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.
Roof change plywood.
Rotted plywood can cause a number of issues.
Loads will vary with the pitch of the roof.
That will suffice on a roof with rafters set 16 inches apart with minimal roof loads.
Most roofs will be sheathed in plywood at least 3 8 inch thick.
Hammer down any large nails that are exposed by the removal.
Secure the plywood by inserting six penny nails along the rafters spacing them every 6 inches.
Install a layer of roofing insulation as recommended by the roofing manufacturer.
Inspect the underlying roof sheathing for damage and make any needed repairs.
Start from the top of the roof and remove the old shingles along with the flashing underlayment and vents.
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.
A half inch cdx plywood is often used with rafter with 24 inch spacing.
Place a new plywood board in the same location ensuring the ends align over roof rafters.