n8n Workflow: Draft Roof Supplement Letters from Gmail PDFs

Automatically draft roof supplement letters from Gmail estimate PDFs—then create a Google Doc + Gmail draft for the adjuster

This n8n workflow reads roof estimate PDFs you receive in Gmail (or upload via the n8n form), extracts claim and roof details with OpenAI, checks them against your scope rules in Google Sheets, and automatically generates the missing roof supplement letter in a Google Docs document—plus a ready-to-review Gmail draft to the adjuster. It also maintains a claims log and runs a morning chase for unanswered supplements.

What this workflow does

• Triggers when an estimate PDF arrives in Gmail, when you upload a PDF via the n8n form, or on a daily schedule to review unresponded supplements.
• Filters incoming emails to continue only when a PDF is attached and the email content matches your configured estimate keywords.
• Extracts and structures data by reading the PDF text and sending it to OpenAI to capture roof facts, measurements, totals, and all priced line items.
• Validates against “Scope rules” stored in Google Sheets, comparing estimate line items to identify missing items and under-applied waste rules.
• Drafts the supplement when gaps are found: OpenAI generates supplement wording, the workflow formats the letter, saves it to Google Docs, and creates a Gmail draft addressed to the adjuster.
• Logs and summarizes by appending a record to the “Claims” sheet and emailing you a summary with missing items and links to the Google Doc and Gmail draft (or confirming the estimate looks complete).
• Morning chase: scans the “Claims” sheet for supplements without responses after your chase window, emails you a chase list, and marks rows as chased.

Use cases

• Reduce manual work: turn adjuster estimate PDFs into supplement letters without retyping roof facts and line items.
• Catch overlooked scope gaps: automatically flag missing items and waste rule under-application.
• Maintain follow-ups: run daily checks and generate a morning chase list for unresponded supplements.

Technical details

• Integrations/Credentials: Gmail, OpenAI, Google Sheets, Google Docs.
• Core logic: nodes including if, set, code, gmail, switch, and split out.
• Setup: connect credentials for Gmail, OpenAI, Google Sheets, and Google Docs, then configure estimate keywords and your “Scope rules.”