massetto

Massetto is an Italian term for a layer of cementitious mortar laid on a substrate to create a level surface for floors, pavings, or as an underlayment for finishes such as tile or wood. It serves as the final leveling bed in many interior and exterior flooring applications and can also contribute to the overall structural performance when combined with insulation or heating systems.

Composition and variants

A typical massetto is made from cement and sand, with possible additions of lime or gypsum and various admixtures to modify workability and curing. Common variants include: cementitious massetto (massetto cementizio), lime-sand massetto (massetto di calce), and gypsum-based screeds. Lightweight or insulating screeds use lightweight aggregates to reduce weight and improve thermal performance. A floating massetto (massetto galleggiante) is laid on an insulating layer and not bonded to the structural slab to reduce crack propagation and improve acoustics.

Thickness and finishing

The thickness of a massetto varies with use and load, but interior floors typically receive about 4 to 6 centimeters, with greater thickness for heavy loads or underfloor heating. After placement, the surface is leveled (rasato) and allowed to cure properly before applying final floor coverings. Proper curing, moisture management, and joint details are important to prevent cracking and debonding.

Applications and considerations

Massetto is widely used for indoor floors, including bathrooms, kitchens, and living areas, as well as for exterior terraces where appropriate drainage and weather resistance are ensured. Substrate preparation is essential: surfaces must be clean, dry, sound, and free of laitance; moisture barriers or primers may be required, and expansion joints are often integrated to accommodate movement.

Massetto thus functions as a versatile foundational layer in modern flooring and paving systems.