Polymer Modified Screed

Polymer modified screed is used in certain applications, usually where rapid drying is required, laid to falls or heavily trafficked areas. Ardex A29 is the most popular choice of product in this application.  We utilise additional products depending on the type of job and building.  

The floor beneath the insulation should be clear of debris that may affect proper placing of insulation. Voids underneath or between sheets of insulation should be avoided. Place suitable insulation onto structural floor, mechanically fix insulation if required. Install edge insulation, along the perimeter of the walls and columns, this to avoid cold bridging and allow the floating floor to expand.

Before placing of underfloor heating pipes and/or in advance of laying screed, a layer of minimum 500 gauge plastic membrane must be installed directly onto the insulation boards/poured floor insulation, and returned up the walls. This ensures no leakage of the screed and allows the screed to dry consistently throughout. Joints need to be taped and upturns and fixed at 150mm above screed levels. (It can be trimmed back after screed is poured.) Note the plastic membrane must be laid regardless of whether you are using under floor heating or not. See the link here to our preparation guide video.

Under floor heating pipes can now be placed over plastic sheeting and fixed at 500mm centres. Pipes are placed and fixed to the insulation boards using clips and/or rails. Fixings need to be no more than 500mm apart and extra fixings are required for bends/returns, to ensure pipes don’t float during screed application. Heating pipe system should be put on test while screed is being placed to ensure any pipe failure can be identified. (Discuss with your heating contractor.)

Avoid leaving any debris that may float to the surface of the screed, vacuum clean if necessary. Before screed placement commences, we set adjustable tripod depth gauges set by laser level to agreed datum, which is usually calculated from your door threshold, there is no requirement for datum lines on walls. This ensures a level floor throughout the building. Area for screed should be weather proofed, i.e. roof sealed, windows fitted and in dry condition. Ideally internal plastering of walls should be completed. Exact quantity of screed required can be determined when tripods are set on site using datum given. (There may be an additional charge for material used.)

Immediately after installation, it is important to keep all windows and doors closed to protect the surface of the new screed from frost, direct sunlight, wind, rain and water ingress for the first 7 days.

After 7 Days, windows and doors can be opened intermittently to remove surplus moisture by means of draught free ventilation. Failure to do this will prevent the screed for drying effectively.

Typically, the screed is ready to receive foot traffic after 24-48 hours after normal drying conditions.

A moisture test is advised prior to laying floor coverings. This service can be carried out free of charge by Ardex if you choose to use Flowplus screed or other Ardex products.

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