Key points
- EN 14891 classifies liquid-applied waterproofing under tiles as CM cementitious, DM dispersion, RM reaction resin.
- All types must be watertight, achieve adhesion ≥ 0.5 N/mm² after water, heat and lime exposure, and bridge cracks ≥ 0.75 mm.
- Class P: resistant to chlorinated water (pools). Class O: crack bridging at low temperature.
- The waterproofing must be tested (flood test) before tiling.
One of the most common renovation problems: damp in the wall of the room next to the bathroom, or a leak into the ceiling below. The cause is often the false belief that tiles "waterproof". In fact cement grout absorbs water (at rates set by the standard)1, and water finds its way through joints and cracks. The solution is a waterproofing membrane under the tiles.
1) Types of liquid-applied membranes (EN 14891)
| Code | Type | Description |
|---|---|---|
| CM | Cementitious | Hydraulic binders (cement) with aggregates and polymer additives, mixed with water or a special liquid before use1. |
| DM | Dispersion | Organic binders as an aqueous polymer dispersion with additives and fillers1. |
| RM | Reaction resin | Synthetic resin with fillers that hardens by chemical reaction1. |
2) Basic requirements for all types
| Test | Requirement |
|---|---|
| Initial tensile adhesion (after 28 days) | ≥ 0.5 N/mm² |
| Adhesion after water contact (21 days immersion) | ≥ 0.5 N/mm² |
| Adhesion after heat ageing (14 days at 70°C) | ≥ 0.5 N/mm² |
| Adhesion after freeze–thaw cycles (25 cycles) | ≥ 0.5 N/mm² |
| Adhesion after immersion in lime water (7 days) | ≥ 0.5 N/mm² |
| Watertightness | No penetration allowed |
| Crack bridging under standard conditions | ≥ 0.75 mm |
Source: technical bulletin TDS 137EN1.
3) Additional classes
- P: adhesion ≥ 0.5 N/mm² after a 28-day cure including 7 days immersed in chlorinated water, i.e. resistance to contact with chlorinated water1.
- O: crack bridging at low temperature (−5°C)1.
Example: CM OP = a cementitious liquid membrane that bridges cracks in the cold and resists chlorinated water.
4) Where must you waterproof?
- The whole bathroom floor, turned up the walls (higher in the shower area).
- Kitchen and laundry floors.
- Tiled balconies and roofs.
- Pools and water tanks (with class P).
Upstand heights on walls and corner details are set by the designer, the product data sheet and the adopted code.
5) Details that make the difference
These are accepted professional practices in under-tile waterproofing systems; the final reference is the installation data sheet of the product used:
- Corners: reinforced with a dedicated flexible tape where floor meets wall and between walls.
- Pipe outlets and drains: treated with dedicated collars from the same waterproofing system.
- Thickness and number of coats: per the data sheet; usually two coats applied crosswise.
- Flood test: after full drying, plug the drain and flood the surface for a period set by the supervisor, watching the ceiling below before tiling.
- Compatibility: use an adhesive compatible with the membrane (preferably from the same manufacturer).
6) Layers and failure points by location
A simplified bottom-up layer order for a tiled bathroom or balcony floor (the actual system follows the design and product sheet):
| Layer | Function | Common failure point |
|---|---|---|
| 5. Tiles and grout | Finish | Tiles and grout are not waterproofing; water passes through them |
| 4. Adhesive | Bonds the tiles | Adhesive not compatible with the membrane |
| 3. Membrane (EN 14891) | Stops water penetrating | Corners, pipe outlets, the drain, and insufficient thickness |
| 2. Screed to falls | Directs water to the drain | A reverse fall that traps water |
| 1. Slab | Structural base | Cracks that move more than the membrane can bridge |
| Location | What is specific | Details |
|---|---|---|
| Bathroom and shower | Membrane turned up the walls, especially in the shower | bathroom renovation |
| Balcony | Sun and rain exposure; the door threshold is critical | exterior finishes |
| Pool | A class P membrane resistant to chlorinated water | pools |
| Roof | Usually roof membrane systems, not under-tile membranes | roofs and slabs |
There is no "leak-proof guarantee" just because there are tiles, grout or a single product; the complete system with its details and a flood test is what prevents leaks.
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