FAQs

Surface Prep Products

1. How clean does the subfloor have to be before I apply any adhesive?

Floors should have no oils, grease, dirt or any type of contaminants. For further questions, please contact your local Technical Representative for specific product recommendation.

2. What existing floor coverings can smoothing compounds be poured over?

Smoothing compounds can be poured onto tiles as long as they are clean, well bonded and free of all contaminants. Smoothing compounds should not be poured over coverings like carpet or vinyl. For further questions, please contact your local Technical Representative for specific product recommendation.

3. Do I need to apply primer before installing the smoothing compound?  Should the primer be diluted or used at full concentration?

Yes, primer is necessary to prevent future failures and to achieve the best performance from your smoothing compound. Whether it should be diluted or not will depend on what outcome you are trying to achieve.

For further questions, please contact your local Technical Representative for specific product recommendation.

4. Do I have to prime between smoothing compound applications?

Yes, you must apply a coat of primer between smoothing compound applications. For further questions, please contact your local Technical Representative for specific product recommendation.

5. Can I mix the product to feel?

No, each product is designed based on product performances. Please refer to the specific product TDS for water demand and mixing instructions. For further questions, please contact your local Technical

Representative for specific product recommendation.

6. How long should I mix?

Always mix the material until it is free of lumps and has reached a homogenous mix. Typically, this should take around 2 minutes. Please refer to the specific product TDS for mixing instructions. For further

questions, please contact your local Technical Representative for specific product recommendation.

7. Can I add more water if it feels thick or I need to increase the flow?

No, each product is designed based on product performances. Please refer to the specific product TDS for water demand and mixing instructions. For further questions, please contact your local Technical

Representative for specific product recommendation.

8. Can I mix a partial bag?

No. It is crucial the correct amount of water is used in order to obtain the ideal performance of each product.

Hardwood Adhesives

Q1. Do I need to get the entire old adhesive off the floor before I start applying the new adhesive?

Yes, slab must be contaminants free and well prepared before you can proceed with the Adhesive Installation. For further questions, please contact your local Technical Representative for specific product recommendation.

Q2. Do you sell it in a smaller quantity?

Yes, Bostik offers some available in cartridges as well as in gallon buckets

Q3.   How much adhesive do I need for my job, square foot coverage?

Based on flooring type and installation type, always refer to the product TDS. For further questions, please contact your local Technical Representative for specific product recommendation.

Q4.   What is the difference between all the Bostik hardwood adhesives?

Varying moisture vapor protections, sound reduction, easy to trowel, no VOC, easy cleanup plus difference in polymer chemistries.For further questions, please contact your local Technical Representative for specific product recommendation.

Q5.   Can I install over old glue-floor adhesive?

No, slab must be free of contaminants. For further questions, please contact your local Technical Representative for specific product recommendation.

Q6.   Will these adhesives bond to various coatings on my concrete? (moisture barriers, sealers, cutback, etc)

Approved substrates are located on the technical data sheet. For further questions, please contact your local Technical Representative for specific product recommendation.

Q7.   What size trowel do I use?

Recommended trowel sizes are located on the technical data sheet (TDS)specified upon type of wood and application. For further questions, please contact your local Technical Representative for specific product recommendation.

1. Can I use a hardwood-flooring adhesive to adhere a vinyl floor covering?

No, we have a vast range of adhesives that are suitable for vinyl. For further questions, please contact your local Technical Representative for specific product recommendation.

2. Does the Soft Flooring Adhesive provide a moisture vapor barrier?

No, Bostik has specific products developed for moisture and vapor barriers. For further questions, please contact your local Technical Representative for specific product recommendation.

3. Is this a wet lay installation or is there a waiting time?

Waiting times will vary between products. For further questions, please contact your local Technical Representative for specific product recommendation.

4. What type of substrate preparation is needed prior to applying the adhesive?

Follow the current standards for floor preparation; subfloors should be free of dust and paint, markings oil, curing or release agents, sealers or existing adhesives. Absorbent subfloors may be necessary for some adhesives. For further questions, please contact your local Technical Representative for specific product recommendation.

5. What trowel size is needed?

Trowel sizes and coverages are located in the TDS. For further questions, please contact your local Technical Representative for specific product recommendation.

6. What is the working time of these adhesives? 

The dry lay method is the most common installation method used for a PSA adhesive. Once the adhesive is dry to the touch the working time is the amount of time the installer has to lay the flooring into the

adhesive before it becomes less effective in bonding and tackiness. For further questions, please contact your local Technical Representative for specific product recommendation.

How long should sand and cement screeds be left before tiling?

Screeds should be left to dry for at least 3 weeks prior to tiling. BS 8204 recommends 1 day per mm for thicknesses up to 50mm. Normally 3 weeks is the absolute minimum.
This would equate to:
Screed thickness : 50mm 

Estimated drying time : 4-6 weeks

Is there any way to speed up the screed drying time before tiling?

Screeds should be cured for at least 7 days by covering with polythene or an impermeable membrane. They should be subject to continuous air drying after curing for at least 2 weeks before tiles are applied. 
If tiling with porcelain tiles, you should adhere to the full drying time for the thickness of the screed. For additional advice please contact your local Technical Representative.

How do I prepare timber floors for tiling?

Wooden floors have natural movement through bend and bounce and can expand. Tiles can crack under the pressure if installed incorrectly. To increase the floor’s rigidity and strength, you should overlay it with tile backer boards or 18mm exterior grade plywood.

How do I tile over a floor with underfloor heating?

Once the screed has fully dried, the floor should be gradually heated by no more than 5°C per 24 hours, up to 25°C. This should be maintained for a couple of days, then allow the floor to cool to room temperature. Before any tiling work is carried out, ensure the heating has been turned off for at least 48 hours. It must not be turned on again until at least 7 days after the work has been completed. Again, the temperature should be increased by no more than 5°C per 24 hours, up to 25°C. This is necessary to prevent delamination and cracking caused by thermal shock. 

Can I put Quartz (resin agglomerated) tiles onto heated floors?

Yes, but the maximum continuous area for tiling a heated floor with Quartz should be 25m2.

Which tiling adhesive should I use for Quartz tiles?

An S2 tiling adhesive should be used when applying Quartz to allow for the greater movement that this type of tile experiences. Fix onto a correctly prepared base with Bostik MC400 Supa-Flex adhesive or MC250 Vitri-Flex adhesive. Incorporate Bostik AP 250 Flexibond at a dilution rate of 1:1 parts clean water.

What size of tile is considered a large format tile?

Large format tiles are tiles with a surface area greater than 3,600cm² and with a tile edge up to 120cm.

What size of tile is considered a panel tile?

Panel tiles are tiles with a surface area greater than 10,000cm² and with any tile edge over 120 cm.

How should I install large format or panel tiles?

Your surface should be flat and stable and you will need to consider movement joints at the design stage. A perimeter movement joint needs to be installed, and in large areas movement joints need to be installed at 3m to 4.5m centres.  You should also install movement joints at thresholds where the tile bed abuts other constructions.

Many large format tiles and panels require at least 2 people to handle and fit them. Specialist tiling tools are required to handle and fix thin, large-format porcelain tile panels.

Solid bed fixing (including back combing of the tile) is required when fixing large format tiles and panels. Large format tiles should be installed using a Bostik powder adhesive, such as MC 310 OPF.

A minimum of a 3mm grout joint is required for large format tiles. A 5mm grout joint is required for single panels of 3m or more in length. We recommend Bostik J115 Smooth Grout for grouting tiles or panels. Bostik S115 Silicone should be used to fill movement joints and where the tiles or panels abut another surface.

If the joints are less than 6mm wide, there should be a deviation of no more than 1mm.

Can I use a ready-mix floor tile adhesive to stick down any type of tile?

A suitable ready-mix adhesive, such as Bostik EVO-STIK Floor Tile Adhesive for Wooden Floors, can be used to fix ceramic tiles. For any other tile types, we recommend a Bostik cementitious powder adhesive.

What is the maximum tile size that can be installed with a ready-mix wall tile adhesive?

Most tiles up to 30cm x 30cm can be fixed to plaster, plasterboard or tile backer boards using a ready-mixed adhesive. However, always consult the packaging and/or the product’s Technical Data Sheet.

What are the heaviest tiles that can be installed on a wall?

Gypsum plaster including skimmed plasterboard, can carry a maximum tile weight of 20kg/m2. This equates to ceramic tiles about 8mm thick or natural stone tiles of about 7mm thick, both with an adhesive bed thickness of 3mm maximum. 

Paper-faced plasterboard can carry a maximum tile weight of 32kg/m2. This equates to ceramic tiles of about 12.5mm thickness and natural stone tiles of about 10mm thickness, both with an adhesive bed thickness of 3mm maximum.

Tile backer boards can hold 50–60kg/m2. This would equate to tiles that are 20mm thick.

Do I need to fully tank a wet room? 

Fully tanked is where the walls and floors are all made watertight. This is not required for a wet room. Only ‘wet zones’ – areas that will have intense water forced upon them frequently –need to be made watertight. 

Can I tile over existing tiles? 

Yes. Remove any loose or hollow-sounding tiles and make good the area with Bostik Rapid Repair Mortar. The surface must be perfectly dry and particular attention should be paid to cleaning - ensure grease, grime and any parting agents are removed.
Tile-on-tile applications can present problems with regard to weight if on plaster or plasterboard backgrounds. 20kg/m2 and 32kg/m2 are the maximum weights recommended to be applied to plaster and plasterboard respectively.

Which tiling adhesive should be used with porcelain tiles?

Solid porcelain tiles are non-porous products, so a powdered tile adhesive, such as Bostik MC310 OPF adhesive or Bostik MC250 Vitri-Flex, is recommended.

Which is the best waterproof adhesive for showers?

For areas that are not frequently wet, a ready-mix adhesive such as Bostik A100 Showerproof can be used. For areas of frequent wetting a powdered adhesive, such as Bostik MC310 OPF, is recommended.

How long does it take for tiling grout to dry?

For general applications 24 hours is required, but for wet room applications the grout should be allowed to dry for 2 weeks to ensure it is dry throughout and not just on the surface.

How do I use silicone in place of grout?

For a successful silicone installation, always ensure the area is clean, free from contaminants and dry before the application starts. 

Gun the silicone in the location required and smooth into position with a plastic shaping tool to avoid any secondary contamination.

Skinning will take place within the first 24 hours and full cure can take approx. 48 hours. The silicone should be cleaned regularly to avoid the development of mould.

Which adhesives and grouts can I use for tiling swimming pools?

We generally recommend Bostik MC310 OPF adhesive and Bostik J115 Grout. However, there are many considerations when creating a swimming pool, so we advise that you consult The Swimming Pool and

Associated Trades Association (SPATA) for technical guidance.

Do I need to use primer before tiling? 

We recommend always priming a substrate to ensure the best tiling results. Bostik’s SBR is as an excellent all-round primer and bonding agent that is especially suitable for external applications. 

Where surfaces are prone to very minor movement and vibration, or where direct fixing to glazed tiles or other impermeable surfaces is required, we recommend Bostik AP 250 Flexibond.