Yes, Welsh Green Slate can be used outdoors as it is a highly durable and weather-resistant material. This slate is commonly used for roofing, flooring, cladding, and paving in outdoor areas such as gardens, patios, and pathways. Its ideal for outdoor use due to its low water absorption rate, resistance to frost, and ability to withstand extreme temperatures. However, its important to ensure proper installation and sealing to ensure longevity and prevent damage.