Australia’s largest building-materials manufacturer, Boral, saw its underlying net profit drop 7% to $440.1m for the 12 months ending in June—below the average analyst forecast of $476m. And the company warned that an even bigger decline in profit could be ahead, Reuters reported.

Boral plans to pick up the slack with its infrastructure and industrial building work. However, the company conceded that the decline in home builds and the start of large-scale infrastructure projects would push its profit down another 5% to 15% in 2020.

The company’s shares also slumped, falling more than 20% by the afternoon of 26 August—its biggest one-day fall since listing in 2000.

Home prices in the country began to flatten in June, with the help of interest-rate cuts and relaxed lending rules luring buyers back to the market. However, the home-building sector still lags as developers wait for longer-term forecasts before greenlighting projects, according to Danial Moradi, equities strategist at Lonsec Research.

“It remains to be seen how these lower interest rates filter through to the housing market and whether the availability of credit to the banks is going to play a part in terms of a rebound,” Moradi said.

Boral is taking full ownership of its higher-margin plasterboard unit USG Boral Australia and New Zealand, from a half share. This is a part of a two-step reset of a joint venture with Germany’s Gebr Knauf KG.

The deal expanding to another joint venture with the German company to include sales in China and South-East Asia will cost Boral US$441m in total.