Yes, you likely need to cut the existing duct flush with the wall surface. Here's the sequence:
- Unplug the dryer and remove the old duct system.
- Cut the end of the old duct approximately flush with the wall. You can use tin snips for this.
- Hold the supplied wall assembly centered over the wall exit, mark the screw holes.
- Check for live wires in the wall with an AC voltage sensor before driving any screws.
- Install the wall anchors and mount the assembly, then connect the hose with the supplied clamps.