01
Use two clearly labeled lists
Put measured work and confirmed selections in one list. Put concealed deck conditions, unresolved access, and incomplete details in another. Ask which uncertain items can be clarified by investigation and which can only be assessed during opening. An allowance should state the assumption it represents, not simply conceal an unknown inside the total.
02
Update the budget when evidence arrives
For example, a limited investigation may establish the condition of one roof zone while leaving another inaccessible. Revise only the assumptions the investigation actually resolves. Keep the date and reason for each revision so the owner can distinguish added scope from improved information. This is a planning method, not a promise that a roof project will have no surprises.