How to Install Vent Ducting for a Microwave Over the Stove

Open up the cabinet above where the microwave will be installed. Clear out any objects inside.

Place the microwave ducting and screw openings template on the floor of the cabinet. Use this to trace the area where the top of the microwave duct will enter the cabinet. Drill out screw holes on the template to help secure the microwave from below. If your microwave oven did not come with a template, use measuring tape to measure the distance between the vent opening in the top of the microwave and the sides of the appliance. Transfer these measurements to the bottom of the cabinet.

Cut a hole in the bottom of the cabinet with a jigsaw. Use a drill to start the hole and make an opening big enough for the jigsaw blade. Trace around the vent-opening mark until the piece of the cabinet falls out. Sand down any rough edges with a file or sandpaper.

Knock a hole in the outside wall inside the cabinet for the microwave vent cap. How this is done will depend on the materials of your wall. For brick walls, it will be easier to work from the outside. Measure the distance from the floor in the kitchen to the bottom of vent cap ducting inside the cabinet. Transfer this measurement outside. Mark the bottom of the vent cap ducting height on the outside wall. Hold the vent duct to this mark and trace around to give yourself a guideline. Use a drill with a mortar bit to drill around the outside of the hole. Knock out the brick pieces with a hammer or chisel. Remove any interior wall paneling with a jigsaw or keyhole saw. The process is the same for nonbrick exteriors, except you don't have to use a mortar bit or hammer to knock out pieces of the wall. File down any rough edges on the wall.

Install the vent cap from the outside. It should fit snugly into the opening in the wall.

Have an assistant hold the microwave in place beneath the stove. The vent opening in the top of the oven should fit through the hole you made in the bottom of the cabinet. Secure the microwave to the bottom of the cabinet using the screws provided.

Dry fit your ducting together. Trim any pieces, if needed, with tin snips. Shorter runs may only need a single elbow between the microwave and the wall duct, while longer runs may need some straight ducts or more elbows. Secure the duct pieces with duct tape.

Fill in any cracks between the vent cap and the wall opening with weatherproof silicone caulk.