Specifying Resin-Based Grouts

The purpose of grout is to fill the joints that are left between tiles, make them watertight and protect the tiles themselves from water damage.  There are two basic types of grout to choose between when specifying tiling.  The first is cementitious grout which is a powdered mix of cement binder and aggregate to which water is added.  More advanced grouts have additional components including polymers to give them enhanced characteristics such as mould and bacteria resistance or faster setting times.  The second type are resin-based – this is normally epoxy resin mixed with a filler: the type of filler depends on the brand of grout.  However a new sort of water-based resin has recently been developed which has advantages over the traditional resin-based grouts.

Resin-based grouts tend to be more expensive than conventional cement based grouts.  They can also be more difficult to use.  However they set harder and do not break down as easily as the latter giving them advantages in certain situations such as areas where hygiene is very important or where the grout may be subjected to aggressive chemicals, such as swimming pools.

International Standards

The international standard for grouts for ceramic tiles and natural stone is ISO 13007-3 whilst its UK equivalent is BS EN 13888.  Both of them look at the same criteria to decide whether a grout is fit for purpose.  These are compressive & flexural strength, abrasion resistance and water absorption. 

Cementitious grouts are classified as CG1 or CG2 with CG2 grouts performing to a higher standard.  CG2A grouts have better abrasion resistance whilst CG2W absorb less water than standard grouts.  Reactive resin grouts are classified as RG.

ISO 13007-3 Standard Values

Value Test Standard Min Value at 28 days for Pass
Compressive strength ISO 13007 Part 4.1.4 – 5 ≥15 N/mm2
Flexural strength ISO 13007 Part 4.1.3 – 5 ≥2.5N/mm2
Abrasion resistance


ISO 13007 Part 4.4 ≤1000 mm3 (Class A high resistance)
Water absorption ISO 13007 Part 4.2 ≤5g after 30 mins & ≤10g after 240 mins. (≤2g after 30 mins & ≤5g after 240 mins = W rating for reduced water absorption).

 Other Values to Take into Consideration

Whilst not included in the standards there are other very important factors that should be taken into account when specifying grout.

Colour Fastness & Uniformity

Grout is now available in a myriad of colours which can either be matched to the tile causing the grout lines to recede or used in a contrasting colour for decorative effect. In both cases it is imperative that the colour is uniform and does not fade with time.

Most colour degradation is caused by three factors: light, temperature and humidity. Together, these factors can cause more damage than the sum of their individual parts. The grout therefore needs to be tested to stand up to all of three.

Resistance to microbial attack

Many micro-organisms do not grow in environments with a pH value greater than 9 and the pH value of cementitious binders is higher than this. However over time their pH value drops due to salification and this allows mould, fungi and bacteria to grow.

There are various ways to limit the growth of such micro-organisms, although some of them engender other problems. The use of chemical, anti-mycotic and bactericide substances in the formulation of products for the building industry can lead to a wide range of diseases and dysfunctions depending on the active principle used. That is to say that several of these substances, which to all intents and purposes are common pesticides, have been classified as potential carcinogens based on their inherent toxicity and tendency to migrate and enter the atmosphere. Whilst their use in farming is very strictly regulated, there is no similar regulatory system governing their use in indoors, although it is the major area of exposure for most people.

Resistance to Chemical Attack

Resistance to attack by household and industrial chemicals is another area that is not covered by the standards. Whilst most grouts are inert and will resist chemical attack when newly installed, over time the grout can break down and be affected.

When to use Resin-Based Grouts

The surface of epoxy grouts tends to be smoother and more resistant to attack by chemicals and the growth of mould and fungi than that of cementitious ones. They are therefore more suitable for use in areas where this needs to be taken into consideration, for example clinics, hospitals and other hygiene areas, food preparation areas, saunas, spas and industrial areas that could be exposed to harsh chemicals.

Another factor to be taken into account is the surface of the ceramic tile: soft glazes, often present on hand-made and hand-decorated tiles, can be scratched by cementitious grouts if they have coarse grains, whereas a resin-based grout will be less likely to scratch the surface.

Fugalite Range

Kerakoll’s Fugalite Bio is a range of water-based resin grouts, certified EMICODE EC1-R Plus with very low VOC emissions. This class of grout has various characteristics that make it superior to reaction resin grouts formulated in the traditional manner.

UV Resistance

Colour durability tests to standard ASTM G 155 have shown that Fugalite Bio fades less and keeps its colour longer when exposed to direct sunlight than other tiling grouts. The tests were conducted by CATAS, a European centre of excellence for research in the wood furnishing, industrial and environmental sector and apply to external use.


One of the problems with normal epoxy resin grouts is that they can cause contact dermatitis in the people that apply them. Fugalite Bio has been tested by the Modena and Reggio Emilia University Hospital and found to be hypoallergenic. There were no positive allergic reactions in a sample of 200 adults who suffer from contact dermatitis but had not previously been exposed to epoxy resin. Old-fashioned reaction resin grouts caused 3 – 3.5% of subjects to react. A second experiment carried out on people that suffer from dermatitis through contact with resins and amines showed that a significantly lower percentage reacted to Fugalite Bio than the comparative products (12% compared to 20% – 36%).


Tests have shown that the whole of the Fugalite Bio range meets the criteria for being classified as water resistant. However resistance to surface water absorption (water repellence) hugely reduces water absorption and Kerakoll’s research team test for this in addition to performing the standard test.

They do this by carrying out a “waterdrop effect” test using the sessile drop method, and use the norms developed by the paint and textile industries to measure the grout against.

These tests show that the grout is waterproof with water forming droplets on its surface rather than soaking into the grout. It will stand up to heavy wear and tear in damp environments.


When tested to UNI EN ISO 10545-14 (Ceramic Tiles: determination of stain resistance), Fugalite Bio was shown to resist staining from both chemicals and common household products such as coffee, oil, red wine.


Fugalite Bio has been tested by the CSTB (Scientific and Technical Centre for Building) in France, and found to restrict the growth of microorganisms without resorting to the use of harmful chemicals and so is ideal for use in damp environments.

Grouting Wood-Effect Ceramic Tiles

Using normal grout with wood-effect ceramic tiles can make it obvious that the floor is not real wood and spoil the desired effect. Twelve of the twenty-four shades of Fugalite Bio has been specifically developed for use with wood-effect tiles and becomes virtually invisible making the grout joints less obvious.

Grouting Glass Tiles & Mosaics

Resin-based grout can look better than a standard one with glass and glass mosaic tiles and will also avoid scratching the surface. Fugalite Invisible which is part of the Fugalite range is formulated for use with glass tiles. It is made from a mixture of tiny, pure glass beads and a transparent resin giving an opalescent semi-transparent appearance which renders the joint practically invisible. It works by taking the light diffused from the tiles which is reflected by the glass balls making the grout appear the same colour as the tiles.

Fugalite Bio Performance Values

Static modulus of elasticity ≈ 1230 MPa ISO 178
Resistance to abrasion ≈ 203 mm3 EN 12808-2
Water absorption after 240 min. ≈ 0,06 g EN 12808-5
Colour fastness 3.5 – 4.5 GSc (Daylight) UNI EN ISO 105-A05
Resistance to bacterial contamination class B+ CSTB 2010-081
Porcelain tiles/concrete tensile strength ≥ 2,5 N/mm2 EN 1348


Initial shear strength ≥ 5 N/mm2 EN 12003
Shear strength after water immersion ≥ 5 N/mm2 EN 12003
Shear strength after thermal shock ≥ 2 N/mm2 EN 12003


Values taken at +23 °C, 50% R.H. and no ventilation. Data may vary depending on specific conditions at the building site.

Technical Advice

If in doubt seek technical advice on what is the best product to specify for your project. Tilemaster Adhesives Limited, the Kerakoll UK subsidiary, has a team always on hand to give advice and is frequently involved in the specification process to ensure that the right products are chosen to enable the project to run smoothly and be fit for purpose when complete, please do contact them if you have any questions.