Abstract: A modular surface having an important use as a sports deck, and particularly for ball sports like tennis. The surface is built up of a number of generally square tiles in which the play surface is supported by a large number of support pegs intended to rest on an undersurface. The tiles are flexible so that the support pegs can remain in contact with the undersurface even if it is not perfectly plane, assuring consistent ball bounce. A special arrangement of expansion joints gears the ability of the tile to absorb expansion and contraction resulting from temperature changes to the geometry of the tile to: (a) keep the pegs on the ground even in the presence of temperature changes to assure consistent ball bounce, and (b) keep the play field itself from expanding or contracting without the need for anchoring it to the undersurface.