The engineer should be liable for any delays and costs incurred as a result of his errors. Late completion claims are the most difficult to fight since late completion can be due to numerous factors.
He may not be responsible under contract to the contractor since he did not have a direct contract with the construction contactor, he could be liable under tort.
Most jurisdictions do not allow penalty clause in contracts. (You may have to have a bonus clause in the contract for early completion to get a penalty clause to stand.) They only allow damages for late completion. These damages can be actual damages or liquidated damages, which are simply an estimate of the damages. If the estimate is not a reasonable estimate, based on the knowledge of damages at the time, the courts may throw out the liquidated damages clause as a penalty clause. Therefore the contractor should not have been penalized for late completion.
The engineer may be liable for actual damages suffered by the contractor as a result of his errors. The standard of performance is not the highest standard of engineering services but what was a reasonable performance of professional skill.
If the engineer’s errors did in fact cause the late completion the owner could also sue the engineer for the costs of the delays.
Proper contract language is the best defence.
Of course I am not a lawyer so what do I know about law. The contractor could be simply following the tactic “sue them all and let the judge sort it out”.
Rick Kitson MBA P.Eng
Construction Project Management
From conception to completion