You will need a partner for this step as you cannot see the ceiling from this position.
Installing exhaust fan in bathroom through roof.
If the hole is too big you ll need to patch the ceiling.
Place the fan in the cut out hole so that the bottom edge of the fan is flush with the bottom of the ceiling drywall.
Wrap the joints with duct tape.
Try to keep it close to the fan location.
Start in the attic and drill a hole through the roof in the desired vent location.
The patched areas can be repaired with spackling later.
Slide clamps over the flexible duct at both the roof cap and the fan housing then slip the clamps over the tailpieces.
From up on the roof use a jigsaw or reciprocating saw to cut a 4 in.
Attach the bathroom fan to the joist.
Cut a piece of drywall to make the ceiling hole the right size for your fan.
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This old house general contractor tom silva shows how to properly install a roof mounted bath fan vent.