Back Plastering. Back plastering consists of laying a coat of plaster upon laths which are nailed upon the inside of the outside boarding between the studs, and is frequently used in the outside walls of the better houses in the cold climates, as it adds much to the warmth of the building. Only one coat of low grade mortar with a little hair is necessary, but it must be well clinched and spread thickly, though it may be put on very roughly, as it is out of sight. It is not so expensive as it may seem at first, and the additional comfort with the resulting economy of fuel will repay in a short time the extra cost.