James Hardie shares hit a record high after the company doubled its first-half profit amid long-awaited signs of improvements in the US housing market.
Investors added $690 million to the building materials company, pushing its shares up 14.9 per cent.
The surge put its value at $5.3 billion, more than its rivals CSR and Boral combined.
James Hardie, which is domiciled in Ireland and reports in US dollars, recorded an operating profit of $US108.3 million ($116 million) for the six months to September 30, up from $US56.3 million a year earlier.
This excluded asbestos, regulatory and liability adjustments, which would put its profit higher at $US194.1 million. It upgraded its full-year earnings target to $US180 million to $US195 million.
James Hardie, dogged for years over its past involvement in asbestos production, revealed a rise in the number of claims relating to mesothelioma, the cancer caused by prolonged exposure to asbestos.
Chief executive Louis Gries said the second quarter had benefited from an increase in sales in its US and European businesses due to improvements in the housing and construction sectors.
James Hardie dominated the US market for fibre cement. It also made flooring and interior walls for residential construction.
"Last year, we invested significantly in organisational capability in expectation of market growth in the US," Mr Gries said. "This year we are benefiting from that investment, as evidenced by improved earnings before interest and tax margins."
James Hardie expected further improvements in the US and Australian housing markets and announced plans for a $100 million expansion in the US.
The company declared a dividend of US8¢ per share, up from US5¢ a year earlier. This helped shares in the company jump $1.56 to close at $12.00.
Credit Suisse analyst Andrew Peros said investors were buoyed by its strong cash position and its investment plans in the US.
"This highlights management's confidence in the US housing outlook and underpins the longer-term growth strategy."
James Hardie said its results had also benefited from the fall in the Australian dollar, which reduced its liability for asbestos claims by $US90 million.
Its payments for asbestos claims are tied to its cash flow. It pays up to 35 per cent of its annual net operating cash flow to the asbestos fund.