(a) Any judgment obtained under a claim made in accordance with this subchapter shall become a lien upon such structure and upon the ground upon which the same is situated, erected or constructed and shall relate back to the day upon which the labor was begun or the furnishing of material was commenced, or the time immediately following the time of recording of a first mortgage, or a conveyance in the nature of a first mortgage, upon such structure which is granted to secure an existing indebtedness or future advances provided at least 50% of the loan proceeds are used for the payment of labor or materials, or both, for such structure, whichever shall last occur.
(b) In the case of the erection, construction and filling in of wharves, piers and docks and improvements to land, the liens shall extend to the lots or lands in front of which improvements are made.