“Do Not Mix” bulletins from manufacturers typically refer to potential visual inconsistencies, not structural concerns, and are most relevant when installing a new roof system. For repairs, mixing similar shingles may be acceptable as long as appearance and performance standards are carefully evaluated in the field.
Part 1: The Facts: Shingle Lot Number & Bundle Labels
- Lot numbers = consistency. Shingle bundles are stamped with production info to ensure a uniform appearance on new installations.
- Match the codes. When replacing an entire slope, shingles from the same lot number should be used on the slope to provide the best appearance.
- “Do Not Mix” means change. Manufacturers will release bulletins when color shifts or other changes in production occur, mixing them may cause visible shading differences when installing a new roof.
- Manufacturer policies vary. For example, GAF strictly warns against mixing; however, IKO allows it in many cases except on large, uninterrupted roof sections.
- Pro-Tip
For any new roof or slope replacement, make sure the new shingle bundles all share the same lot number before you install them.
Part 2: Why It Matters in Property Claims
Differences between the lot numbers of the original shingles and the replacement shingles are typical in repair scenarios. If a close visual match isn’t possible, a full slope replacement may be required to meet appearance expectations and policy requirements.
Objective Guidance on Mix Scenarios
Mixing shingles from different production runs or manufacturers isn’t always a black-and-white decision. Objective guidance means evaluating each scenario based on field conditions—like shingle performance, color compatibility, and repair location—rather than relying on blanket assumptions. When the right course of action isn’t clear, seeking expert analysis helps ensure decisions are grounded in facts, not guesswork—protecting both the roof’s integrity and the claim.
When it comes to mixing shingles, there’s no substitute for informed judgment. Manufacturer’s guidance, lot numbers, and in-field evaluation all play a role in determining whether a repair will meet both aesthetic and performance expectations.
