Where the sheriff shall find that, in accordance with the law as at present existing, a church or manse must be built, rebuilt, or repaired, but the heritors shall delay or refuse to give effect to it, he shall remit to an architect or other professional person to prepare plans and specifications for such building, rebuilding, or repairs, and after hearing any objections thereto he shall approve of or modify the same, and ordain the same to be executed, and, if need be, he shall remit to an architect or other professional person to receive tenders for the execution of said plans and specifications, to accept of such tenders as shall seem best, and to superintend their execution; and the sheriff shall find the heritors who are now liable in the expense of such building, rebuilding, or repairs, and shall assess and allocate the same, together with a sufficient sum to cover the expenses of collection, upon them, according to their respective real rents, as these shall appear on the valuation roll or rolls in force at the date of such assessment and allocation, or according to their valued rents, as the case may be, and shall grant decree for payment thereof in such instalments and under such conditions as he shall direct.