A method for treating a plywood board, comprising - providing • a plywood board comprising a first and a second wood veneer layer, adhesive between the wood veneer layers (110, 120, 130, 140, 150), a first surface whose normal is unidirectional with the thickness (tp) of the plywood board, and a second surface opposite to the first surface; and • hydrofobizing agent, wherein • the first surface of the plywood board has been sanded or is sanded to a roughness which, expressed in Ra -value, is 2 μm or more; and - applying treatment agent comprising hydrofobizing agent onto at least the first surface of the plywood board, wherein - the first surface has a roughness, expressed in Ra -value, from 2 μm to 20 μm, - the treatment agent is an aqueous dispersion or emulsion of the hydrofobizing agent, - the hydrofobization agent is tall oil (such as crude tall oil or distilled tall oil), tall oil fatty acid, tall oil soap, or coniferous wood rosin, which may be chemically fortified, modified or saponified, and - the hydrofobizing agent is applied onto the first surface in an amount of 0.1 g/m 2 to 20 g/m 2 in said aqueous emulsion or aqueous dispersion, the method thereby comprising - applying hydrofobizing agent onto the first surface in such an amount that the moisture buffering value of the treated plywood board, measured according to the Nordtest guideline, is at least 0.5 g/(m 2 %RH). - providing • a plywood board comprising a first and a second wood veneer layer, adhesive between the wood veneer layers (110, 120, 130, 140, 150), a first surface whose normal is unidirectional with the thickness (tp) of the plywood board, and a second surface opposite to the first surface; and • hydrofobizing agent, wherein • the first surface of the plywood board has been sanded or is sanded to a roughness which, expressed in Ra -value, is 2 μm or more; and • a plywood board comprising a first and a second wood veneer layer, adhesive between the wood veneer layers (110, 120, 130, 140, 150), a first surface whose normal is unidirectional with the thickness (tp) of the plywood board, and a second surface opposite to the first surface; and • hydrofobizing agent, wherein • the first surface of the plywood board has been sanded or is sanded to a roughness which, expressed in Ra -value, is 2 μm or more; and - applying treatment agent comprising hydrofobizing agent onto at least the first surface of the plywood board, wherein - the first surface has a roughness, expressed in Ra -value, from 2 μm to 20 μm, - the treatment agent is an aqueous dispersion or emulsion of the hydrofobizing agent, - the hydrofobization agent is tall oil (such as crude tall oil or distilled tall oil), tall oil fatty acid, tall oil soap, or coniferous wood rosin, which may be chemically fortified, modified or saponified, and - the hydrofobizing agent is applied onto the first surface in an amount of 0.1 g/m 2 to 20 g/m 2 in said aqueous emulsion or aqueous dispersion, the method thereby comprising - applying hydrofobizing agent onto the first surface in such an amount that the moisture buffering value of the treated plywood board, measured according to the Nordtest guideline, is at least 0.5 g/(m 2 %RH).