In an action to recover the unpaid balance on a plastering contract and for extra work, judgment modified by striking out the separate amounts awarded to plaintiffs and substituting therefor an award to plaintiffs of $10,380.73 plus $216.43 costs, a total of $10,597.15, and as thus modified judgment, in so far as an appeal is taken therefrom, unanimously affirmed, with costs to appellant. We find the balance due on the contract, less proper credits, to be $10,380.73. Under the contract, plaintiffs were not authorized to furnish extra material and labor without a written order and certificate, and none were obtained. However, we have examined the evidence and we do not find that plaintiffs have established the performance of the work for which extra compensation is claimed. Interest should not be allowed on sums which the appellant had a right to retain under the contract. Present — Lazansky, P. J., Carswell, Johnston, Adel and Close, JJ.