The increasing use of cement mortars over plywood substrates and in high-rise buildings has demanded new performance requirements of these mortars to overcome dimensional movement in these substrates. A -10°C Tg, glass transition temperature EVA redispersible polymer powder is compared to a +10°C Tg" redispersible, EVA polymer powder for flexural, compressive and tensile strength in a standard three to one sand to cement mortar. Both polymers are also compared for plywood adhesion and flexibility in a standard thin-set formulation. It was found that the -10°C Tg polymer gave increased plywood adhesion at higher levels of modification and superior flexibility while still maintaining comparable strength properties to the +10°C Tg polymer. This would indicate that a -10°C Tg EVA redispersible powder will be better able to bridge gaps in a subfloor as well as allow for subfloor movement due to settling or expansion and contraction due to its better flexibility.