A half inch cdx plywood is often used with rafter with 24 inch spacing.
Roof change plywood.
Moisture causes wood to rot and rotten wood absorbs water even more readily than fresh wood.
Rotted plywood can cause a number of issues.
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.
Secure the plywood by inserting six penny nails along the rafters spacing them every 6 inches.
Loads will vary with the pitch of the roof.
Hammer down any large nails that are exposed by the removal.
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.
Install a layer of roofing insulation as recommended by the roofing manufacturer.
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.
This is a popular option because it presents homeowners with functional but affordable roof sheathing.