Mr. Justice Barnes

delivered the opinion of the court.

7. Building and construction contracts, § 100*—what is income petent evidence as to deduction front price. In an action on a building contract, proof of an agreement between the plaintiff, a contractor, and an architect for deduction of the cost of unfinished work from the contract price was not competent on the amount to be deducted, as the actual cost of finishing the work was the best evidence of what should be deducted, unless it was a matter of express agreement and relied on as such. 8. Building and construction contracts, § 83*—when suit is premature. In a suit by a contractor for a balance due on a building contract, where the contract provided that the balance was not due until thirty days after completion of the work, and only on certificates signed by the architect, a suit commenced before the expiration of such time was premature, and the plaintiff could not contend that the refusal of the architect to issue certificates before the expiration of such time was fraudulent. 9. Building and construction contracts, § 83*—what is condition precedent to suit. Where a contractor’s right to recover a balance due on a building contract depended upon obtaining an architect’s certificate showing the amount due, the obtaining.of such certificate was a condition precedent to any right of action which condition was to be strictly complied with, or good and sufficient excuse shown for noncompliance. 10. Building and construction contracts, § 83*—when arbitration is condition precedent to suit. Where a building contract provided for arbitration in case of dissent from a decision of an architect, the refusal to issue a final certificate for the balance due under the contract was a decision by the architect, and in such ease arbitration was a condition precedent to a right of action for the balance. 11. Building and construction contracts, § 80*—when suit is premature. Where a building contract provided for payment of ninety per cent of the contract price on completion of the contract, and.the balance thirty -days afterwards, but the contractor demanded the entire balance on completion of the work, his demand was premature.