N.C. Gen. Stat. § 45-69

Unless the security instrument provides to the contrary, if the maximum amount secured by the security instrument has not been advanced or if any obligation secured thereby is paid or is reduced by partial payment, further advances may be made and additional obligations secured by the security instrument may be incurred from time to time within the time limit fixed by the security instrument. Such further advances and obligations, together with interest thereon, shall be secured to the same extent as original advances and obligations under the security instrument, if the provisions of G.S. 45-68 are complied with.