Yes, landscape fabric is an excellent and highly recommended material to use under a deck. Its primary purpose in this application is to stop weeds and unwanted grass from growing up through the gaps in the deck boards.
Landscape fabric also creates a tidy, low-maintenance surface, preventing the area from turning into a muddy, overgrown patch of ground. For this application, be sure to use a durable, permeable fabric and cover it with a layer of gravel or stone to hold it in place, block sunlight, and ensure proper drainage.
