The plaintiff and defendant own adjoining - lands in Haverhill. Neither was able to show by any recorded plan or deed the exact location of the boundary line between them. The defendant has constructed a *315heavy masonry wall upon what it contended was its own land near the true boundary. A master, whose report has been confirmed by the Superior Court, has found that this wall in large part encroaches upon the land of the plaintiff. The judge has ordered the entry of a decree directing the defendant to remove the encroachment and has reported the case for our determination. The judge ruled that he had no discretion other than to order a mandatory injunction to issue.
The defendant contends that, in the circumstances reported by the master, the ruling and order are wrong. It does not deny that the law is as stated in Szathmary v. Boston & Albany Railroad, 214 Mass. 42, 44, “when one without right attempts to appropriate the property of another by conduct which will ripen into an easement, a court of equity will compel the trespasser to undo as far as possible what he has wrongfully done.” It attempts to distinguish Curtis Manuf. Co. v. Spencer Wire Co. 203 Mass. 448, Kershishian v. Johnson, 210 Mass. 135, Brooks v. Rosenbaum, 217 Mass. 172, Congregation Beth Israel v. Heller, 231 Mass. 527, Boston & Albany Railroad v. Terminal Realty Corp. 252 Mass. 165, and Marcus v. Brody, 254 Mass. 152, which have enforced the law there stated, on the ground that, in all those cases, there was deliberate invasion of rights of another which could not be regarded as innocent; while here, as it contends, there was honest ignorance of the true location of the boundary and honest belief in the validity of the title it asserted with a reasonable basis for its belief.
The master has found that the defendant “entered upon the land of the plaintiff and built its wall as aforesaid in good faith and under the belief that it was not trespassing upon the land of the plaintiff,” but that notice was given by the plaintiff, within a few days after excavations for the wall were begun, that she owned the land on which it was proposed to build the wall and protested against its use. The bill was filed on September 6, 1927; and there is nothing to show any unreasonable delay in asserting the *316plaintiff’s rights. The report discloses that doubt might well exist whether the title asserted by the plaintiff arose from anything other than long continued adverse possession in her predecessors; but evidence of such adverse possession was abundant and within the defendant’s control. The master found that no financial loss to the plaintiff had been caused.
We think that one who knows of claims to land which he proposes to use as his own, proceeds at his peril if he goes forward in the face of protests from the claimant and places structures upon the land. It is familiar law that buildings placed upon real estate by a trespasser become the property of the true owner of the real estate. A claim of ownership must be made good if it is to bar a trespass. Undoubtedly there may be circumstances which a court of equity will regard as full justification for refusing to require removal of a nuisance created under claim of right and endured when it might have been stopped; especially when great and disproportionate loss results to its creator, and the value of the land is not affected. Mere belief in one’s right, however, no matter how honestly and reasonably entertained, is not such a circumstance; nor is great expense of removal, when there has been a deliberate invasion of a plaintiff’s title to real estate, and protest, followed by resort to the courts to ascertain the legal rights of the parties.
The ruling was right and the order proper.
Order for final decree affirmed.