The behaviour of unsteady planar strong fountains, impinging on a ceiling with an opposing heat flux on the ceiling, is investigated numerically for 8.0 <= Fr <= 30.0 at Re = 50 and Pr = 7. The height of the ceiling is varied in 10 <= H/X-in <= 25, where X-in is the half-width of the fountain source, and the non-dimensional gradient of the temperature difference between the fountain source and the ceiling is varied for 0.2 <= Delta 0/(H/X-in) <= 1.8. It is found that the fountain does not hit the ceiling, but instead stagnates and spreads at some distance from the ceiling due to the stratification of the fluids in the immediate vicinity of the ceiling. The scaling and direct numerical simulation results show that the augmented spreading distance H-d + X-d has the scaling of H-d + X-d similar to XinFr2/9(H/X-in)(1/2)[Delta 0/(H/X-in)](- 1/3) in the range studied, where H-d is the maximum fountain height, X-d is the spreading distance measured at H-d, respectively. (C) 2009 Elsevier Ltd. All rights reserved.