How To Supplement A Property Insurance Claim

By Taylor Grant, licensed public adjuster · Published November 16, 2021 · Updated September 24, 2026

The carrier's estimate is an opening scope built in twenty minutes. A supplement is how the rest of the loss gets added - and the format matters as much as the evidence.

The carrier's estimate is not a settlement offer and it is not a final measure of the loss. It is an opening scope, built by someone who was on your property for under an hour, from a template, in software with a regional price list.

A supplement is the formal, documented request to amend that scope. It is a normal part of almost every claim of any size, adjusters expect them, and the ones that get paid look very different from the ones that get ignored.

What a supplement is for

Concealed conditions. The roof comes off and the decking is rotten, the sheathing is spaced, there are two layers to tear off, the substrate will not take fasteners.

Code requirements. The jurisdiction requires ice-and-water shield, drip edge, ventilation, upgraded fasteners, sometimes full deck replacement. If your policy has ordinance or law coverage - most do - the carrier owes the code-compliant rebuild, not a like-for-like copy of a 1998 roof.

Omitted scope. Gutters, downspouts, fascia, flashing, vents, window screens, the AC condenser, detached structures, interior damage, contents.

Trades that were missed. Paint, drywall, insulation, electrical detach-and-reset, HVAC.

Overhead and profit. Where a job requires three or more trades and general contractor coordination, general contractor overhead and profit is a legitimate line item, and it is commonly omitted on the first pass.

Price corrections. The estimating database is a regional average and it lags. Real bids from real local contractors are evidence.

Matching. Where the replacement cannot be matched to what remains. Matching, in detail.

What makes one get paid

The difference is almost never how strongly you feel about it. It is these five things:

1. Line items, not narrative. Submit it in the same estimating platform the carrier uses - Xactimate on most files - with the same line-item codes, quantities and units. A supplement in the carrier's own format goes to the desk adjuster as a scope comparison. A letter explaining that you think the number is low goes in the file.

2. Evidence attached to each line. A photograph number against the line item. Moisture readings. A code section, by chapter and number, from the actual adopting jurisdiction. Manufacturer installation instructions. An invoice.

3. Sent while it is open. Photograph the decking before it is covered, the substrate before the underlayment goes on, the wall cavity before it is closed. A supplement for something nobody can see any more is an argument you will lose.

4. Reasonable. Ask for what is defensible and drop what is not. Credibility is a finite resource in a claim file and it is spent on the requests you cannot back up.

5. Dated, and followed up on a date you wrote down. "Submitted 12 October, followed up 26 October, no response" is a record. It matters if the file later needs escalation.

The mechanics

1. Notify the adjuster that a supplement is coming, ideally before the concealed condition is covered up.
2. Build the supplemental estimate with the line items, quantities and evidence.
3. Submit it in writing with the claim number, referencing the original estimate version.
4. Log the date and set your own follow-up date.
5. Follow up in writing. Escalate to a supervisor if it goes quiet.
6. If they refuse on amount only, appraisal resolves amount disputes without a lawsuit.

Do not forget the depreciation

A supplement increases the replacement cost, which increases the recoverable depreciation held back on it. Once the work is complete, the final invoice releases both the original and the supplemental depreciation. How that works.

The honest limitation

Writing a supplement that actually works needs access to the estimating software, familiarity with the line-item codes, and the local code citations. That is a real barrier, and it is most of the reason contractors and owners end up arguing about totals instead of scope.

If you have an estimate you believe is short, send it to us with your photographs. We will tell you what is missing from it before you commit to anything.

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