delivered the opinion of the Court:
The acts of Congress are not important in this connection, since no attempt has been made, either by Congress or the commissioners of the District of Columbia, to enact a law or an ordinance legalizing the erection of party walls. It may well be that the acts of Congress only conferred power upon the commissioners to regulate the construction of party walls where authorized under existing conditions. In other words, wherever party walls were authorized to be constructed within the limits of the original city, or by contract of the parties outside of said limits, the Commissioners by proper regulations should prescribe the kind of materials to be used and the size, form, etc., of the proposed structure.
The building regulations of the District of Columbia in respect of party walls rise neither to the dignity of statutes or ordinances. They are mere rules for the enforcement of existing rights, established, in this instance, by the order of President Washington, expressly authorized by the provisions of the original grant. The order of the President was necessary, in conjunction with the terms of the grant, to establish this perpetual easement or servitude upon all of the lands embraced within the original city. Being contractual, no legislation was necessary either for the enforcement or the enlargement of the right. Neither Congress nor the commissioners of the District have ever attempted to extend the original party wall regulation promulgated by President Washington. Duties have been imposed from time to time upon the-surveyor and inspector of buildings in regard to supervising the construction of party walls; but these can only be interpreted as applying to legal party walls, or such as existed within the original city or by *356convention of the parties. Indeed, the last building regulations adopted by the commissioners of the District (October 18,. 1909) contain the following provision: “Sec. 62. The 4th section of the building regulations, No. 1, approved by President Washington, October 17, 1791, quoted below, is recognized as in force, and is published for the information of builders. The inspector of buildings has no official duty as to the enforcement of this regulation, as the matter is one of private rights between parties.” Referring to the regulation of President Washington, Mr. Justice Cox, in Fowler v. Saks, 7 Mackey, 570, 579, 7 L.R.A. 649, said: “This building regulation, so authorized, is the foundation and the only source of-the right claimed by any one here to locate his party wall one half on his neighbor’s land.”
There are but two lawful ways in which a party wall can be established, — (1) by contract between the owners of the adjoining properties, and (2) by force of statute. The limitation is well expressed by Justice Cox in Fowler v. Saks, supra, as follows: “What we understand now by a party wall had no existence at common law, except by convention between co-terminus proprietors. A man had no right to enter upon and occupy a part of his neighbor’s land for his own convenience, or for any purpose whatever, without his consent. The privilege or easement, as we call it, giving to a builder the right of erecting a division wall between himself and his neighbor, partly upon his neighbor’s land, is therefore purely the creature of legislation.”
It follows that the right conferred by the regulation of President Washington is one purely in contract, imposed by the condition in the original, grant. Referring to this regulation, Chief Justice Cranch, in Miller v. Elliot, 5 Cranch, C. C. 543, Red. Cas. No. 9,568, said: “It is, therefore, a condition annexed to the title of every house lot in the city of Washington, that when the proprietor builds a partition wall between himself and his neighbor he shall lay the foundation equally upon the lands of both; and that any person who shall afterwards use the partition wall, or any part of it, shall reimburse to *357the first builder a moiety of the charge of such part as he shall use.”
We now come to the more difficult questions involved in the present case. The erection of a party wall by one of the two adjoining owners does not, we think, amount to a taking of private property for private use, in the broad sense of the limitations of the Constitution. It amounts only to the establishment of a mutual easement or servitude and benefit. Of course, in the absence of statutory or contractual authority, such a servitude may not be imposed. .But, as we shall observe later, it may, under certain conditions, be maintained, though constructed without either statutory or express contractual authority. The erection of a party wall does not change the boundaries nor affect the title of the respective properties. While it stands, each party is permitted to use the wall. The right to its use and enjoyment passes with a conveyance of the properties, and when, for any reason, it ceases to exist, the rights of the respective owners stand as originally.
At common law7 it was defined as a wall of which two adjoining owners are tenants in common. Watson v. Gray, L. R. 14 Ch. Div. 192, 49 L. J. Ch. N. S. 243, 42 L. T. N. S. 294, 28 Week. Rep. 438, 44 J. R. 537; Cubitt v. Porter, 8 Barn. & C. 257, 2 Mann. & R. 267, 6 L. J. K. B. 306. In this country, many of the States have adopted the rule that the owners of a party wall erected in part upon the land of each are not tenants in common of the wall, but are owners in severalty of the part standing upon his land, subject to the easement of his neighbor for its support and the equal use thereof. In other words, the owners of the adjoining lands upon which the w7all is constructed are neither joint tenants nor tenants in common of the wall, but each owns the soil in severalty up to the dividing line, as well as that portion of the wall resting upon it, and the soil of each, with the portion of the wall belonging to him, is burdened with the easement and servitude of support in favor of the other. Hoffman v. Kuhn, 57 Miss. 746, 34 Am. Rep. 491; Fidelity Lodge, No. 59 I. O. O. F. v. Bond, 147 Ind. 437, 45 N. E. 338, 46 N. E. *358825; Everett v. Edwards, 149 Mass. 588; 5 L.R.A. 110, 14 Am. St. Rep. 462, 22 N. E. 52; Bellenot v. Laube, 104 Va. 842, 52 S. E. 698.
Undoubtedly this wall, like thousands of others in the District of Columbia outside of the limits of the original city, was constructed in the belief by the owners of the adjoining lots that the builder was authorized by law to construct one half of the wall on the land of his neighbor. A custom so universally acquiesced in will go far toward composing any equitable or legal differences which may arise in the future over party walls now in existence, and which were constructed without express contractual authority. It is a matter of common knowledge that the officials of the District, in the enforcement of the building regulations, require plans of the buildings to be filed in the office of the inspector of buildings, and permits to be issued, and that general supervision is exercised over the construction of buildings in the District as to the quality of materials, relation to the street and to surrounding buildings, plan of structure, etc. It is also a matter of common knowledge that in many instances rows of houses connected by party walls have been constructed by the same owner, and subsequently sold in this condition. And it may be that additions have been laid out by a single owner with express provision for the construction of party walls between the lots of coterminus owners.
In the present case, however, plaintiff constructed the wall in question, one half on the adjoining lot, so far as appears from the record; without either statutory or express contractual authority. It is well settled that, where an owner of the lot on to which a party wall extends accepts the wall by attaching his building thereto, he estops himself to complain of the trespass; and the mutual easement or servitude is as completely established as if the wall had been constructed under the authority of a statute or an express contract. We think the same rule will apply where the owner of an adjoining lot has notice of the construction of a party wall, partly upon his land. If he stands by, and, without protest, permits the erection of the *359wall to proceed to completion, the law will imply an agreement on his part to accept the benefits thus tendered.
Assuming that no express or implied agreement existed between the adjoining owners at the time of the erection of the Avail in question, can defendant, the grantee of the original OAvner of lot 103, be required to contribute to plaintiff for the portion of the wall appropriated by her in the construction of her house? It is alleged in the declaration, and admitted by the demurrer, that she purchased lot 103 “subject to the condition that no structure should be erected thereon, except such as are allowed in the city of Washington under the building regulations, and with knowledge of the existence of the aforesaid wall as built and located as hereinbefore described, and that shortly thereafter she commenced the construction and building of a dwelling on said lot . . ., and in doing so she used said party wall as such and as the east Avail of her said dwelling, and for its support made use of said party wall so as aforesaid built by the plaintiff, in the usual and customary manner, placing or anchoring the joists and supports of her, the defendant's aforesaid dwelling, therein and thereon, and she still continues to so use and occupy said wall; that she has not paid for such use of said wall the value thereof as ascertained and certified by the building inspector of the said District.”
There is reputable authority to the effect that a person who uses a party wall, by the acceptance and appropriation of the wall and the use tendered by his neighbor in its construction, becomes liable for the Auilue thereof, though neither he nor his vendor was a party to the erection of the Avail, and made no agreement, express or implied, concerning it. Spaulding v. Grundy, 126 Ky. 510, 13 L.R.A.(N.S.) 149, 128 Am. St. Rep. 328, 104 S. W. 293, 15 Ann. Cas. 1105; Sanders v. Martin, 2 Lea, 213, 31 Am. Rep. 598. On the other hand, the majority of the courts in this country adhere to the hard and fast rule of the common law that a person dispossessed becames absolutely entitled to all improvements made without his request and sanction, without -paving for them; and whether the entry is tortious or in good faith, the rule is the same. Antomarchi v. *360Russell, 63 Ala. 356, 35 Am. Rep. 40; Sherred v. Cisco, 4 Sandf. 480; Orman v. Day, 5 Fla. 385; Allen v. Evans, 161 Mass. 485, 37 N. E. 571; Griffin v. Sanson, 31 Tex. Civ. App. 560, 72 S. W. 864; List v. Hornbrook, 2 W. Va. 340.
Were this an isolated case and of no public importance, AA?e might be inclined to the latter vieAv. But buildings in large sections of the District of Columbia have been constructed in accordance Avitk an established custom that, where the OAvner of a lot upon Avhick a party Avail has been constructed connects his building to it he should pay his neighbor the value of the portion of the Avail used. This custom Avas extended outside of the limits of the original city, probably in the belief that the regulation of President Washington Avas in force throughout the District of Columbia. The enforcement, as to walls now in existence, of the custom thus established, will tend to uniformity throughout the District; and for that, if for no other reason, the court should hesitate to adopt a stricter rule Avhich might result in much confusion. For AA'hatever source it may have originated, the custom, when tested in the forum of conscience, is so heavily fraught Avith justice and equity that no possible evil can result from its adoption. In Spaulding v. Grundy, supra, where this exact question was under consideration, the court said: “But back of this, there stands out in SAipport of appellants’ claim the substantial fact that appellee has appropriated to his own use a part of this party wall errected by appellants’ vendors, without having paid anything therefor. So that, aside from any of the distinctions that involve the laAv of party walls in obscurity and doubt, there remains the proposition, strongly put in behalf of appellants, that justice and fair dealing demand that appellee should contribute toAvards the payment of a wall that he has used to his advantage and benefit. Indeed, it might with propriety be said that the question here involved partakes more of the nature of a suit for contribution than one involving the doctrine of party walls. Placing the case upon this ground simplifies very much the question to be disposed of. We need not inquire into the law concerning covenants running Avith the land, as it bears upon the questions *361of party walls; nor is it necessary to attempt to reconcile tlie conflicting decisions touching the rights of remote vendees in respect to them. There is authority, founded in reason and justice, that requires a person who uses a party wall, in the absence of any agreement or contract, to contribute his fair proportion of the cost thereof to the person erecting the wall, or, to put it in another and perhaps a better way, to pay a reasonable price for the use of the wall.”
We come now to the right of plaintiff to recover under his reservation in the deed. The construction of a party wall creates a mutual servitude which permits the owner of one of two adjoining properties to build one half of his wall upon the property of his neighbor. Such a servitude had been established in this case. Hence, when plaintiff sold his property, the servitude imposed upon the adjoining property passed to the purchaser, as the property could not be used and enjoyed by the purchaser without the full servitude. It follows that the reservation in the deed could not reserve a right which the purchaser acquired in the premises, including the portion of the wall standing upon the land of his neighbor. The whole servitude, of necessity, must pass to the vendee. In Duperreault v. Roy, Rap. Jud. Quebec 29 C. S. 343, where the reservation was the right to the common use of the wall, the court, sustaining the right of the vendor to collect from the adjoining owner the value of one half of the wall, said: “Then the reserve of the droit de mitoyennete [right to the common use of the party wall] could not have reference to the servitude of the property sold over the other property, for that was clearly and necessarily conveyed by the sale of the house as it stood. And yet the vendor must have sold something that belonged to himself. It follows, then, that he could not have sold the servitude of the neighbor’s property over his property, as that did not belong to him. That servitude enabled the neighbor to make use of the wall which the vendor had built for the purpose of supporting a house which would be built on the neighbor’s property; that servitude was not by any means in the control of the vendor of the house, but was a servitude which the law gave from *362public motives to the neighbor. What, then, did the vendor ,iu this case have that he could reserve % That is to say, what right could he have exercised, against his neighbor if ho had continued to hold the property. Clearly he could not have prevented his neighbor from using the wall which he had built and making it common; the neighbor did not even need to ask his consent for that purpose, but he did have the right to collect from his neighbor the one half of the value of the wall, when the neighbor chose to exercise his servitude of mitoyennete [joint property claims of two neighbors to a wall] upon the wall in question. That is the only thing which he had to reserve; that right was not a servitude, and was not a real right at all, but was a personal right, as the judgment below has found.” It was further held that the vendor could not reserve an interest in the wall, because “he had no property in the half of- the wall which rested on the land of the neighbor.”
The mere exercise of the legal right to place one half of the wall on the adjoining land created no title in it. It created in the builder of the wall a right to compensation for one half of its cost when the owner of the adjoining lot should elect to use it. The right to compensation is a mere personal claim, which the law establishes against the adjoining owner when he elects to use the wall; but it creates no interest either in the property or the wall adverse to such owner. In other words, the wall could only be common property between the owners of the two adjoining properties, in the sense that they had the mutual right to use it. Had the plaintiff become the owner of the adjoining lot, and desired to build, he could have used the wall under the reservation without compensation to anyone, for the right to compensation he had reserved. It follows that, not electing to exercise this personal right reserved to himself, he could enforce it against anyone else exercising it.
Th judgment is affirmed, with costs. Affirmed.