Shares in SIG PLC, the insulation manufacturer, got the cold shoulder from investors after warning on profits as it blamed market conditions for remaining "challenging".
Like-for-like sales in the first half of the year are down roughly 7% on last year, it said in a statement, which it acknowledged was behind expectations.
The shares fell over 12% to 23.96p.
As trading has been weaker in recent weeks, directors now have a more cautious view of when the market may improve.
Reflecting this more cautious outlook, management now expects full-year operating profit somewhere between £20 million and £30 million, down from £53 million last year.
This new guidance is well below consensus expectations of £40 million.
The Sheffield-headquartered group cited softness in its French, German and UK interiors businesses, which together represent over half total revenue based on last year.