Sikafloor®-421 Therm Screed

Cementitious mixture and EPS beads

12 months from manufacture date

Store properly in original, unopened and undamaged sealed packaging in dry conditions at temperatures between +5 °C and +30 °C. Protect from direct sunlight.

Adhesion to Concrete

+6 °C min/ +40 °C max.

+6 °C min/ +40 °C max.

60 - 120 min

Approx. 100 Litres

equivalent to 100 mm thick/m²

The substrate must be clean, sound, dust free without any traces of oil, laitance, curing compound and other contaminants. The substrate must be fully cured and is sound enough to receive the weight of Sikafloor®-421 Therm Screed.

Deeply contaminated substrate must be abraded to clean and sound surface.

Pan Mixing

• Mixing blade should be about 2 mm above the base of the drum.
• Pan mixer with a minimum capacity of 150 Ltr is required for mixing.
• Prepare a clean empty container and pour in 80% of the required water.

• Pour the Sikafloor®-421 Therm Screed powder into the container, use the hand mixer to mix until a homogenous slurry is achieved. Small quantity of EPS beads can be added to ease the mixing.
• Load the remaining EPS beads followed by the slurry into the pan mixer.
• Start the pan mixer and mix continuously for 5 – 10 minutes until homogenous consistency is achieve. Remaining 20% water can be used to adjust the consistency of the mixture.

Hand Mixing

• Prepare a flat bottom container with 75 Ltr capacity.
• Pour 80% of the required water into the container.
• Pour in Sikafloor®-421 Therm Screed into container and start hand mixer to mix until homogenous slurry is achieved.
• Pour the EPS beads into the container and mix until a homogenous consistency.
• Ensure that the hand mixer is moved around to have proper mixing.
• Remaining 20% water can be used to adjust the consistency of the mixture.

IMPORTANT: If mixing in partial batches, ensure the measurement of powder, EPS beads and water ratio are accurate.

Primer

Prime with a slurry scratch coat/key coat by mixing Davco 751 with cement and fine sand at 1:1:1 ratio. Apply a thin coat to form key coat.

Pour the light-weight insulation screed onto the primed substrate, apply it wet to wet to the key coat. Then use a straightedge to level-off the screed to the required thickness and levels. (Max. Thickness 100 mm)

Additional layers: Allow the previous layer of lightweight screed to cure for up to 7 days or until it cures.

Apply another layer of primer and leave it to dry before adding the additional layer of lightweight screed.  
 

Sealing layer (Optional): After the insulation screed has hardened, use a steel trowel to smoothen the surface with a sealing layer Sikafloor®-412 Level FR @ 10 mm thick).
 

Concealed roof: Apply Sika waterproofing solution (liquid or sheet membrane) according to the related Sika Method Statement.

- Pour the lightweight insulation screed directly on top of the waterproofing layer. Then use a straightedge to level-off the screed to the required thickness and levels. (Sarnafil PVC membranes must be protected with a layer of geotextile).

- Sealing layer. After the insulation screed has hardened, use a steel trowel to smoothen the surface with a sealing layer. After the sealing layer has hardened, it is recommended that induce/control joints are saw-cut at the required intervals base on engineer’s requirement. Seal the joints with Sika approved sealants.
 

Lightweight floor underlayment

Leave the final layer of lightweight screed to cure for 24 hours.

Apply a slurry key coat using Davco 751 onto the lightweight screed. Then apply al ayer of 20 mm Davco Floor Screed before application of tiling, carpet or parquet work. A   Use Sika approved tile adhesive or levelling compound.

Protect the lightweight screed from early hydration using a blanket wet hessian

• Clean mixing and application equipment with water immediately following use.
• Remove splatter or spills with water before material sets.