Liquid Screed Tile Guide
Many issues have been raised in the past about Calcium Sulphate Screeds when it comes to fixing the final floor covering.
The same problems happen to traditional sand and cement screed as well.
Results from an independent test found that a 50 mm Screed with good airflow and ambient temperatures of 20 degrees could dry within as little as 25 days.
The test results commissioned by Gypsol are found here.
The British standard guide is all screed dries at 1 mm per day and 2 mm per day above 40 mm.
If the building has no windows open how can the moisture escape?
When the windows have to be kept closed then dehumidifiers should be used.
Removal of surface laitance is very important.
The Screed will have a film of laitance once it has dried, this can be removed by brushing between 18-36 hours
If the surface of the screed has any loose material for example plaster, this will need to be removed by mechanical means.
An orbital floor sander is the best method for achieving this.
All screeds require priming with a suitable acrylic primer. This is done to stop the adhesives drying too quickly, so maximum strength is obtained.
If Cement based adhesives are to be used the floor will need priming until screed is no longer porous.
Anhydrite based adhesives generally only require 1 prime. We can recommend a complete range of adhesives for fixing wood or tiles.
You can run dehumidifiers after 7 days. This must be done in a closed loop so the building must be sealed from the outside completely.
You can also run the underfloor heating through a full heat cycle to dry the screed.
The use of a temporary electric boiler is the best way to dry the screed allowing construction to be completed without delay.
Please speak to one of our team if you would like to hire a boiler.
Force drying of liquid screed can be accomplished by commissioning of underfloor heating systems in accordance with BS1264: 2001 Part 4 clause 4.4 as early as 7 days after the screed has been placed.
The screed must be dry before application of the floor finish and failure to follow this procedure prior to the application of subsequent impermeable floor coverings such as tiles is likely to lead to failure of the floor finish at a later date. Subsequent to drying the screed by one of the above methods the residual moisture content must be determined using one of the approved test procedures to demonstrate suitability for acceptance of floor finishes.
Once proven to be dry it is important that the surface of the screed is not subjected to any spillages or leaks eg. plastering water buckets. Should these occur the exposed screed will require further drying to attain the required moisture content and in the worst case, full saturation of the screed drying times will be as with freshly placed screed leading to possible delays in the construction schedule.
For liquid screed the adhesive must be compatible with Anhydrite screeds (and not cement based),we recommend Tilemaster Adhesives.
We would be happy to discuss your requirements or answer any questions you may have.
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