Deemer, J.
1 *2112 3 *2124 5 6 *2147 *210In support of the ruling of the lower court appellee insists: (1) That -under the facts recited plaintiffs are not entitled to a mechanic’s lien; (2) that the action is barred by the statute of limitations; (3) that the action cannot be maintained, because based upon oral contract, the statute providing that such agreements must be in writing; (4) that the party-wall statute, giving one person the right to build upon the land of his neighbor, is unconstitutional and void; (5) that, such statute being void, no recovery can be had for a wall erected thereunder; and (6) that where a building wrongfully laps over upon another’s land, said person has the right to use it without making compensation. In the statement preceding this opinion, it will be noticed that plaintiffs built the wall upon the dividing line between the two lots with the knowledge and consent of the defendant, and with the promise on his part to pay one-half the cost thereof as soon as he should use it. Without reference to the party-wall statute, plaintiffs were licensees, and, having rested half their wall on the defendant’s land under an express promise by defendant to pay therefor when he should use it, there is no reason why they cannot, as at common law, recover upon the promise. Rindge v. Baker, 57 N. Y. 209; Bodell v. Nehls, 85 Iowa, 164 (52 N. W. Rep. 123); Zugenbuhler v. Gilliam, 3 Iowa, 391; Day v. Caton, 119 *211Mass. 518. It is said, however, that action is predicated upon the party-wall statutes, and that such an agreement cannot be proven by parol. These statutes, so far as material, are as follows: Code, section 2019: “In cities, towns and other places surveyed into building lots, the plats whereof are recorded, he who is about to build contiguous to the land of his neighbor may, if there be no wall on the line between them, build a brick or stone wall at least as high as the first story, if the whole thickness of such wall above the cellar walk does not exceed eighteen inches, exclusive of the plastering, and rest one-half of the same on his neighbor’s land; but the latter shall not be compelled to contribute to the expense of said wall.” Section 2020: “If his neighbor be willing and does contribute one-half of the expense of building such wall, then it is a wall in common between them, and if he refuses to contribute to the building of such wall, he shall yet retain the right of making it a wall in common by paying to the person who built it one-half of the appraised value of said wall at the time of using it.” Section 2027: “Every proprietor joining a wall, has, in like manner, the right of making it a wall in common, in whole or in part, by repaying to the owner of the wall one-half of its value or the one-half of the part which he wishes to hold in common, and one-half of the value of the ground on which it is built, if the person who has built the wall has laid the foundation entirely upon his own ground.” Section 2030: “This chapter shall not prevent adjoining proprietors from entering into special agreements about walls on the lines between them; but no evidence of such agreements shall be competent unless it be in writing, signed by the parties thereto, or their lawfully authorized agents. * * *” -Now, we have held that when *212the contract is the same in fact as that which the law makes for the parties, it is not within the meaning of this section. Wickersham v. Orr, 9 Iowa, 253. The contract relied upon in this case is not different from that which the law made, and it is not void because it was in parol. It is said, however, that sections 2019, 2020, and 2027 are unconstitutional, because they authorize the taking of private property for private use, and without compensation. Concede, for the purpose of the case, that this is so; yet how does this affect the validity of the contract made between the parties? If these sections are held unconstitutional and void, in so far as they authorize thebuildiug of awall upon the property of another, they certainly should be considered in construing another section which appellee relies upon and concedes to be valid. While no right may be based upon an unconstitutional act, part of its provisions may be considered in construing other provisions, confessedly good, in arriving at the correct interpretation of the latter. Appellee contends, however, that the agreement, if good, cannot be enforced, because this is a suit in equity, and that remedy upon the contract must be by action at law. The ready answer to this contention is the statute (Code, section 2514), which provides, in effect, that an error as to the kind of proceedings adopted shall not cause the abatement or dismissal' of the action, but merely a change into the proper proceedings; and a transfer to the proper docket. See Mills v. Hamilton, 49 Iowa, 105; Conyngham v. Smith, 16 Iowa, 471; Lewis v. Soule, 52 Iowa, 11 (2 N. W. Rep. 400); and many other cases noted in McClain’s Code & Supp., at section 3719. It is argued, however, that this action is founded upon the party-wall statute, and that this statute is unconstitutional, for the reasons before stated. That it comes very close to the line must be conceded. But *213the fact that it has existed for more than forty years, and has been generally accepted and recognized as valid and enforceable, is strong reason for sustaining the act, even if we were disposed to doubt, as a new question, its constitutionality. Cooley, Const. Lim., p. 86; Wurts v. Hoagland, 5 Sup. Ct. Rep. 1086; State v. Blake, 36 N. J. Law, 443; Bingham v. Miller, 17 Ohio, 446. We think that the act in question is not so plainly in derogation of the constitution (article 1, sections 9,18) as that we ought to hold it invalid. Indeed, in case of doubt, it is our duty ' to uphold the act. Titles to real estate are held subject to such legal conditions as may, from time to time, be established. They are subject to such statutory and police regulations as affect the safety and good order of society. A tract of land, from its mere location with respect to another, may owe it a servitude; and one must so use his own as not to unnecessarily injure another. As said in the case of Evans v. Jayne, 23 Pa. St. 34: “The law relating to party-walls is no invasion of the absolute right of property. It prescribes simply a rule for the convenient, economical, and safe enjoyment of property by the owner.” And we may add that such law prevents disputes and unseemly contentions between “neighbors,” and, as an exercise of the police power, is valid. See, also, Hunt v. Ambruster, 17 N. J. Eq. 208. What are known as “betterment statutes,” or, as they are denominated in the laws of this state, “occupying claimants’ acts,” have been sustained on substantially the same theory. See Tiedeman, Lim., pages 366, 367, et seq.; Cooley, Const. Lim. (6th Ed.), pages 476-478, et seq.; Childs v. Shower, 18 Iowa, 261. Each of these enactments was borrowed from the civil law, and has for its basis the equitable doctrine that “equality is equity.” Neither takes from the proprietor of the land anything except for benefits received. Nor can they be said to be violative *214of the constitutional provisions with reference to private property, for the reason that they adjust the equities of the parties as nearly as possible according to natural justice. Under the party-wall statute, the adjoining proprietor is not bound to contribute to the ■expense of the wall.' No burden is cast upon him until he makes such use of it as" to indicate that he desires to use the wall in common. At most, he parts with the usé of not to exceed nine inches in width off the side of his land as an easement in favor of his neighbor. Compulsory easements for the public good are quite common to our law. See the law with reference to drains, dams, and division fences. McClain’s Code, sections 1826, 1845, 2822, et seq. There are some authorities which hold to a contrary doctrine. See Wilkins v. Jewett (Mass.) 29 N. E. Rep. 214; Allen v. Evans (Mass.) 37 N. E. Rep. 571; Traute v. White (N. J. Ch.) 19 Atl. Rep. 196. What is said on the subject in this last case is purely dictum, and contrary to the Hunt Case, supra. The other cases we do not regard as binding upon us, even if it be conceded they hold to a contrary doctrine. Although, as we have said, there is considerable doubt as to the validity of the statute, yet it is not so plainly in violation of the constitution as to require an adverse decision. Plaintiffs are entitled to a judgment at law for the valúe or cost of one-half the wall.
8 The question remains, are they entitled to have a mechanic’s lien established against defendant’s property? It seems to us that they are not. When the defendant used and appropriated the wall, he became liable to pay plaintiffs one-half the value thereof under the statute, or, it may be, under his contract. But this was a mere personal charge, and could not be enforced by establishing a lien upon the land. Phillips, Mech. Liens, section 78, and cases cited. Moreover, the material was not *215furnished under a contract with the owner of the lot. There was simply an agreement to pay for material already furnished, or to be furnished at a subsequent time, and under other conditions than the mere furnishing of the material. Again, if the material was furnished under a contract with the owner, the statute of limitations is a complete bar to the action, for it must be brought within two years from the filing of the statement for the lien in the clerk’s office, and this statement must be filed within ninety days after the material shall have been furnished. Squier v. Parks, 56 Iowa, 407 (9 N. W. Rep. 324). Plaintiffs are not entitled to a mechanic’s lien, but they are entitled, under the allegations of their petition, to a judgment for one-half the value of the wall. — Reversed.