Liquid Screeds are a relatively new solution to the Australian Market they are very common place in Europe with approx 40% of screeded floors in the UK using Liquid screeds and around 70% in Germany.
Liquid screeds have been in use in the UK for over 20 years and in Germany for almost 80 years, but it is relatively new in the Australian market,
Liquid floor screed market share in Europe has become more popular in recent years
Calcium sulphate liquid floor screed (with a calcium sulphate binder) is our preferred liquid screed. There is available (coming soon) a liquid floor screed that is cementitious. However we currently have the calcium sulphate screed because that is by far the biggest-selling and most versatile and reliable liquid floor screed on the market.
The product is pump applied only (small bagged volumes can be mixed on site), it is the only way for large volumes of the product for it to be supplied. It is supplied via a concrete truck mixer (aggie truck), fed into a screed pump and then pumped directly to the area where it is needed.
Floor levelling screeds are normally used where there is a structural substrate, the screed itself isn’t normally structural. It can be used in the following applications:
Calcium sulphate liquid floor screed has very low shrinkage, when compared with traditional sand and cement. This means there is a minimal risk of cracking and no curling that you can sometimes see with cementitious products.
With low shrinkage comes less joints. Assuming the aspect ratio is 2:1 or less with no restraints in the screed, re-entrant corners, columns, then the maximum area without joints would be 1000m2. For liquid floor screed with underfloor heating assuming the same things would be 300m2. With a greater aspect ratio and/or restraints the maximum m2 would be reduced.
You may want to consider movement joints if you have a heated screed, and would want to separate different zonal areas. Placing a joint between zones will minimise egress of heat into the neighbouring zone. With thermal movement, having two areas heated at different temperatures, with no joints could cause thermal movement cracking.
The weakest area within a screed would be the shortest span, this is likely to be across doorways, and would be an obvious place to form a joint.
Liquid floor screed can generally be trafficked after 24 -48 hours.
The screed is pumped into place and this enables high productivity, laying up to 2,000M2 a day. Productivity is dependent on the following:
It is possible to 2,000m2 in a day
When compared to traditional sand and cement, the thickness of liquid floor screed can be reduced. A thinner screed will generally give you a fast drying screed.
It can be force dried after seven days, by turning the underfloor heating on, and/or using dehumidifiers (cementitious screeds, would not be forced dried). After seven days, the crystallisation of the binder has taken place, and the moisture is not needed and can just be extracted.
Any commissioning of the heating the screed needs to be controlled under strict guidelines.
The screed must be dry before the floor coverings can be applied, and a moisture test is essential.
If it is laid on a damp substrate, then it is likely to delamination. There are lots of factors that can enhance or prevent the drying process.
Because of the density of the product, the efficiency and thermal conductivity is greater than a sand and cement screed. Calcium sulphate liquid floor screed is quicker to respond, quicker to heat, quicker to also cool down. this makes hydronic heating and cooling systems very efficient and effective
Calcium sulphate liquid floor screed is self-compacting. With a traditional sand and cement, you need to compact the product to make sure that you get full strength, with this product, it is self-compacting.
It is not suitable for permanently wet areas such as changing rooms, where a cementitious product would be more suitable.
A 6m3 delivery would take approximately 30 minutes to discharge, from truck mixer to project.
Once the screed is in position, it would then be finished with what is called a “dapple bar”, a rounded aluminium bar, to first of all remove the air bubbles, on the first pass. Then at 90 degrees to the first pass, you would then pass again, and this time the bar would just bounce on the surface of the screed, and this would produce a smooth levelled surface that is then suitable for your floor coverings.
When applying floor coverings, calcium sulphate liquid screed and cementitious adhesive directly are not compatible. A primer would be required when using any cementitious products. You can also purchase adhesives that are calcium sulphate, and would be compatible.
If you have any further questions regarding what is liquid floor screed, please contact us. We would love to help!
