Start from the top of the roof and remove the old shingles along with the flashing underlayment and vents.
Roof change plywood.
Loads will vary with the pitch of the roof.
Step 6 unroll new roofing felt over the new plywood and extend it at least 3 inches over each edge of the new plywood.
Inspect the underlying roof sheathing for damage and make any needed repairs.
Hammer down any large nails that are exposed by the removal.
Rotted plywood cannot support the weight of a roof the way healthy wood can nor can it safely grip the nails put into the roof and keep them held firm.
This is a popular option because it presents homeowners with functional but affordable roof sheathing.
Install a layer of roofing insulation as recommended by the roofing manufacturer.
If your roof carries a heavier load like if there s less pitch and or it snows in your area a roofer may recommend the use of the inch variety.
That will suffice on a roof with rafters set 16 inches apart with minimal roof loads.
A half inch cdx plywood is often used with rafter with 24 inch spacing.
Most roofs will be sheathed in plywood at least 3 8 inch thick.
Place a new plywood board in the same location ensuring the ends align over roof rafters.