Opinion by
Mr. Chief Justice Mitchell,The east wall of complainants’ house, which is the subject of this litigation, is a party Avail, and is left as it Avas, presumably sufficient for the building. The defendant did not intend to make any use of it at all in his neiv building and has not done so. His oavii wall is twenty feet away and the excavation for his cellar is entirely on his own ground. Unless, therefore, his position and duty are altered by recent legislation which Avill be referred to later, he owed the wall no duty Avhatever except to dig his cellar without negligence. Whether it Avas dug ten inches or ten feet from the party line Avas no one’s concern but his oivn so long as he used due and proper care in the digging. The right of lateral support Avhich is absolute for land in its natural state extends no further than to the avoidance of negligence as to land incumbered Avith buildings.
On presenting his plan to the Bureau of Building Inspection, appellant Ai'as directed to underpin the party Avail, and to increase the thickness of the underpinning wall in proportion to the increased depth of his cellar excavation. No direction Avas given as to the location of the increased thickness, and appellant in complying with the order placed it inside the plaintiff’s line. This is the trespass complained of.
The authority of the inspecters to make such order is sought to be derived from section 24 of the Act of May 5, 1899, P. L. *378193. That section provides that the necessary alteration, whether repair of the old wall or building of a new one shall be made according to the inspectors’ decision and “ In every case where such wall or walls are defective, out of repair, or insufficient for the purpose of the buildings there existing upon the adjoining premises and using the same, the cost or expense of such repair or removal, together with the expense of the new wall or walls to be erected in lieu thereof, shall be borne and paid by the owner of said building upon the adjoining premises and the party erecting the new building in proportion to the amount of such wall or walls which is or shall be respectively used by their said buildings; and in every case where such wall or walls are defective, out of repair, or insufficient only for the purpose of the new buildings, the cost and expense of such repair or removal, together with the expense of the new wall or walls to be erected in lieu thereof, shall then be borne and paid exclusively by the parties erecting the new building.”
Concisely'stated this section provides for two classes of cases, first, where the alteration is for the benefit of both parties owning and using the buildings of which the old wall is part; and, secondly, where it is only for the benefit of the owner of the new building. The present case does not come under either class. It does not appear in the case what was east of the east wall of plaintiffs’ house before the alterations began, but it is found as a fact that said wall was a party wall and there being no evidence to the contrary presumably it was and is sufficient for its .joint use as such. But class first of the section contemplates a continued joint use, and as defendant has not made any present or contemplated any future joint use of the wall, the case is not within that class. Nor on the other hand does it come within the second class, for the new buildings have no connection whatever -with the wall. If defendant had simply built at twenty feet east from the line it is manifest that the question of the party wall would not have arisen at all in any shape. The controversy arises not from the new buildings, but from the, excavation of the cellar to a depth below the old wall. As the statute does not cover that case, the previous law remains in force and defendant owed the plaintiff no duty but to dig his cellar with proper care and without negligence.
*379Party walls are creatures of statute. In principle they are provisions for taking one man’s property for the private use of another; which, in general, is beyond the legislative power even for police purposes. They rest, therefore, on long recognition and acquiescence amounting to a settled constitutional construction. But rights claimed under them must be sustained by clear statutory authority. Whatever authority, therefore, the Bureau of Building Inspection had was by virtue of its general police power to provide against danger to the parties or the public. It clearly had no authority to order the appellant to put the increased thickness of the underpinning wall on his own land, nor did it do so. No statute authorizes the adverse use of more than ten inches of the adjoining owner’s land, and the order of time in building is in this respect immaterial. If plaintiffs had built first in such way as to require the additional thickness of wall they must have put all but ten inches of it on their own land. But the additional thickness in this case was altogether for plaintiffs’ benefit, appellant not using the wall at all and having no necessity for such thickness. The building inspector in ordering suoh additional thickness of wall as he deemed proper for public safety did not specify on which land it should be located, and the appellant assumed that it was to be on plaintiffs’. As it was for plaintiffs’ benefit and appellant could not be compelled to put it on his own land he was entitled to assume that it was to be on plaintiffs’. In view of the doubtfulness of the inspector’s authority to make such an order at all, it would have been more prudent for appellant to have called on the inspector to execute it, or on plaintiff to permit it to be done. This appellant claims to have done as will be next considered.
The evidence is clear that the additional thickness of wall on plaintiffs’ land is no detriment at present but a protection that they would have to build themselves if appellant had not done it for them. Nor is it any interference for the future, as, like any other building put on another’s land, it has become his and he can do as he will with it at any time. The building of it by appellant on plaintiffs’ land was a proper interpretation of the inspector’s order, and if it should be held that the order was 'beyond the inspector’s authority, the most that can be said of appellant’s action would be that it was a technical tres*380pass, done under supposed compulsion of law, clearly to the benefit of plaintiffs, and that nominal damages would be the utmost for which a recovery could in any aspect be allowed.
But even in the aspect of a trespass plaintiffs are not entitled under the evidence to damages, even nominal. The bill charged that defendant (a) in defiance of the building laws (b) secretly and unknown to the plaintiffs (c) committed a trespass. The answer set forth specifically (a) full compliance with the building laws, (b) knowledge and acquiescence by the plaintiffs in defendant’s action, (c) that there was no trespass. The answer was responsive and put on plaintiffs the burden of disproving it. This ivas not done. On the contrary, the weight of the evidence is clear that the plaintiffs not only must have known but did in fact know what was being done and tacitly if not expressly assented to it. Point is made that the plaintiffs being committee of a lunatic could not waive his rights. But plaintiffs, like any other trustees, are authorized within the limits of their trust to bind their cestui que trust by acts clearly for his benefit.
Decree reversed, injunction dissolved and bill dismissed with costs.