A damp protection arrangement for a space confined by floor, ceiling and wall portions in a building and comprising the following components: a damp permeable first layer structure (80), inside the space comprising at least one wall portion (16/80) of said portions; a second layer structure (60), inside the space covering at least the first layer structure (60/80); a continuous air gap (50), separated from the space and defined between the first and the second layer structures; an air inlet at a lower level in the space and communicating with the air gap (50); an air outlet at a higher level in the space and communicating with the air gap; and heating source (54) inside the air gap (50) for providing an air flow in the air gap between the inlet and the outlet and capable of dehumidifying layer structures.