliable use.