Biohabitat solid wood walls, is made exclusively in solid fir wood, divided into multiple layers (vertical, horizontal and diagonal) to form the desired thickness (150, 180, 210 mm). The layers are joined together with wooden pins - also known as wooden dowels or stakes, without using nails or glue. The wood is dried naturally in the open air for almost 8 month, then in ovens, until a suitable internal humidity is achieved. The beech wood dowels are dried to a greater extent than the wood of the wall and then inserted with a pressure of 30 atmospheres into a hole smaller than the same dowel. This procedure ensures that, absorbing the humidity of the surrounding wood, the wooden dowel expands, thus remaining immobilized as if it was a branch that has grown naturally inside the boards. Between second end third layer of boards (internal side of the wall), a paper sheet is inserted with air tighness function.