Key points
- CG = cementitious grout, RG = reaction resin (epoxy) grout. Cementitious grout has two classes: CG1 normal and CG2 improved.
- CG1 and CG2 differ in only two tests: abrasion resistance (≤ 2000 vs ≤ 1000 mm³) and water absorption (≤ 5/10 g vs ≤ 2/5 g).
- Additional letters: W reduced water absorption, A high abrasion resistance, F fast.
- Epoxy grout RG: water absorption ≤ 0.5 g after 240 minutes and abrasion ≤ 250 mm³ — best for commercial kitchens and hygiene areas.
Grout is the material that fills the joints between tiles. The wrong choice means joints that darken quickly, crack, or absorb water in bathrooms. The European standard EN 13888 classifies it as follows.
1) Types and classes
| Code | Meaning |
|---|---|
| CG1 | Normal cementitious grout1. |
| CG2 | Improved cementitious grout: higher abrasion resistance and lower water absorption1. |
| RG | Reaction resin grout (usually epoxy) that hardens by chemical reaction, with a single class1. |
Optional letters are added to cementitious grout: F fast setting/drying, A high abrasion resistance, W reduced water absorption. Example: CG2WA means improved cementitious grout with reduced water absorption and high abrasion resistance1.
2) The requirements in numbers
| Property (test method) | CG1 | CG2 | RG (epoxy) |
|---|---|---|---|
| Abrasion resistance (EN 12808-2) — lower is better | ≤ 2000 mm³ | ≤ 1000 mm³ | ≤ 250 mm³ |
| Water absorption after 30 min (EN 12808-5) | ≤ 5 g | ≤ 2 g | — |
| Water absorption after 240 min | ≤ 10 g | ≤ 5 g | ≤ 0.5 g |
| Flexural strength (EN 12808-3) | ≥ 3.5 N/mm² | ≥ 3.5 N/mm² | ≥ 30 N/mm² |
| Compressive strength | ≥ 15 N/mm² | ≥ 15 N/mm² | 45 N/mm² |
| Shrinkage (EN 12808-4) | ≤ 2 mm/m | ≤ 2 mm/m | ≤ 1.5 mm/m |
Source: technical bulletin TDS 137EN1. Note that CG1 and CG2 are identical in strength and shrinkage; the difference is only in abrasion and water absorption.
3) Which to choose?
- CG1: MAPEI's guide considers it adequate for tiles in residential and commercial environments not exposed to severe temperature and humidity changes2.
- CG2 (especially CG2WA): recommended by the same guide for areas with high humidity, thermal shock or intense traffic, conditions typically found in high-intensity commercial and industrial environments2.
- RG (epoxy): when you need the lowest absorption, highest chemical resistance and easiest cleaning: commercial kitchens, hospitals, pools, showers. It costs more and needs skill and speed because it hardens chemically.
4) How much grout do I need?
MAPEI publishes, in its Ultracolor Plus technical data sheet, a consumption formula based on tile size and thickness and joint width3:
Dimensions are in millimetres, and the joint depth equals the tile thickness. The data sheet uses the factor 1.6 for this product; it varies by product, so take it from your grout's data sheet. Example: 60×60 cm tiles 10 mm thick with a 3 mm joint → about 0.16 kg/m²; the data sheet table gives 0.2 kg/m² for this size after rounding. Try the grout calculator in the tools section.
5) Application tips
- Don't start grouting before the adhesive's cure time on its data sheet.
- Clean adhesive out of the joints to sufficient depth before grouting.
- Tiles with deliberate crazing are wetted before grouting and not used with coloured grout4.
- Movement joints (at walls and changes of plane) are filled with a flexible sealant like silicone, not grout. See joint sealants.
Sources
The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.
- 1EN 12004 Classifications – TDS 137EN — LATICRETE International
- 2Grouts and sealants for installing ceramic tiles and stone material — MAPEI
- 3Ultracolor Plus — technical data sheet (consumption table and the formula used to calculate it) — MAPEI Australia — technical data sheet
- 4Application Technique — Terms and Classifications according to DIN EN 14411 — AGROB BUCHTAL / Deutsche Steinzeug