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