Brit Adhesives FAQ
Brit Adhesives answers some of your most frequently asked questions...
Q1: What is the difference between S1 and S2 tile adhesive?
A: Cementitious (powder based) tile adhesives classified as S1 or S2, are determined by their flexural strength. Generally an S1 classified adhesive such as BritFlex S1 Rapidset
or BritFlex S1 Slowset will be suitable for most applications. However, in areas subject to lots of vibration or movement, it is recommended to use an S2 classified adhesive for
extra confidence.
Q2: Can I use ready mixed adhesives to fix large format tiles and floor tiles?
A: No. Ready mixed adhesives are only suitable for the installation of mosaic tiles, ceramic tiles up to 300x300mm and porcelain tiles up to 150x150mm. Larger format tiles
and any tiling application associated with a floor should be tiled using a cementitious (powder based) tile adhesive.
Q3: Can I prime the surface using PVA?
A: No. Any surface that requires priming should be primed using the appropriate priming agent (i.e - BritPrimer, Britprimer HD, Brit-Prim Grip). PVA when applied to the surface forms a dry film which has a tendency to re-soften when it comes back into contact with moisture. Because water is used to mix cementitious tile adhesives, this exposes the layer of PVA to moisture and as the cement based tile adhesive cures by hydration it begins to harden which in turn puts stress on the interface with the primer. The crystallisation curing process taking place on a now weakened PVA background has high potential for reducing the overall bond strength between the adhesive and the substrate. The end result is likely to be adhesion failure resulting in tiles completely de-bonding from the surface.
Q4: Do I have to prime the substrate?
A: Yes, priming the substrate before tiling is a necessity that ensures the selected smoothing underlayment can perform to its optimum performance. Priming before tiling offers three advantages 1) it reduces the absorbency of the substrate 2) it increases adhesion for better bond strength 3) correct priming acts as an interface between materials
preventing failure by reaction (i.e – priming calcium sulphate screeds prior to laying tiles ensures there is no chemical reaction between the screed and the adhesive which
can cause adhesion failure).
Q5: Why does my grout have white / light coloured patches?
A: White or light coloured patches is known as efflorescence; a common culprit that affects many cement based products (not just grouts) due to their water and lime soluble content. Efflorescence occurs during the drying phase with the soluble lime being deposited on the surface as a dry white or light coloured powder as the water evaporates. Efflorescence unfortunately cannot be completely avoided but steps can be taken as not to aggravate the issue 1) do not exceed the water requirements for mixing the grout
2) do not use excessive water when cleaning down grout joints 3) warm and dry conditions following installation will assist the drying process.
Q6: Can I use a levelling compound for exterior applications?
A: Levelling compounds are universally only used for internal applications and should never be used outside.
BritLevel Flexible, BritLevel Reinforced and BritLevel Gypsum are for all interior use only.
Q7: What adhesive should I use when installing backer boards?
A: When installing backer boards, Brit Adhesives recommend using an S1 classified adhesive (BritFlex S1 Rapidset or BritFlex S1 Slowset). If the backer board is going to be subject to lots of vibration or movement, then upgrading to an S2 classified adhesive is the recommended course of action (BritFlex S2 Rapidset).
Q8: How do I tile to existing tiles?
A: If levelling is not required and the existing tiles are in sound and good condition then the tiles can be primed using Brit-Prim Grip. Apply the first coat to the substrate using either a brush or roller and allow to dry (usually 1 hour based at 15°C and a relative humidity of 50%) before applying a second coat 90° to the first. Brit-Prim Grip creates a textured grip surface that increases bond performance as tiles may be installed as normal using any of the BritFlex range of cementitious (powder based) adhesives.
Q9: Why do certain substrates require long waiting times before tiling?
A: Substrates that require longer waiting times before tiling can begin is due to the substrate gradually shrinking over the course of its drying period. Any attempt at tiling during this drying process will more than likely result in tiles de-bonding from the substrate, costing time and resources. Waiting for the substrate to fully dry and then tiling greatly reduces the risk of installation failures. Below is the recommended waiting times before tiling:
Concrete – 6 weeks
Sand and Cement Screeds – 3 weeks
Sand and Cement Renders – 2 weeks
Plaster – 4 weeks
Q10: How do I waterproof bathrooms, showers and wet areas before tiling?
A: Areas that require waterproofing before tiling should be tanked using the Brit Adhesives Aqua Showerproof Kit that comes complete with 5kg Brit AquaSeal, 1ltr Aqua Primer and 10m Aqua Waterproof Tape. Surfaces should first be primed with the Aqua Primer and then tanked with Brit AquaSeal using either a roller or brush, applied at a thickness of at least 1mm. The Aqua Waterproofing Tape should then be applied to any joints using a thin layer of Brit AquaSeal (at least 1mm thick) to ensure the waterproof barrier is continuous. Wait for the first coat of Brit AquaSeal to dry (usually 1-2 hours) before applying a second coat 90° to the first. Once the second coat of Brit AquaSeal has dried the area is now suitable for tiling.
Q11: Do weather conditions affect my adhesive and grout?
A: Yes, adverse weather conditions can affect tiling and grouting which may alter pot life and open time periods as well as the overall performance of the product.
During winter periods, cold conditions can greatly reduce the speed of reaction between the cement and water. This will result in prolonged setting times for the adhesive and grout and also reduce the initial hardening of the adhesive. Cementitious (powder based) adhesives and grouts should not be used below 5°C as the reaction between the cement and water all but stops. In freezing temperatures, water contained in the mix with the cement may freeze which can cause irreversible damage.
The summer period with hot and dry conditions greatly increases the reaction between the cement and water: Setting times of the adhesive will be significantly reduced as well as the initial hardening of the adhesive, resulting in much shorter pot life’s and open times. Cementitous (powder based) adhesives should not be used in temperatures above 30°C as the elevated temperature can make the setting time so quick it makes the adhesive unworkable.
Q12: What is a decoupling membrane and what does it do?
A: A decoupling membrane is a unique form of anti-crack matting that helps stabilise the floor substrate and the tiles. Decoupling membranes (also known as uncoupling membranes) does just what it name describes: it un-couples, or isolates, the substrate from the tile, allowing them to move independently of each other so that movement in the substrate doesn’t cause the ceramic, stone, or porcelain tile to crack. Decoupling membranes are extremely versatile as they can be used for both interior and exterior applications and can be installed on a multitude of different substrates.
