For a curling membrane under a floated mortar bed in a dry area, which material is recommended?

Using 15-pound tar paper for a curling membrane under a floated mortar bed in a dry area is recommended due to its properties that contribute to moisture control and overall stability. Tar paper acts as a moisture barrier, preventing the passage of any potential moisture from the substrate into the mortar bed, which can otherwise lead to curling or other damage over time. Its durability and resistance to the elements enhance the longevity of the flooring system, providing a protective layer that helps maintain the integrity of the installation.

In addition to moisture protection, 15-pound tar paper is relatively easy to install and is designed to provide a good separation between the mortar bed and the substrate. This separation is crucial, as it reduces the risk of any bonding issues that might arise from direct contact with the underlying surface.

While other materials exist, they may not provide the same level of effectiveness or compatibility for this specific application. For instance, plastic sheeting can trap moisture and may not allow for the necessary breathability of the substrate. Roofing felt typically serves a different purpose in roofing applications, and fiberglass matting may not be suited for this type of interior flooring installation due to its different composition and intended use. Thus, 15-pound tar paper stands out as the optimal choice for a curling membrane in