01
Search several kinds of evidence
Look for dated exterior photographs, maintenance invoices, construction drawings, material receipts, and correspondence about roof work. Local archives or an institution's own records may contain useful views. Label the source and date of each item. A photograph of an earlier roof is evidence of that moment, not automatic proof of the building's first roofing arrangement.
02
Compare records with the building
Ask the project team to relate documentary evidence to surviving material and details. Conflicting records should be noted rather than quietly resolved by guesswork. Use the findings to explain which features are known, which were altered, and which remain uncertain. Preserve the archive summary with the new repair record so the next project starts from accumulated knowledge.