QUESTIONS YOU WOULD LIKE ANSWERING ABOUT ANHYDRITE SCREED

What is anhydrite screed?
Where is anhydrite screed appropriate to use?
What are the benefits of using an anhydrite screed?
Is there anywhere where anhydride screed should not be used?
Can I tile onto anhydrite screed?
Is there any product I can use to prevent the lifting of tiles on a anhydrite floor?

What is anhydrite screed?
An anhydrite screed is a screed which is applied through a pump.  It is a self leveling screed based on a calcium sulfate binder.

Where is anhydrite screed appropriate to use?
It is used primarily in new-builds either within domestic or commercial projects but it is suitable for most applications from heavy duty to light duty areas.

What are the benefits of using an anhydrite screed?

• This product is a relatively inexpensive, easy to lay, fast setting, pumpable, self-leveling screed.
• Flowing screeds are applied in liquid form through large hoses.  This method produces a quicker, smoother finish. A skilled team and the right equipment can potentially receive an output of 1000sqm or over in a day.
• The thickness can be laid thinner than sand/cement screed.  Generally the screeds overall thickness is around 55mm compared to 75mm for the sand/cement screed, although it is possible to lay this screed thinner in selected areas.
• Provides an efficient flow around pipes by forming intimate contact that is not possible to achieve with the conventional method using sand/cement screed.
• The intimate contact along with the thinner screed improves energy efficiency for the underfloor heating systems. It is essential however, that the heating system is compatible with the anhydrite screed.
• This product does not curl and is less susceptible to shrinkage or cracking. This makes this method particularly efficient when laying a floor for example in large arenas or sports halls.
• When it is first laid it is possible to take light foot traffic within 24 - 48 hour (weather conditions dependant) of installation, making areas available sooner to the following trades; which is usually after 5 days.  However, if thickness exceeds 40mm allow 1mm per day.
• There is hardly any construction required of the joints.
• This product is free from protein and therefore will discourage the growth of bacteria.

Is there anywhere where anhydride screed should not be used?
Yes, these screeds should not be used externally or in damp or wet conditions.

Can I tile onto anhydrite screed?
Anhydrite screeds can be a problem to tile onto because when a cement based adhesive is applied directly onto this type of flooring, it reacts with the gypsum (which is the product that allows the screed to flow).  This in turn causes a reaction with the associated structure and the tile will debond away from the tiles causing them to lift.

Is there products available which can prevent the lifting of tiles on a anhydrite floor?
Yes, you will need to apply an anhydrite primer to the floor but firstly you must check that the humidity is less 0.5%. This can be tested with the use of a humidity tester. If the humidity reads under 0.5% the next step is to thoroughly clean off any surface residue from the screed. Apply one coat of the anhydrite primer, leave to completely dry before applying a second coat of the primer.  When both coats have been applied leave for at least 4 hours, (this is dependant on the weather conditions) before beginning to fix the tiles. Once the primer is set you can now tile using a flexible adhesive such as Benfer C2. The above procedure can also be followed when electrical and hot water underfloor heating is present.

If you have any further questions on any of the above products you can email us at www.enquirestilersmerchants.co.uk 

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