The Chicago Mafia used to weigh down victims in water by placing them in “cement shoes”. LafargeHolcim shareholders know the feeling: since Switzerland’s Holcim combined with France’s Lafarge in mid-2015 shares have submerged by nearly a third, underperforming rivals Saint Gobain and Sika. An expensive U.S. acquisition may provide a partial rescue. The fact that CEO Jan Jenisch’s biggest deal since his appointment in 2017 is outside $36 billion LafargeHolcim’s core business speaks volumes about the cement industry’s relatively dour outlook. Firestone Building Products, the U.S. division of Japan’s Bridgestone that Jenisch is paying $3.4 billion for including debt, designs flat roofs and insulation. The latter expands into “green energy” once given a fashionable environmental, social and governance twist. As a result, the acquisition will boost the proportion of LafargeHolcim’s more lucrative “solutions & products” division sales in the United States, its largest market, to nearly two-fifths and decrease that of carbon-heavy cement to around the same level. Jenisch said being “closer to the customer” is crucial for LafargeHolcim’s future success. Maybe so. But Jenisch is paying a high price – an enterprise value equal to nearly 13 times estimated 2020 EBITDA – for greater proximity. If the roofing market grows at 5% annually, as Jenisch expects, then Firestone should deliver operating profit of $262 million in two years’ time. Adding $55 million of expected cost savings and taxing the total at Bridgestone’s 27% rate means the deal would add $232 million to LafargeHolcim’s bottom line – implying a 7% return on his investment versus Morningstar’s estimated 9% cost of capital for the company. Generously throwing in another $55 million in projected sales synergies would only boost returns a bit. But fortunate timing should help Jenisch out – and underline the deal’s justification as a growth story. Incoming U.S. President Joe Biden has promised a massive infrastructure stimulus with an emphasis on sustainable building. The fact that his Democratic party now have greater sway in Congress after wins in the state of Georgia this week could help realise that pledge and turbo-charge Firestone’s expansion. Having been badly burned in the past, LafargeHolcim investors will be naturally cautious about expensive combinations. Shares which rose by 2% on Thursday suggest Jenisch has their cautious support – for now.