Roofing Best Practices (Standard Techniques)

Trying to decipher standard roofing techniques or best practices. When performing a re-roofing job on a 100+ year old home with a 10-12 pitch roof, would it be standard to just shingle over the ‘rough-cut’ lumber that is the ‘underlayment’ or to apply new underlayment (plywood, OSB, etc.)? In addition to this, would the shingles be placed directly on the roof or would there be any felt placed prior to the shingles? The geographical area is northern NY, norther of Lake Placid, NY where there is over 70" of snow annually.
Please help me correct a roofer’s mistake that created more leaks after they performed the replacement :twisted:

Is this still in the bidding process or has the roof already been done?

New plywood should have been put on and underlayment.

Felt is probably code, but the decking is a site inspection and the answer is, It Depends.

If it was skip sheathing, with approximate 2" gaps between each 1" x ?" plank board, then for sure it needed a deck sheathing to be installed.


Okay, to answer all of the questions:
Yes, the roof is already done and I have been in constant discussions with the original roofer to correct the problems.
I agree that there should have been the underlayment and even had lengthy discussions and mentioned it in an addendum to the contract.
As with homes built around the turn of the 20th century (evidence between 1898-1904 for my home) and the rural area I am located, the roof materials were ruff-cut and not uniform in length or shape. So there are areas that it is butted next to each other and other areas on the same board that has a gap of over an inch. Most boards are eight to ten inches in width, with between one to two inches in thickness.
This site has been a godsend and am very thankful for the professionals that contribute and assist the novices of the world, passing on your gift!