Methodology v1

How the material cost knowledgebase stays useful.

The durable unit is an immutable observation, not a generated ZIP page. Pages are a reversible view of validated evidence.

Observation contract

An observation records the exact catalog material, supplier channel, branch or store when applicable, source product identity, ZIP context, observed timestamp, source price and currency, package basis, normalized unit price, price class, availability, fulfillment, tax and delivery treatment, membership requirement, visibility, collection method, source URL, evidence hash, quote validity, and notes.

Freshness

Each material defines its own freshness window. Current v1 windows range from seven days for lumber, panels, copper, and NM-B cable to fourteen days for drywall and other selected products. Expiration never deletes history; it only removes an observation from the current view.

Comparable cohorts

The open-market headline cohort excludes tax-included, delivery-included, membership, contract, and quote prices. Negotiated and quote observations remain useful internally, but they are reported separately and are private unless the supplier provides written publication permission.

ZIP and ZCTA semantics

An observation's ZIP identifies the customer or serving-market context used for a store, branch, supplier quote, or sanctioned API request. The nationwide planning catalog uses Census ZIP Code Tabulation Areas (ZCTAs), which are generalized area representations rather than authoritative USPS delivery routes. Not every valid USPS ZIP has a ZCTA. Neither identifier is treated as a uniform postal-boundary price surface, and one source is never extrapolated across it.

Sparse nationwide rollout

The full ZCTA catalog is a queue, not a page factory. Collection plans select a bounded cohort, reports aggregate only active or observed locations, and builds render only active/observed private records or public records that pass every gate.

Public gate

• At least 2 fresh public observations from 2 distinct sources per material.
• At least 6 qualifying materials and 3 distinct sources per ZIP page.
• At least 1 non-big-box source per ZIP page.
• Only exact or supplier-serving local scope, source URLs, evidence hashes, approved publication terms, and an explicit dataset license.

Source access

The project uses sanctioned partner APIs and feeds, supplier-provided exports, or manually obtained quotes. It does not crawl retailer consumer sites when terms or project policy prohibit that access. Private invoices and negotiated quotes never become public data automatically.

Structured data

The reference-only release exposes a machine-readable authored-reference JSON file containing the same exact-product definitions, estimating methods, and governed citations as the guides. It contains no prices, locations, suppliers, or observations and is not an observed-price dataset. When a separately authorized public dataset exists, its landing page may use Dataset metadata and link to the aggregate JSON distribution. These pages do not use seller Product or Offer markup because Takeoff is not offering the observed supplier products for sale.