Field Assembly · Construction materials
Materials Monitor
Free public resource · dated monthly editionsField Assembly · Construction materials

Construction-material prices, in context and on the record.

Follow changes in lumber, metals, gypsum, and concrete through a small set of public price and supply measures. Each dated edition explains what moved, what the evidence can show, and where the comparison stops, with downloadable data and sources you can check. No account, payment, or email address is needed to read or download anything here.

The comparison

Edition 1: September 2026 · Published edition
Material and measureLatestMonth over monthYear over yearSource and status
Softwood lumberPPI, softwood lumber · WPU0811294.9Aug 2026−1.9%+11.8%BLS PPI, preliminary
CopperPPI, copper wire and cable · WPU10260314602.5Aug 2026+4.2%+27.2%BLS PPI, preliminary
SteelPPI, steel mill products · WPU1017381.2Aug 2026+1.7%+23.4%BLS PPI, preliminary
AluminumPPI, aluminum mill shapes · WPU102501370.9Aug 2026−4.4%+27.3%BLS PPI, preliminary
Gypsum productsPPI, gypsum products · WPU137484.8Aug 2026+0.7%+0.2%BLS PPI, preliminary
Ready-mix concretePPI, ready-mix concrete · WPU1333395.2Aug 2026+0.1%+2.3%BLS PPI, preliminary

Producer price indexes, not delivered prices. Each index has its own base period, so levels are not comparable across rows; the changes are. Month over month is against the prior month; year over year is against the same month a year earlier. Every figure is in the edition's downloadable tables with its source file and retrieval time.

01The materials

Six material groups, one edition a month

"Building materials got more expensive" can hide very different movements. Lumber may move differently from gypsum; raw copper may move differently from wire and cable; cement is an input to concrete, not another name for it. Each edition follows one producer price index per group and a few context measures chosen to answer a stated question, and keeps the groups apart. There is no composite index here, because averaging six selected indicators would not describe any project's budget.

MaterialWhat the measure coversCore public sourcesMeasure
01Softwood lumberSoftwood lumber as it leaves the mill: dimension lumber, boards, timbers. Not plywood, OSB, engineered wood or treated lumber.BLS PPI WPU0811 · Census housing startsWPU0811PPI, softwood lumber
02CopperCopper wire and cable as a manufactured product, read against the LME copper price. Not plumbing tube, fittings or scrap.BLS PPI WPU10260314 · World Bank LME copperWPU10260314PPI, copper wire and cable
03SteelSteel mill products: sheet, plate, bar, structural shapes, pipe and tube as they leave the mill. Not fabricated steel, rebar installed or hardware.BLS PPI WPU1017WPU1017PPI, steel mill products
04AluminumAluminum mill shapes: sheet, plate, extrusions, foil. Not windows, siding, gutters or other finished products.BLS PPI WPU102501 · World Bank LME aluminumWPU102501PPI, aluminum mill shapes
05Gypsum productsGypsum products, with the narrower gypsum building materials index beside it. Not the price of any one wallboard product, and not installation.BLS PPI WPU137 · WPU13710102 (building materials) · Census housing startsWPU137PPI, gypsum products
06Ready-mix concreteReady-mix concrete delivered by producers, with the cement index beside it. Not precast, block, aggregates or placement.BLS PPI WPU1333 · WPU1322 (cement) · USGS cement shipmentsWPU1333PPI, ready-mix concrete

The measures are producer price indexes: what producers receive for products as they leave the plant, in index form. They are not delivered prices, not quotes, and not any supplier's cost. The materials page says for each one what it covers, why it matters and what it does not represent.

02An edition

What an edition contains, and what comes with it

Every edition has the same parts in the same order: the read, the comparison table, historical charts, material notes, context, uncertainty, and the record. Observations, calculations and interpretation are kept apart. A representative question it is written to help with: between the original estimate and the rebid, which material categories rose, which fell, and how does that compare with the explanation we were given?

Beside the text, each edition page carries a suggested citation with a copy button; CSV tables of the source-reported data, the charted series and the calculated measures, at full precision, with a data dictionary; the retained source files with their retrieval times and hashes; and the timestamp record, where one exists, that shows when those files existed. Corrections are dated on the page and the original text stays visible.

An edition states market evidence. It cannot establish a contractor's actual costs, validate an invoice, determine a fair markup, or decide whether a contractual adjustment is permitted. It does not forecast. The record can support a reasonable explanation as readily as it can show an unsupported one.

03Method

Public sources, retained evidence, dated claims

This publication follows Field Assembly's standing practice: first-party sources, quoted exactly and dated; every capture retained; evidence kept apart from judgment; corrections made on the record.

Sources

BLS producer price indexes, the World Bank's monthly commodity prices, USGS cement surveys and Census housing starts, fetched by script from official downloads. No paid subscriptions, no scraped retail listings. Producer indexes, exchange benchmarks and delivered prices are never treated as the same thing.

Evidence

Each edition ships with the source files as received, their retrieval times and hashes, the calculations, and the edition as delivered. Files are hashed into an append-only chain anchored by RFC 3161 timestamp tokens where an anchor run has been made; the edition page says whether one has.

Limits

A timestamp shows a captured record existed by a date, not that a source's figure was correct. Copying public statistics creates nothing exclusive; the work is selection, consistent comparison, transparent calculation and preserved context, with the distinctions the sources themselves draw kept intact.

04Updates

Everything is on the site. Email is optional.

New editions appear at /latest/ and in the editions list. To be told by email when an edition publishes, write with "Materials Monitor" in the subject line; the message is a notification and nothing more. Nothing on this site is withheld from readers who do not write.

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