Inspection and Preparation of the Screed

The premise for good behavior, durability, and reliability of a wooden floor is based on the characteristics of the substrate.

The screed must be provided:

• with adequate thickness

• flat

• hard

• without cracks

• clean

• compact

• dry

ADEQUATE THICKNESS

At least 4 cm for cementitious screeds, at least 2.4 cm for wood panel substrates.

If the passage of hydraulic, heating systems or other systems is planned, the respective pipes, adequately thermally insulated, must be incorporated into a screed of at least 6 cm in thickness, reinforced with electro-welded metal mesh to prevent cracks and settlements.

PLANARITY

Widespread irregularities in flatness and level differences in connections to other structures or construction types require smoothing interventions with leveling products.

HARDNESS

Anhydrite-based screeds, which are too soft, are not recommended, while cementitious screeds are recommended.

CRACKS

Expansion joints must be planned and implemented, in addition to structural joints which must be maintained and respected.

Any screed damage should be identified through visual inspection after thorough cleaning of the surface and must be repaired before leveling and flooring operations. Full-thickness cracking of cementitious screeds (resulting in detached plates) often necessitates the reconstruction of the subfloor. If the specified conditions are not fully met, flooring operations cannot be initiated.

Eporip by Mapei is a two-component solvent-free epoxy adhesive used for infilling and for monolithic sealing of cracks in screeds.

CLEANLINESS

Before consolidating the screed, clean it thoroughly by vacuuming dust. There should be no residues on the surface limiting or preventing the adhesion of adhesives and leveling compounds (it's important to remove residues of plaster, grease, oils, varnishes, and paints).

COHESION

After thorough cleaning, the surface should not "flake" under the scratching action of a metal tip. Primer is used to consolidate the screed. Mapei's Eco Prim PU 1K is a single-component hygro-hardening polyurethane primer used for surface consolidation of both cementitious and anhydrite screeds, including those with underfloor heating. If parquet installation is planned after 72 hours, apply Eco Prim PU 1K and sprinkle Quartz 1.2 from Mapei onto the still fresh primer until completely saturated.

MOISTURE

Residual moisture should be checked before laying floors using a calcium carbide device and must not exceed the maximum allowable moisture (2% in cementitious screeds).

For this reason, screeds laid on ground slabs, insufficiently ventilated voids such as those over open portico floors, must be isolated from their support plane with effective and durable waterproofing and a vapor barrier.

Eco Prim PU 1K from Mapei is a single-component hygro-hardening polyurethane primer, solvent-free, with very low emissions of volatile organic compounds (VOCs), used for consolidating and waterproofing cementitious screeds.

In any case, it is also advisable and economically negligible to always lay a layer of polyethylene under the screed, which guarantees a certain function as a vapor barrier, limiting water absorption to part of the area below, allowing the use of a low water/cement ratio without risking surface burning of the screed.

CEMENTITIOUS SCREEDS WITH UNDERFLOOR HEATING SYSTEMS

Screeds made with underfloor heating systems must be strictly "conditioned" by turning on the heating system itself according to a precise testing procedure before laying any type of flooring.

This operation aims to bring the structure to its final operating conditions, allowing any corrective actions (elimination of defects, deformations, etc.) that may be necessary.

Testing of the structure must adhere to the following rules:

The system must not be activated until 28 days after pouring

The temperature should be increased by 5°C per day until reaching the maximum liquid delivery temperature of the system

Maintain the maximum system temperature uninterrupted for at least 3 days

Decrease the temperature by 5°C per day until reaching room temperature

The heating must be turned off before laying the floors

Smoothing of the laying plane should begin 24 hours after the heating system is turned off, which can be turned back on 24 hours after installation.

Regardless of the type of substrate encountered, it is crucial to verify the presence of defects and notify the client in order to prepare appropriate correction measures.