The place a slowdown in data-center construction was supposed to appear first is the place it hasn't appeared at all. Sterling Infrastructure, which does mass grading, foundations and underground utilities for data-center, semiconductor and warehouse campuses before anyone pulls a single wire, grew that business 192% year over year in the June quarter, according to its quarterly presentation. Its transportation and building-solutions segments shrank. All of the growth came from the segment closest to the AI trade.

That matters because five contractors in this corner — the companies that pour pads, energize substations and erect power plants — fell an average of 37% in the three months to 23 September, and the fall began on 28 July, when chip stocks shed more than $1 trillion in a single session and investors began reassessing near-term returns on AI spending. None of these companies had reported yet. What the subsequent earnings showed is that the group is not one story: in one name the order book and the margin are both going the wrong way, and in the other neither is.

Sterling: guidance up, multiple halved

Sterling's June-quarter revenue was $1.168bn, up 90.1%, with gross margin of 24.2% and diluted earnings of $5.00 a share against $2.31. Operating income grew 113.8% on 90.1% more revenue — leverage, not mix. Signed backlog reached $4.33bn, up 116% year over year, with combined backlog of $5.62bn and mission-critical projects at 92% of the site-development book, the company reported. Full-year guidance was raised to $4.0–4.15bn of revenue and $19.70–20.30 of adjusted earnings a share.

The shares fell on it anyway, and there is one honest reason inside the print: site-development adjusted operating margin of 24.1% against 28.3% a year earlier, because the acquired CEC electrical business runs at 11.4% against upper-20s margins in earthwork. Chief executive Joe Cutillo also pre-announced a wobble, telling investors on the August 4 call that "this, coupled with our forecast for strong revenue burn in the third quarter[,] could result in a sequential backlog decline in the third quarter," which he attributed to customer bidding-cycle timing.

Against that, the price. Sterling closed at $993.74 on 4 June and at $512.00 on 23 September, down 48.5%, having troughed at $457.60 on 2 September. On unchanged trailing earnings of $13.87 a share, the June peak was roughly 71.6x; today it is 36.5x trailing and 25.9x forward. The multiple halved while the guidance went up.

Argan: the order book that actually shrank

Argan, a 1,409-employee builder of fixed-price gas plants through its Gemma Power Systems unit, reported record July-quarter results — revenue up 61.5% to $384m, net income of $53.3m — and its shares set a new low on 22 September, three weeks later. The reason is on the other two lines. Backlog fell to $2.5bn from $2.9bn at the fiscal year's start, a $411m decline the company attributed to completions and award timing, and gross margin has stepped down three quarters running. "Consolidated gross margin has stepped down over the past 3 quarters from 25% in the fourth quarter of fiscal 2026 to 21% in Q1 of fiscal 2027 and now 19.3% in the second quarter," chief financial officer Joshua Baugher said on the September 2 call, adding that second- and third-year project ramps offer "the opportunity to enhance margin." Its fabrication arm took the acute hit: 111% revenue growth at a 7.3% margin after two projects came in with higher estimates to complete.

In fixed-price engineering and construction the margin is set at signature, so a step-down is a statement about work already sold. And Argan's book is 80% natural gas at the moment Texas froze the queue: on 3 August Governor Greg Abbott ordered an audit of every data-center project seeking ERCOT interconnection, with data centers roughly 90% of 474 GW of requests, and BloombergNEF estimates the review could delay 49.8 GW of load and cost projects up to $15bn. Management said it has seen no change in developer behavior. Matthew Smith of Chronometer Partners argued in a 22 June letter that gas-plant contractors are "acutely short natural gas" and that new construction could stop around 2028 as approved liquefied-natural-gas exports outrun supply growth.

Argan trades on 29.6x trailing earnings and 28.7x forward — the market pricing no growth for a year consensus still has at $13.04 a share. The counterweight is $1.0bn of cash and investments with no debt against a $5.25bn market value, roughly 23x excluding cash, and a trailing free-cash-flow yield above 10%.

The name that didn't break

Quanta Services, the 69,500-employee transmission and substation contractor, is the control and it sat out most of this. Revenue grew 41.1% to $9.557bn with gross margin up nearly three percentage points to 16.2%, backlog at a record $53.4bn and free cash flow of $0.9bn in the quarter; about 70% of its $33.6bn of contracted performance obligations converts within twelve months. It fell 9.6% over the three months, against 42.6% for Sterling and 49.2% for Argan. MasTec, which posted record revenue up 23% and an 18-month backlog up 30% to $21.4bn, fell 44.3% — so the selling was not company-specific either.

What connects the de-ratings is duration, not demand: the 30-year Treasury yield is around 5.3%, the highest in roughly 19 years, and a higher discount rate shrinks the present value of an order book that pays in 2028 without shrinking the book. Sterling's fall is that repricing, plus a real mix dilution from an electrical acquisition earning 11.4%. Argan's is something firmer: a shrinking order book, a margin set at signature that has fallen four percentage points, and the only genuine demand-side event in the window sitting on top of 80% of its backlog. The heading can no longer be traded as one thing.

The cheapest test arrives on a schedule nobody controls. Texas said its audit would take several months; Argan expects to add a handful of new projects over the next seven to fifteen months against capacity for a dozen jobs at once.