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