Ronafix Pre-packed Underfloor Heating Screed is supplied as a pre-packed, ready to use mortar for laying floor screeds on underfloor heating systems. It is supplied complete as a bag of dry components and a bottle of polymer gauging liquid.

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• Features & Benefits
• Product Performance
• Mix Design
• Instructions for Use
• Preparation
• Joints
• Mixing
• Placing
• Curing

Features & Benefits

• Pre-packed factory formulated mortar
• Rapid strength gain
• Fast drying
• Faster commissioning of heating

Product Performance

Mix Design

• Portland cement CEM II 42.5: 50kg
• 0/4mm sharp sand: 150kg
• Ronafix Underfloor Heating Screed Admixture: 4.5 litres
• Water: up to 13.5 litres
• Yield per mix: 0.1m³ (approx)

Preparation

The insulation on which the Ronafix Pre-packed Underfloor Heating Screed is being placed must be suitable for floating floor screeds and for the thickness of screed to be laid.

Joints

Position isolation joints in doorways and around all perimeters and openings in the screed. Expansion joints for heated screeds should be positioned so that screed bays are no larger than 40m² with a length no greater than 8m, see BS 8204-1 Design Considerations.

If there are separate heating zones, they should be divided by expansion joints.

Screed bay joint proportions should ideally be 1:1 length to width and should not exceed 1.5:1. Long narrow bays should be avoided because of the risk of stress relief cracking.

Mixing

Ronafix Pre-packed Underfloor Heating Screed must be mixed by forced action mixer such as a Baron or CreteAngle mixer. Free fall mixers must not be used.

Mix for approximately 3 minutes. Over mixing will entrain air which may reduce performance. Once mixed the mortar should be used as quickly as possible.

Placing

As soon as the mortar is mixed, it should be placed onto the substrate, compacted, ruled and closed with a float or trowel. Avoid overworking the surface, this will increase the tackiness of the mortar. The float should be regularly washed, to prevent build up of polymer/cement paste.

Thicker screeds may be applied in two layers, wet on wet to aid compaction. Layers should be of approximately equal thickness. The base layer should be raked after compaction. To ensure satisfactory adhesion the lower layer should be raked to provide a key for the next layer. Should an intermediate layer begin to harden, a priming coat must be applied before application of the next layer.

Curing

Curing must commence as soon as possible after finishing the screed. Cure the screed with tight fitting polythene, placed on to the screed as early as it is possible to do so without damaging the surface. Cover for 24 hours then remove and air cure.