
    W. A. L. Schaefer, Appellant, v. Benjamin G. Elser et al., Appellees.
    Gen. No. 22,446.
    (Not to be reported in full.)
    Appeal from the Superior Court of Cook county; the Hon. Denis E. Sullivan, Judge, presiding. Heard in this court at the October term, 1916.
    Reversed and remanded with directions.
    Opinion filed December 18, 1916.
    Statement of the Case.
    Bill by W. A. L. Schaefer, a corporation, complainant, against Benjamin Gr. Elser et al., defendants, to foreclose a mechanic’s lien against certain real estate of defendant Elser. From a decree modifying the master’s report in which the complainant was allowed the full amount of its claim, complainant appeals, and defendant Elser assigns cross error.
    
      Albert Goetz, for appellant.
    Francis J. Sullivan and Thurecan, Hume & Kennedy, for appellee Benjamin G. Elser.
    Abstract of the Decision.
    1. Building and construction contracts, § 65
      
      —When decision of engineer may be impeached. The decision of an engineer pursuant to a contract providing that any controversy or dispute arising under it should be settled by the engineer, whose decision was to be binding upon the parties, may be impeached for fraud or mistake.
    2. Building and construction contracts, § 65*—what are not final certificates. Certificates issued by an engineer before all the requirements of a building contract are met are not final certificates so as to be conclusive upon the parties under a contract providing that in case of controversy or dispute the engineer’s decision in case of final certificates shall be binding upon the parties.
    3. Building and construction contracts, § 52*—what amount owner may deduct from contract price where building contract not substantially performed. Where a building contract is not executed in substantial compliance with its terms, the owner has the right to deduct from the contract price what it would cost him to make the building conform to the plans and specifications agreed upon.
    4. Damages, § 14*—what is basis for rules of assessment. The rules for the assessment of damages are based, in general, upon the principle of compensation.
    
      
      See Illinois Notes Digest, Vola. XI to XV, and Cumulative Quarterly, same topic and section number.
    
   Mr. Justice Dever

delivered the opinion of the court.  