.jpg)
Why the material matters so much
In our article on re-bedding gresite we explained when it needs doing and what the process involves. But most of the detached tiles we repair on the Costa Blanca are not caused by the gresite itself, but by the wrong adhesive or grout, or a rushed application. A pool is submerged all year, exposed to temperature changes, chlorine or salt and water pressure: not just any tile adhesive will do.
The adhesive: which one to use
Tile adhesives are classified under the EN 12004 standard. For pools, the recommended minimum is an improved cementitious adhesive C2, with these additional properties:
- T (reduced slip): tiles don't slide down vertical walls.
- E (extended open time): more time to place the mosaic before the adhesive skins over.
- S1 or S2 (deformable or highly deformable): absorbs the expansion of the pool shell caused by sun and temperature changes.
For glass gresite, which is translucent, use white adhesive so it doesn't darken or stain the colour of the mosaic. In especially demanding areas (spas, very warm pools, repairs where you can't wait long) an epoxy adhesive (R2) can be used: more expensive and harder to work with, but with superior bond strength and chemical resistance.
Grout: the forgotten part
Grout is what stops water getting behind the tiles. If it degrades, water attacks the adhesive and the gresite eventually comes loose. Under the EN 13888 standard, there are two options for pools:
| Material | Classification | When to use it |
|---|---|---|
| Improved cementitious adhesive | C2 TE S1 / S2 | The usual choice for bedding gresite in pools |
| Epoxy adhesive | R2 T | Spas, warm water and areas with high chemical demands |
| Improved cementitious grout | CG2 WA | General use; low water absorption and high abrasion resistance |
| Epoxy grout | RG | Maximum durability: non-porous, resists chlorine and salt, doesn’t blacken |
Epoxy grout costs more and needs an experienced applicator, but it lasts much longer and needs almost no maintenance. For salt-chlorinated pools or pools with recurring grout problems, we usually recommend it.
How to apply it properly
- Sound, clean substrate: no dust, limescale, algae or loose mortar, and any cracks or leaks repaired before bedding.
- Suitable conditions: avoid direct midsummer sun, wind and extreme temperatures; on hot days the substrate is dampened, without leaving standing water.
- Fine notched trowel: gresite needs a thin, even bed. Too thick a layer shows through the glass and leaves voids.
- Respect the open time: spread only the area you can cover in a few minutes. If the adhesive no longer sticks to your finger, it has skinned over and must be removed and spread again.
- Press and align the sheets with a rubber float, making sure each tile is fully in contact with the adhesive.
- Grout at the right time, once the adhesive has set according to its data sheet, filling the joints fully.
- Curing before filling: depending on the product and temperature, usually between one and three weeks. Filling too early is one of the most common causes of failure.
Paper-faced or mesh-backed gresite
Gresite comes in sheets, either with paper on the visible face or with mesh or bonding dots on the back. For pools we usually prefer paper-faced sheets, because the adhesive grips the whole back of each tile. Some mesh-backed sheets reduce the contact area and come loose sooner under water.
Mistakes that make gresite fall off again
- Using interior or C1 adhesive, designed for tiles that won't be submerged.
- Bedding onto old gresite or a dirty substrate, or without first repairing the crack or leak that caused the problem.
- Working in full summer sun, with the adhesive drying before the tiles are placed.
- Leaving empty or poorly filled joints that let water in.
- Filling the pool too soon or immediately applying an aggressive shock treatment.
- Draining the pool in summer or leaving it empty for a long time: the shell expands in the sun and the lining suffers.
How to make the repair last
Once repaired, the main enemy of gresite and grout is unbalanced water. Low pH or water with low calcium hardness becomes "aggressive" and slowly dissolves cementitious grout; very scale-forming water, common with Alicante's hard water, leaves limescale on the mosaic. Keeping pH between 7.2 and 7.6 and alkalinity and hardness within range protects the lining for years. If you need help, our water treatment service takes care of it.
At AquaGarden Alicante we re-bed gresite with adhesives and grouts designed for permanent immersion, and advise you on whether a spot repair or a complete relining makes more sense. Ask for a free, no-obligation quote or see our pool repair service.