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Building codes set a floor, not a ceiling. The International Residential Code establishes minimum requirements for how roofing and siding materials are attached and flashed, but it also generally requires, wherever adopted, that products be installed according to the manufacturer’s own instructions. In practice, those instructions are frequently more demanding than the code’s baseline numbers, and estimators, adjusters, and appraisers who work only from code minimums can end up understating what a compliant installation actually requires.
Asphalt shingle nailing is a familiar example. Code language may reference a standard four-nail pattern, but many manufacturers require six nails per shingle in high wind regions or at certain roof pitches, and some publish enhanced nailing patterns tied to specific wind-rated shingle lines. Starter strip application is another area where instructions often exceed a generic code description, specifying adhesive placement and fastener location that differ from a standard shingle course. Metal flashing details, including valley metal overlap and drip edge fastener spacing, also tend to be spelled out in more detail by manufacturers than by the code text itself. Fastener placement relative to the nail line printed on the shingle is another common point of manufacturer detail; a nail driven above or below that line, even if it technically penetrates the shingle, can reduce the fastener’s effective holding strength in a way that a purely code-based checklist would not necessarily flag during a visual review.
This layering of requirements has practical consequences for repair scope. If a manufacturer’s installation instructions call for a wider ice barrier extension than the code minimum for a given climate zone, or specify a fastening pattern that a code inspector would not otherwise flag, an estimate built strictly to code minimums may not reflect an installation that would actually satisfy the manufacturer’s warranty terms or the standard of care generally expected in the trade. Roofing contractors and estimators who are current on manufacturer bulletins, which are updated more frequently than code cycles, are often better positioned to catch these gaps than someone relying solely on a code reference book.
Product approval systems in some jurisdictions add a further layer beyond both code minimums and general manufacturer instructions. High wind zones outside Minnesota, for instance, may require products to carry a specific approval demonstrating performance under a defined uplift or impact test, with an installation method tied directly to that approval rather than to the manufacturer’s general instructions. While Minnesota installations are not typically governed by that kind of approval system, the broader principle applies everywhere a product carries a specific tested assembly: the tested and approved installation method, not a generic description of the product category, is what the manufacturer’s warranty and any related standard of care actually reference.
For an appraiser evaluating a disputed estimate, the relevant question is factual: what does the manufacturer’s published instruction require for this product, in this application, and does the proposed scope reflect it. That analysis stays within the technical and construction realm. Whether a given policy obligates payment for work performed to a manufacturer’s specification rather than to code minimum is a separate, policy-specific question that rests with the carrier, the policyholder, and the language they are bound by.
This article is general education about how the appraisal process commonly works. It is not legal advice, and specific procedures can vary by state and policy.
Russ Lis is a working property insurance appraiser and umpire based in Minnesota, serving clients nationwide. Contact Appraisal Resolution.