An existing flame heat transfer fire testing apparatus was used to study the upward flame spread potential of two kinds of wall materials: (1) PMMA (Polymethylmethacrylate) and (2) Douglas Fir Particle Board. PMMA is noncharring whereas Douglas Fir Particle Board is a charring material. Various levels of external radiant heat flux ranging from 1.8 W/cm2 to 3.4 W/cm2 were imposed onto the wall samples in order to measure the flame heights as a function of energy release rate. Flame height measurements were established visually by a review of video recordings. The results for these wall flames correlate flame height to the 2/3 power of energy release rate per unit sample width. The wall results are generally higher than data from gas burner line fires against a wall for a range of 10 to 200 kW/m.