Cutting the Hole
Before removing the old range hood, shut off the electricity to that circuit at the main electrical panel. Flip the light switch on the old hood to confirm that the power is off. Remove the grilles from the stove top and cover the range with a blanket. To remove the old hood, reach up into it and disconnect the electrical cable. Locate the mounting screws that hold the hood in place and remove them. Gently pull the hood from the wall (step 4). Next, mark the centerline of the upper cabinet on the back wall. Measure down 1/8 in. from the bottom of the cabinet and draw a level line across the wall. Use these two references marks to draw a 3 3/4 -in.-high x 10 1/2 -in.-long rectangle on the wall. Cut out the duct hole with a drywall saw (step 5). If you're lucky you won't hit a wall stud or other obstacle. If you do, but it's just at one edge of your hole, you can shift damper/duct connector on the rear of the unit 1 in. to the left or right. This shift is often enough leeway to miss a stud or obstacle. However, if the stud is still in the way, you'll have to remove it and install a header. Here's how: Empty out the wall cabinet that sits directly above the duct location, then unscrew and remove the cabinet. Cut a hole in the wall that's about 14 in. high x 28 in. wide. Use a reciprocating saw to cut the stud 6 in. above the location of the duct hole and 4 in. below it. Pry out the severed piece of stud. Next, make a header by nailing together two 2x4s sandwiched around a 1/2-in.-thick plywood spacer. The header must be long enough to span between the two full-length studs on each side of the hole. (For studs placed 16 in. on center, cut the header 30 1/2 in. long.) Make a double sill plate to the same length by nailing together two 2x4s. Then, reach into the wall hole and screw a 2-ft.-long 2x4 trimmer stud to each full-length wall stud. The trimmers must be level with the top of the just-cut wall stud coming up from below. If you can't fit the trimmer stud into place, enlarge the hole. Slip the double sill into the wall and screw it down into the trimmers. Insert the header and screw up into the bottom of the cut stud hanging down from above. Cut two short 2x4s to fit vertically between the sill and header. Screw one to each of the full-length wall studs inside the hole. Cover up the new framing by replacing the original drywall or cutting a new piece to fit. Conceal the wall patch with drywall tape and joint compound. Reinstall the wall cabinet and cut out the 3 3/4-in.-high x 10 1/2-in.-long duct hole. Next, transfer the duct hole location to the outside by boring a hole through the exterior wall from inside (step 6). Go outside and use the hole as a reference point to saw out a 3 1/2-in.-high x 10 1/4-in.-long duct hole (step 7).
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