A Commitment to Trusted Quality Tiling Support

The expertise behind the trusted BAL range of tiling adhesives and grouts is also always on hand to offer technical advice and support.

The BAL Technical Advisory and Specification Service handles approx 50,000 queries annually – providing FREE assistance, advice and specifications for all aspects of tiling installations.

In addition, a nationwide team of BAL Product Support Technicians are available to offer practical knowledge and on-site advice and training.

Some of the industry’s most frequently asked questions are highlighted below, along with their solutions – providing quick and easy guidance for the most common problems.

Contact the BAL Professional Enquiry Line on:

00353 863801042

Calls charged at local rate

For All General Enquiries call:

00353 1 8809210

Over 50,000 telephone enquiries per year

Free advice on all aspects of tiling

Free tiling specifications

Field investigation reports

Q: Should plaster walls be primed before tiling?


If using BAL cement-based powdered adhesives, apply 2 coats of neat BAL Prime APD or BAL Primer or 2 coats of BAL Bond SBR diluted 1:2 with water.

If using BAL ready-mixed adhesives, priming is not necessary UNLESS the plaster is very shiny and dusty. If so, brush surface with stiff bristle brush and prime with BAL Prime APD or BAL Primer diluted 1:1 with water or BAL Bond SBR diluted 1:4 with water.

Q: Why have cracks appeared in grout joints?

Possible reasons:

– Deflection in the substrate
– Moisture expansion in underlying boards that are not water resistant
– Tiles not adequately bonded to substrate
– Grout joints wider than max. recommended width for grout product concerned – resulting in drying shrinkage
– Joints not fully filled, leaving voids underneath grout – so grout not supported.

To increase flexural and (at tile edges) adhesion strength, and reduce water permeability, use BAL Admix GT1 or use a BAL epoxy resin-based grout.

Q: How to tile over heated screed?

See page 15 of the BAL Sitework Guidance literature for base preparation details.

Then fix tiles with 3-6mm bed of BAL Single Part Flexible or BAL Rapidset Flexible. When dry, grout with (min. 3mm joint) BAL Superflex Wide Joint Grout – or BAL Wide Joint Grout with addition of BAL Admix GT1 (diluted 1:2 with water) or BAL Microcolour Wide Joint Grout.

Q: How long should cement:sand screed be left before tiling?

3 weeks for Portland cement (including 7 days cure + 2 weeks continuous drying out in air) or 24 hours for screeds incorporating BAL Quickset Cement.

If not possible to allow Portland cement:sand screed to dry for 3 weeks, allow min. 24 hours for drying, then tile using BAL Green Screed Adhesive

Q: What is the best tile and grout for travertine tiles?

To avoid discolouration on travertine, limestone or other light-coloured stone, the adhesive should be a white cement-based adhesive.

Also, to avoid staining use a rapid setting adhesive. Ideal choices are BAL Rapidset Flexible Adhesive for walls and BAL PTB Flexible Adhesive (white) for floors.

Lay tiles with 3-6mm solid bed onto floors. Do NOT spot fix, as this may result in shading. To avoid migration of materials in solution into the travertine stone, use a grout colour similar to that of the tiles. To avoid ”picture-framing’ effect on very porous stone, seal tiles with a suitable sealer. Also reduce the risk by using cement-based grouts containing a water-retaining agent. BAL Superflex Grout, BAL Wide Joint Grout, and BAL Superflex Wide Joint Grout are all suitable for use with natural stone. Alternatively, use a rapid-setting grout such as BAL Microcolour Grout or BAL Microcolour Wide Joint Grout.

Q: Can 600x300mm porcelain tile be fixed to plasterboard wall with ready-mixed adhesive?

Not advisable.

Porcelain tiles have extremely low porosity. Ready-mixed adhesives rely on water loss through the joints, background substrate or tile to achieve full bonding. As the tiles have low porosity and joints are reduced due to the large tile size, ready mix products struggle to set. Instead, prime the plasterboard with neat BAL Prime APD or BAL Primer, and then use highly polymer-modified adhesive such as BAL Single Part Flexible or BAL Rapidset Flexible. These set via a chemical reaction.

Q: Are there weight restrictions when tiling onto plaster?


The maximum weight of tiling per m2 on Gypsum Plaster is 20kg/m2 or 32kg/m2 on Gypsum Plasterboard direct (i.e. without plaster skim) [See page 6 of the BAL Sitework Guidance literature]. As a general rule, remember to allow approx. 2-4kg/m2 for weight of adhesive and grouts in addition to the weight of tiles.

Q: How to fix ceramic tiles to calcium sulphate / anhydrite-based screed?

See page 12 of the BAL Sitework Guidance literature for base preparation details.

Protect floor against water ingress (moisture content must be <0.5% by weight or 75% relative humidity before tiling may begin. Measure moisture by hair hygrometer 75% RH or CM tester (‘speedy moisture tester’) or oven drying @ 40°C. Prime with 2 coats neat BAL Prime APD or BAL Primer and allow to dry. Then fix tiles with BAL Single Part Flexible or BAL Rapidset Flexible or, if incorporating underfloor heating; BAL PTB Flexible.

Q: Can timber floors be tiled?


Provided that they are capable of carrying the additional load, and are sufficiently stiff. To provide extra rigidity, noggings should be fitted between joists, as recommended in BS 5385-3. Alternatively, fix exterior grade or marine grade plywood (min. 15mm thick) over existing boards. Check that there is adequate ventilation and a damp-proof course. [See page 13 of the BAL Sitework Guidance literature for base preparation details of timber floors – including those with and without an overlay]. If direct fixing is possible, remove all traces of previous finishes (stain, varnish) before tiling. Lay a solid bed of BAL Fastflex Adhesive, ideally 3-4mm thick. If fixing to an overlaid timber floor, lay a solid bed of BAL Single Part Flexible Adhesive or BAL Rapidset Flexible Adhesive, ensuring NO voids left underneath tiles.

Q: What's needed when tiling a wet room?

Above all, make sure the walls/floor are suitable for regular wetting.

They should be waterproofed/tanked with BAL WP1 Coating, reinforced with BAL WP1 Polyester Tape/Membrane [See page 17 of the BAL Sitework Guidance literature]. Use adhesives suitable for the tile type and substrate. All BAL dispersion (ready-mixed) and cement-based adhesives are compatible with BAL WP1 Coating. If a power shower is being installed, check that the chosen adhesive is suitable. Grout: If single-head showers (including power showers), BAL Superflex Grout, BAL Microflex Grout, BAL Superflex Wide Joint Grout and BAL Microflex Wide Joint Grout are suitable. If multi-head shower and body jets, consider using BAL Easypoxy Grout