Opinion,
Mr. Chief Justice Paxson:The contract in this case was in writing. The plaintiff agreed to do the excavating or digging for fifty cents per cubic yard. There was no provision that a higher price was to be charged for rock excavation, and the contract is silent as to the depth. The plaintiff testified that it was not to exceed four feet. The defendant, Phillips, contradicted this, and said he informed plaintiff that “ at particular places the foundation would have to go exceedingly deep. ... I asked him to give *173me a general price; tbe foundations might be of any depth.” The plaintiff alleges that the excavation was much deeper than four feet, and the contention is about an extra charge for the alleged increase of depth. The plaintiff and the defendants agree that no notice was given to the latter that an extra charge would be made for such reason. The defendant Phillips testified: “He (plaintiff) never said anything about extra pay or constructive measurement.” The plaintiff testified: “ I did not tell Phillips that he would have to pay extra when, we went below three and one half feet.”
The work was measured for plaintiff, not by the actual number of cubic yards, but by a rule which was designated as “constructive measurement.” This rule was given by Mr. Andress, a measurer called, as a witness by plaintiff, as follows: “ The rule of constructive measurement is made by the Bricklayers’ Association. We are not entitled to give prices outside of Bricklayers’ Association. The percentage varies from twenty-five per cent to three hundred per cent on constructive measurements. It varies from month to month; almost from day to day. As prices of labor and material advance, this scale is advanced. All contractors and builders are aware that certain allowances must be made during the progress of the work.” It is not even alleged that the defendants knew of any such rule. The defendant Phillips testified at the trial: “ I heard of constructive measurement yesterday for the first time in my life.” It is almost needless to say that the defendants cannot be bound by a rule of the Bricklayers’ Association of which they had no knowledge. This very point was decided in Corcoran v. Chess, 131 Pa. 356. We there held that a contract for mason work by the cubic yard meant a cubic yard as popularly understood, and was not to be measured by an arbitrary rule, of which the contracting party had no knowledge.
It may be the Bricklayers’ Association may adopt rules which may bind themselves, and perhaps others who deal with them with knowledge of such rules, and upon the faith of them. But before a mere usage of trade or a custom can become so firmly imbedded in the law as to govern the rights of parties, it must be so certain, uniform and notorious as probably to be known to and understood by the parties entering into *174the contract. And such usage or custom cannot be proved by single, isolated instances: Cope v. Dodd, 13 Pa. 33; McMasters v. Railroad Co., 69 Pa. 374. In the latter case it was held that, “ to establish such custom, it should be reasonable, continued, and acquiesced in by all acting within its operations.” The authorities upon this point are legion; those referred to are sufficient. When a custom is so established, parties may be presumed to have acted with reference to it, and the law will in some instances write it into their contract. But since the world began the law never wrote into any man’s contract such a usage or custom as this. It has no element of certainty. In the language of plaintiff’s own witness, “it varies from month to month; almost from day to day.”
The defendants by their second point asked the court to instruct the jury that “ a custom of trade, to be binding, must be so universal that parties dealing with the subject must be presumed to know it, and so certain and invariable that there can be no room to doubt its application to a given case.” This point was refused. For the reasons above given, we think this was error. As the defendants had no knowledge of such custom, actual or constructive, they áre not affected by it.
We can understand how the depth of an excavation would enter largely into its cost. The written contract was for a certain price, without regard to depth. If the plaintiff entered into it without any misrepresentation on the part of the defendants with regard to the depth, he cannot recover extra compensation. It is not enough that he entered into it carelessly, and without an examination of the plans; and, as the contract specified no depth, if the defendants desired him to go deeper than his understanding of the agreement called for, it was his plain duty to notify the defendants that he would increase the price.
We think it was error to exclude the testimony of John H. Dye. He was asked: “ What knowledge, if any, have you of the rule of constructive measurement ? ” He had previously testified: “ I am engineer and surveyor, and was for more than thirty years the city surveyor. I am frequently called upon to make measurements for parties, of work done, both for the city and for private parties.” If the usage referred to was so general as to be binding upon the defendants, Mr. Dye must cer*175tainly have heard of it from the very nature of his business; and if he had not such knowledge, how could it be imputed to the defendants?
We have not noticed the assignments in detail. What has been said sufficiently covers the important questions in the case.
Judgment reversed, and a venire facias de novo awarded.