How to tile onto anhydrite using the BAL Flexbone 2Easy

Calcium Sulphate is the name of the binder that is used in the screed. Traditionally, screeds are cement-based however this type is an exception and uses calcium sulphate rather than cement. It’s a by-product of the chemical industry in the UK that gets milled for reuse rather than landfilled.

These types of screeds contain anhydrous (dry) Calcium Sulphate and aggregates instead of a cement-based binder. The binder comes as either an alpha hemi-hydrate (a stronger and harder crystalline form) or anhydrous Calcium Sulphate. When water is added, the binders will form calcium Sulphate dihydrate – more commonly known as Gypsum. This reaction stops when the vast majority of the Calcium Sulphate binder is used up and is generally complete after a period of 3-7 days, leaving the remaining water to evaporate through the surface of the screed.

Simply sweep the solid level floor and lay BAL Flexbone 2Easy. This is a unique floating loose lay uncoupling mat requiring simple preparation, there is no primer or adhesive needed. You can tile immediately on to the anhydrite floor without the need to remove the laitance layer. You can also fast track tiling on new anhydrite screeds that aren’t yet cured, up to a maximum of 1.5% CM residual moisture (Calcium Carbide Method). The moisture evaporates through the covering joints of the Flexbone 2Easy.

Ceramic tiles should be a minimum of: 200mm x 200mm x 10mm

Porcelain tiles should be a minimum of: 200mm x 200mm x 8mm

Natural Stone should be a minimum of: 200mm x 200mm x 15mm

Roll out the BAL Flexbone 2Easy with the blue mesh side up. Roll out from the corner and cut precisely to the required length and sizes as required for the floor. Trim off any excess around up-stands using scissors or a utility knife.

Note: leave a 6mm movement joint around the perimeter.

Butt joint the edges of the BAL Flexbone 2Easy, the overlapping blue mesh covers the joints between the roll lengths. BAL Flexbone 2Easy is to be laid with all necessary expansion joints in place.

To ensure freedom of movement of the subsequent covering structure, tape all movement joints using a suitable proprietary self-adhesive tape. This will protect against the entry of the wet adhesive bedding material through the joints onto the existing floor during installation. Apply the BAL Flexbone Joint Tape to all Flexbone 2Easy roll end joints to ensure the mat moves as one.

You cannot use BAL Flexbone 2Easy in wet areas.

Please watch the video at the start of this article for a visual guide on laying the BAL Flexbone 2Easy.

Make sure you plan ahead so you are able to exit the room without stepping on any tiles as they won’t have set. If the room is essential, you can tile half of the room at a time, so you are still able to access the room.

Always ensure the correct adhesives and grouts are selected for the installation and mix the recommended tile adhesive in a mixing bucket as per the instructions on the bag.

We recommend you use BAL Rapid Flex Fibre or BAL PTB Fibre Plus. To apply tiles, mix and apply a BAL flexible adhesive to the mat using a thick bed solid bed trowel. If using a large format trowel, ensure the final bed thickness of the tile adhesive does not exceed 5mm over the BAL Flexbone 2Easy. This can be avoided by using a trowel no bigger than 12mm.

Alternatively, if you don’t wish to use the BAL Flexbone 2Easy, you can see our guide on the more common method here.