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Your Liquid Screed Questions Answered
What is a flowing screed?
Screedflo flowing anhydrite liquid screed is a cement-free screed made from selected sharp sand, an anhydrite (calcium sulphate) binder, and water. It is supplied in liquid form, allowing it to flow easily and create a smooth, level floor surface suitable for residential and commercial applications.
How does Screedflo compare to traditional sand and cement floor screeds?
Anhydrite screed is calcium sulphate based. As it is a liquid, the finish is much smoother, flatter and the screed is faster to install. It is a stronger product than traditional sand and cement screed, and so can be laid thinner. It conducts the heat from UFH pipes up to 5 times more effectively.
What can liquid screed be used for?
Flowing screed can be used for almost any internal application to provide a level, flat, smooth surface to an SR2 finish, for all types of floor coverings, either domestic or commercial. Please see the Our Products page on our website.
Can flowing screeds be used with under floor heating?
Anhydrite screeds are ideal for application over both electric and water under floor heating systems because of the flowable consistency that fully encompasses the heating pipes. Flowing screeds have excellent thermal conductivity and minimal thermal expansion. Projects with underfloor heating will benefit from significant savings in energy costs by using anhydrite screed.
What about cracking? Do flowing screeds need reinforcement to prevent cracking?
Flowing screeds are much stronger than traditional screeds and do not require reinforcement as they do not curl and shrinkage is extremely low, minimising the risk of cracking. Joints are required less frequently than with traditional screeds, but recommended through doorways and between areas of heated and non heated screeds. Check out our preparation advice.
How much do I need?
Use our online screed calculator to calculate the volume of liquid screed required by entering your room dimensions.
When can I walk on the screed?
Leave to dry for 48 hours, and then open the windows or building to allow ventilation. Light foot traffic after 48 hours. Protect from rain or the ingress of water. Protect from direct sunlight. Then after 7 days you can work on the screed as normal, and put up any non-load bearing partitions etc.
Does Screedflo deliver to my area?
We operate in East Anglia, the South East and the Home Counties. For larger jobs outside these areas please telephone us as we may still be able to deliver to you.
Will the Screedflo vehicle be able to access my site?
Our vehicles can access most sites that a concrete lorry can access, but must always be on a hard standing area. We can pump the material 100-150 metres from wherever the Screeedflo vehicle is parked. We will make a site visit before the installation date to check access, water supply and that the preparation of the floor is suitable for liquid screed.
What do I need to do before delivery?
You will need:
Safe hard standing for the Screedflo vehicle
A mains pressure water supply (we supply hoses)
A wash-out area or lined skip
These details are checked during the site visit.
You will also need to prepare your area for screed installation. See our preparation guidance for more information.
What happens once the delivery arrives?
On arrival, our team will:
- Confirm datum and critical floor levels using a laser
- Set up tripods and pumping equipment
- Begin batching the selected Screedflo product on site
Pumping typically takes around 8 minutes per m³. Once complete, the system is washed out and the delivery note signed.
Can a stiff brush be used instead of sanding to remove laitance?
A stiff brush can remove loose laitance, but mechanical sanding is still required to provide a proper key for primers and adhesives. A light industrial sander (e.g. STR701) should be used to remove stubborn debris such as plaster or mortar.
Will commissioning UFH after 7 days cause cracking?
No. Anhydrite screeds are strong and flexible. If the underfloor heating is commissioned gradually in line with guidance, there is little risk of cracking or thermal shock.
Will UFH clips puncture the membrane?
No. Liquid screed will not seep through UFH clip holes. Any splits in the membrane should be sealed with waterproof gaffa tape before installation.
Can I install a 75 mm screed to prevent cracking?
A 75 mm screed is not required. Anhydrite screeds are designed to be laid at 40 mm on insulation or 50 mm with UFH. Thicker screeds take longer to dry and often perform worse than increasing insulation thickness.
Why do I need an edge strip if I don’t have UFH?
All screeds expand slightly as they dry. Edge expansion strips allow controlled movement and help prevent cracking, even without underfloor heating.
Can reinforcement mesh be used?
No. Screedflo liquid screed does not require reinforcement. Mesh provides no benefit and can make installation more difficult.
Why does anhydrite screed need sanding and priming?
All screeds require sanding to clean the surface and provide a key. With anhydrite screeds, a compatible primer is essential to prevent chemical reactions with cement-based products.
Do anhydrite screeds take longer to dry?
No.
Screedflo Rapide: around 14 days at 50 mm
Screedflo Standard: around 28 days at 50 mm
Sand and cement screeds are laid thicker and generally take longer to dry. Anhydrite screeds can also be force-dried using UFH after 7 days. All screeds require sanding to clean the surface and provide a key. With anhydrite screeds, a compatible primer is essential to prevent chemical reactions with cement-based products.
Can anhydrite screed be used in garages?
Yes. We recommend Screedflo Extra Strength. Once dry, it can be protected with an industrial resin coating and provides superior strength compared to traditional screeds.