When replacing your roof, be prepared to run into some unexpected repairs. Even a roof that looks like it's never had a leak could have some damage that needs to be repaired before installing the new shingles.
Decking is the wood between the primary structure of the home and the roof underlayment. In the Lansing area, this is usually made up of 3/4 plank boards, plywood, or OSB (Oriented strand board). This provides a flat surface for the shingles to fasten to. If moisture penetrates to this portion of the roof, it will most likely need to be replaced. This replacement will happen once the shingles are off the roof and before the new underlayment is installed.
Truss & Rafter Repair
A truss or rafter is the the internal framing portion of the roof that holds up the structure. It is usually made up of wood lumber and runs from eave to ridge. If moisture penetrates through the decking and reaches the framing, that could potentially mean more repairs. This could mean either cutting out the rotted area (Rafter replacement) or installing another piece of lumber along side it to reinforce the area (Sister rafter).
Soffit & Facia Repair
Soffit is the area underneath the overhang on the eave edge, while facia is the face of eave edge where the gutter attaches. They can be made up of wood, aluminum, or a combination of both. If moisture builds up on the eave edge and penetrates these areas, they may also need to be replaced at the time of installing a new roof. This also may require replacing any aluminum that may not be reusable.
Read Here: How To Choose a New Roof