Occasionally a wood-framed house is back-plastered for warmth. This process consists in nailing a strip of seven-eighths inch furring against the inside of the boarding on each side of the studs. The space between the studding is then lathed (of necessity a slow and bothersome job) and plastered one rough coat of hair mortar, which should be allowed to dry before any lathing is placed over it on the inside face of the studding. As a matter of practice, the efficiency of back plaster is much injured by the fact that the studding, in seasoning after the plaster is set, is likely to shrink away from the plaster, leaving a narrow perpendicular crack on each side of the stud, which permits of the passage of cold air.