(1) In the cases governed by section 1163, the owners of the encumbered plots of land are jointly entitled to a blanket mortgage.
(2) Each owner may, unless otherwise agreed, demand that the mortgage on their plot of land be restricted, in accordance with section 1132 (2), to the partial amount which is equivalent to the proportion between the value of their plot of land and the value of all of the plots of land, and that it be allotted to them with this restriction. The value is calculated deducting those encumbrances that have higher priority than the blanket mortgage.