STP untreated knotty spruce panel. The untreated panel can be treated in many ways according to your own wishes. Please note that there might be wastage. Before installation the product must have the same moisture ratio and temperature as the space where it is going to be installed in. This reduces possible expansion caused by changes in temperature and moisture. This takes about 3-4 days. The installation is easy and due to the short length of the panels you can even do it by yourself. The panel can also be used in humid spaces.