A wick heater comprises a housing the top and front panel of which are so constructed and interrelated with each other and the remainder of the housing to provide for their relative expansion and contraction in a manner to avoid warping, buckling or distortion or any undue stress on the housing or its component parts during operation of the heater. The top of the housing comprises a frame and inserts, a principal insert being interconnected with and for expansion and contraction relative to the frame and to position directly above the chimney of the heater and the area encompassed by its backing heat reflecting surface. This principal insert has a unique pattern of slots the bounding edges of which are flanged and a portion of which are oriented in directions at right angles to other of said slots to lend both strength and stress accommodation to the top of the housing. The front panel structure has a slip fit relation to the housing and is connected to the remainder of the housing only in an area adjacent its base. It also has a distinctive profile and mounts a guard the nature, character and interrelation thereof is such to add an important element of safety in use of the heater. The heater has numerous improvements providing a total construction which lends itself to a distinct moderation of the surface temperature of the heater housing.