The petitioners assign three grounds upon the basis of which they contend the judgment of the Superior Court should be reversed: (1) The hearing before the Board was based upon statements not under oath and those objecting to the special permit were heard by unverified petition and were not present for cross-examination; (2) the record of the hearing before the Board was not sufficiently comprehensive to permit the court to determine whether the Board had acted arbitrarily or had committed errors of law in denying the permit; (3) the standards set up by the Zoning ordinance are too vague and indefinite for the Board of Adjustment to follow in granting or denying a special use permit.
The appellants contend the Board of Adjustment in passing on a request for a special use permit must base its decision on testimony taken in an open hearing under oath “affording the parties the right to cross-examine.” For support they rely on this Court’s decision in Jarrell v. Board of Adjustment, 258 N.C. 476, 128 S.E. 2d 879. In Jarrell the zoning board was required to find as a fact whether on the day the zoning ordinance became effective the petitioner’s property was in use as a one family or as a two family unit — if a two family unit, the owner had the right to continue its use as such — if a one family unit the owner was in violation of the ordinance by using it for two families. The dispute presented a question of fact. The finding involved a property right. The courts are bound by the findings if supported by competent, material and substantial evidence. Obviously, when material findings of fact must be made on conflicting testimony, witnesses should be sworn. To that end G.S. 160-178 authorizes the chairman or acting chairman of the board “to administer oaths to the witnesses in any matter coming before the board.” However, by voluntary participation in a hearing, a party may waive the right to insist that the witnesses should be under oath.
The petition now involved is addressed to the discretion of the Board. The petitioners are charged with the duty of presenting facts sufficient to warrant the Board in issuing the special use permit. The petition was not verified. The petitioner, Mr. Craver, according to the minutes, presented a “plot plan,” explained in detail that his wife’s grandparents wanted to live near her in the summer, and return to Florida in winter. Mr. Craver was not sworn as a witness. He made no request that any of those objecting to the permit be *43sworn or that they be called for cross-examination. Mr. Craver, therefore, is not in a favorable position to complain that the objectors were not sworn and not available for his cross-examination.
The record discloses full discussions took place before the Board, participated in by Mr. Craver on behalf of the petitioners, and by Mr. Hines on behalf of those opposed. The proceedings were informal, made so by Mr. Craver’s lead, and continued in the same vein without his objection. The burden is on the petitioners to show merit in the application. If only sworn testimony may be considered, they offered nothing to support the application. The first assignment of error is not sustained.
The record shows that after the original proceeding Mr. Craver filed a request for reconsideration upon the basis of additional information set forth in the petition. That petition was not verified. The Board, after considering the new information in the request, denied a rehearing. The petitioner appellants even now do not allege they were denied opportunity to present any and all facts pertinent to the inquiry. The Board’s minutes show the Board considered all matters presented and, in its discretion, denied the application. The petitioners, having invoked the jurisdiction of the Board, are not in a position to challenge that jurisdiction. Convent v. Winston-Salem, 243 N.C. 316, 90 S.E. 2d 879. The petitioners’ second assignment of error is not sustained.
It is difficult to understand why and for what purpose the petitioners challenge the zoning ordinance as being too vague and indefinite to be followed “in granting or denying a special use permit.” If the provision for such permit is void for indefiniteness, then the Board is without authority to issue it and the petitioners are subject to the terms of the ordinance, which does not permit the use. A special permit is not a legal right but is a concession in exceptional cases which the Board, in the exercise of its discretion, may grant, subject to court review. G.S. 160-178; Austin v. Brunnemer, 266 N.C. 697, 147 S.E. 2d 182; Schloss v. Jamison, 262 N.C. 108, 136 S.E. 2d 691; In Re Pine Hill Cemeteries, Inc., 219 N.C. 735, 15 S.E. 2d 1. The petitioners’ third assignment of error is not sustained.
The judgment of the Superior Court is
Affirmed.
Moore, J., not sitting.