(2)Where any such improvement was effected at the cost of the mortgagee and was necessary to preserve the property from destruction or deterioration or was necessary to prevent the security from becoming insufficient, or was made in compliance with the lawful order of any public servant or public authority, the mortgagor shall, in the absence of a contract to the contrary, be liable to pay the proper cost thereof as an addition to the principal money with interest at the same rate as is payable on the principal, or where no such rate is fixed, at the rate of nine per cent per annum, and the profits, if any, accruing by reason of the improvement shall be credited to the mortgagor].
