Design professionals are held to a professional standard rather than to a warranty of results, which shapes every claim against them.
Standard of care. The degree of skill and care ordinarily exercised by similarly situated professionals in the community. A design that could have been better is not negligent; one falling below the standard is. Expert testimony is required to establish it in nearly all cases.
No implied warranty that the design will achieve a particular result, and contractual language creating one is usually resisted and is frequently uninsurable.
Economic loss rule. Bars negligence claims for purely economic loss between parties in contractual privity in many states, and its application to contractors suing designers without privity varies considerably by jurisdiction.
Certificates of merit. Many states require an affidavit from a qualified professional at filing, attesting that the claim has merit. Failure to file one results in dismissal, sometimes with prejudice.
Statutes of repose apply and are frequently shorter than general limitation periods.
Limitation of liability clauses in design agreements, capping exposure at the fee or a stated amount, are enforced between sophisticated parties in most states and void in a few.
Insurance. Professional liability policies are claims-made with defence costs typically inside the limit.