This fiber cement underlayment is installed over the subfloor to provide a smooth, water-resistant, durable surface in which porcelain or ceramic tile may be installed. It may also be installed for countertops in conjunction with tile. These products feature a dense, nonporous surface, making them excellent choices for kitchen and bathroom applications where moisture is a fact of life. The surface and edges are also smoother than those of competing products for easier installation and neater finished jobs.