How to Build a Shower Vent

Mark the placement for a shower vent between the toilet and the shower. Drill a reference hole into the attic space so you can plan the size for the opening you will need. Bore a hole into the attic with a 3/8-inch spade bit.

Go into the attic space to clear away insulation from the drilled hole area. Use the reference hole to determine the installment footprint for the fan. Measure the vent fan housing and locate space for it between two joists near the reference hole. Work around obstacles, such as pipes or wiring, in the attic.

Use chalk to mark the placement of the opening between the joists in the attic. Go back into the bathroom to mark the cutout in the ceiling. Use a framing square to draw the outline of the rectangle for the fan venting unit.

Put on goggles and a paper mask or a respirator. Use a jigsaw or drywall saw to cut out the ceiling material you’ve marked. Support the weight of the ceiling cutout with one hand as you cut. Lift it out and set it aside for the trash.

Assemble the fan for installation from the attic side. Attach a 4-inch elbow duct at a 90-degree angle to the outlet port of the fan. This port is located on the side of the fan housing. Position the elbow duct to face straight up. Secure it to the port with foil duct tape.

Remove the knockout hole located on the side of the fan housing. Attach a cable connector. Slide four metal brackets into the tabs that stick out from the fan’s sides. Set the vent unit over the ceiling cutout hole. Place it between the joists and carefully line it up with the opening.

Extend brackets on the unit until they reach the sides of the joists. Use 1 1/2-inch screws to attach each separate bracket to a joist. Slip one end of flexible duct included with the unit over the elbow you attached to the fan unit. Use duct tape to secure the flexible duct in place.

Run the new or existing electrical cable through the connector. Tighten the connector screw to hold the cable in place.

Find a desirable place on the attic sidewall to create an exit point for the flexible duct. Select a spot within 6 feet of the vent fan and between two studs in the wall. Find points of reference on the house exterior to figure out where to cut an exit hole. Measure from the house corner or from the outside soffit, for example. Draw the hole on the house siding and cut it with a 4-inch hole saw.

Use foil duct tape to attach the connector duct to the wall cap. Slide the wall cap into the duct hole from outside. Push it against the house siding tightly. Cut a gasket to fit the wall cap out of foam rubber. Pull out the wall cap and apply a bead of silicone adhesive to the siding and the gasket around the opening.

Push the wall cap into the hole and press it against the siding. Attach the wall cap with four screws to the siding. Go into the attic and connect the flexible duct to the exhaust hole. Be careful as you maneuver the duct so it will not tear. Use foil duct tape to attach the duct end to the wall cap’s connector duct.

Hook up the electrical wiring for the vent's fan motor and attach the grille cover from the bathroom side.