Understanding Screeds – Which to use?

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When it comes to choosing a screed for your build, there are many options available; mainly

1. Traditional sand and cement screeds
2. Anhydrite screeds
3. Alphahemihydrate screeds – Easy Screed

Please refer to our comparative tables below, and see for yourself why Easy Screed is the best option on the market:

Sand & Cement Screeds

These are generally referred to as “semi-dry” screeds, a mix of Portland cement and fine aggregate. Installation of such screeds is slow and laborious and the final results are subject to good workmanship on site in the mixing and finishing process. With underfloor heating, traditional screeds are generally placed at 75mm + to try prevent problems with cracking. Problems often encountered with traditional screed include unlevel surface finishes, honeycombing and voids. They are also slow to dry before a finished floor can be installed. They may need to be left for up-to 60 days before the heat is turned on.

When used with underfloor heating, 75mm of screed turns the underfloor heating system into a slow response storage heating system. It is also quite common that additional floor levelling and preparation work will be required over the sand and cement screeds. This is often a hidden extra cost for customers.

		Traditional Screed Sand & Cement
Depth	10mm – 50mm 35mm minimum with underfloor heating	75mm minimum as per British Standards
Placement	Flowing liquid, placed by pump	Semi-Dry, finished by hand
Additional reinforcement	Not necessary	Requires steel mesh or fibres to attempt to prevent cracking
Materials	100% recycled alpha-hemihydrate binder, high-grade sand and water.	Sand and cement Plus additives to prevent cracking
Cracking/Shrinkage	None	Highly likely, Particularly with underfloor heating installations
Surface finish	Consistently flat, smooth level finish	Dependent on the quality of the flooring contractor
Quality Control	Produced in accordance with BS EN 13454, Parts 1 & 2 Tested CE Mark Certified Materials	n/a
Additional levelling required after placement	Not unless high-spec floor finishes requiring SR1 finish are being installed	Levelling compounds generally required before standard floor finishes, such as tiles, can be installed
Daily Output	800m² average daily output	100m² average daily output
Underfloor heating/ Drying	Can be turned on 5 days after installation of screed	Cannot be turned on until 28 days + after the screed has been placed
Underfloor heating performance	Thin screed – quick response time and easier to control	Storage heating – slow to heat-up and difficult to control when temperature changes
Drying	1 day per millimetre thickness poured in natural drying conditions. This can be sped up by turning on underfloor heating without any adverse effects	1 month per 25mm poured

Liquid Screeds
A new way of screeding has emerged in the Irish market over the past 6 years. With clear benefits over traditional sand and cement screeds, from the installation process right down to the finish, liquid screeds are becoming the new best practice for screeding. There are however, many types of liquid screeds:

1. Flowing cementitous screeds
2. Synthetic Anhydrites
3. Alphahemihydrates

Flowing Cementitous Screeds

An alternative to semi-dry screed, are flowing cementitious screeds, whereby the material is pumped into place. Such screeds have proven problematic, with problems of lifting, curling and cracking. They require chemical enhancements to assist with the fluidity of the materials.

Alpha-hemihydrates Vs. Synthetic Anhydrite Screeds
Easy Screed is an Alphahemihydrate, a natural binder material which holds many advantages over all other anhydrites;

The alphahemihydrate binder is subject to a sophisticated and highly controlled factory production process, which produces a more reactive and technically superior product than synthetic anhydrite screed, with a consistently high quality screed being achieved.

The production of the alpha-hemihydrate compounds requires more time, more care in selecting and preparing raw materials, and greater controls are necessary during blending. When water is added to an alphahemihydrate screed prior to application, it mixes better and more quickly, reacts faster and more completely, is easier to apply, dries faster and forms a flatter surface which requires minimal preparation for final floor coverings, without the need for grinding, which is always necessary with synthetic anhydrite screeds.

Synthetic Anhydrites generally involve the addition of chemical additives to the binder material. This will result in a skin or laitance layer forming on the screed the day after the pour. This prevents the floors being trafficked for several days after the pour. The surface layer must be removed, by sanding, at a later stage.
With synthetic anhydrites, if wetted again after the initial hardening, the chemical reaction will reoccur in the floor and it will re-soften.

	Easy Screed Alphahemihydrate	Synthetic Anhydrites
Catalyst to set floor	Water	Chemical Liquefier
Surface Finish	Smooth and flat With no skin left on top	Chemical starter leaves surface skin/scum on the floor surface, which requires removal
Setting	Can be lightly foot trafficked within 8 hours of being poured and work can continue on-site the next day	Surface skin delays drying out and hardening process – 1-2 days before foot traffic allowed, slowing the building process
Installation of floor finishes	Minimal preparation required before installation of final floor coverings	Require extensive grinding of the floor to remove the surface skin
Minimum Depth of Screed a) With underfloor heating	35mm including the diameter of the underfloor heating pipe	45mm – requirement for 30mm over top of underfloor heating pipe
Response to wetting eg flooding after floor has cured	No reaction – when reactivated with water no further reactions will happen – Floors remain hard and solid	Reactivate and soften, if in contact with water after initial installation

Remember,when comparing screeds, because they physically look the same does not mean they are the same. Ensure you are getting the highest quality products for your money by using Easy Screed.