Ronafix Underfloor Heating Screed Admixture is a liquid polymer admixture which provides a high strength screed. The increased strength of the screed allows it to be laid in thin section, from 40mm, which in turn ensures improved thermal output from the underfloor heating system saving money on energy consumption.

Screeds containing Ronafix Underfloor Heating Screed Admixture also dry faster than conventional sand : cement screeds meaning the commissioning process can begin earlier (after only 7 days) and can also be opened to foot traffic after 24 hours.

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

Features & Benefits

• Thin section—from 40mm
• Faster commissioning of heating
• Improved thermal output—heats up much quicker than traditional screeds
• Can be walked on after only 24 hours

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 Underfloor Heating Screed Admixture 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 Underfloor Heating Screed Admixture 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. The screed mix must be well compacted, levelled and finished using a suitable float.

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.