It is necessary to consider the possible expansion by providing a gap when particleboards were used as wall sheathing. This study discussed the change of expansion gap of panel wall sheathing at different relative humidity. The results showed that decorative and edge sealing UF particleboards could be used as wall sheathing in humidity condition such as kitchen, and non decorative panels were not suitable for wall sheathing directly. It was also concluded that the suitable expansion gap of particleboard wall sheathing was about 2～3 mm per meter length of wall.