The firm said that the "operational overruns" would wipe £1.6m from its annual profits.
Pre-tax profits for the first half of its financial year are now expected to be approximately £1.5m.
In a trading update, Severfield-Rowen said: "Further to the interim management statement on May 18, which indicated that results for the full year would see a greater weighting towards the second half of the year, we now expect that weighting to be more pronounced as a result of anticipated operational overruns of £1.6m against our estimated costs on two complex projects in the UK."
Full year profit could also be below expectations, the company warned, although it should still be better than last year.
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