Moisture distribution through the thickness of plywood is analyzed when the sheet is subjected to different relative air humidity from both sides using one dimensional diffusion equation. The shape change of plywood sheet is numerically analyzed when moisture influence from both sides of sheet is not time – dependent, and also when one side of the sheet is subjected to time-dependent outside moisture-temperature conditions and conditions on other side is not time-dependent. The outdoor moisture-temperature conditions were taken form national standard LBN-003-01 “Būvklimatoloģija” and approximated with third order polynomial using its average values summed with average amplitude.