Loads will vary with the pitch of the roof.
Roof change plywood.
Start from the top of the roof and remove the old shingles along with the flashing underlayment and vents.
Install a layer of roofing insulation as recommended by the roofing manufacturer.
This is a popular option because it presents homeowners with functional but affordable roof sheathing.
Moisture causes wood to rot and rotten wood absorbs water even more readily than fresh wood.
Secure the plywood by inserting six penny nails along the rafters spacing them every 6 inches.
Inspect the underlying roof sheathing for damage and make any needed repairs.
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.
Rotted plywood can cause a number of issues.
A half inch cdx plywood is often used with rafter with 24 inch spacing.
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.