One renovation example would be a cost sharing the bathroom wall in which you'd lose a closet or relocate it elsewhere, but gain the needed space to accommodate the new design. This renovation is rather economical. One additional expense would be if there is hvac or electrical wires that would have to be relocated. Also if in this renovation the existing plumbing has to be moved. In all renovation, it's safer to install plumbing on the inside of the walls rather than the exterior. To protect from freezing. It pays to follow the advice of an experienced contractor who has learned not to plumb an exterior wall. The slightest gap, crack, or opening in the wall installation or inadequate volume of insulation protecting the water lines can cause them to freeze, and possibly crack, or even burst causing significant damage, obviously.