rather than a conventional domed section used in prebuilt fireplaces one aspect of applicants 39 design includes a flue assembly which permits the use of a flat top design so that the overall height of the fireplace is reduced prevents spillage of combustion gases into the room and leads to economies both in manufacture and installation top wall 22 of combustion chamber 20 has flue 31 mounted on its upper surface in surrounding relation with flue outlet opening 32 formed therein and is positioned equidistant between side walls 24 24 39 but is offset rearwardly along the center line of the combustion chamber flue assembly 30 includes flue 31 diverter plates 33 33 39 and screen rail 34 transition section 26 is mounted to flue 31 to provide a connection between the chimney not shown and combustion chamber 20 as illustrated in fig2 a pair of diverter plates 33 33 39 are mounted in combustion chamber 20 and are shaped in the form of an 34 l 34 the angle formed by the two sides of the 34 l 34 is approximately 45 degrees the lower leg of which adds structural stability thereto diverter plates 33 33 39 are mounted perpendicular to top wall 22 and side wall 24 24 39 and in offset relation to rear wall 23 with the free end of diverter plate.