First: where is the water getting in
Before choosing a system you need to know what is failing, because the answer changes completely.
- **Open joints between tiles** or perished grout. Water goes through and pools underneath.
- **The junction with the wall.** This is the single most common failure point: water sneaks in behind the skirting or at the joint with the wall.
- **A badly finished drain**, or one with less fall than it should have.
- **The membrane underneath, worn out.** If the terrace is thirty years old, this is the most likely cause.
- **Cracks** in the surface, from movement or from missing expansion joints.
A useful clue: if the stain below always appears in the same place and lines up with a wall, it is almost certainly the junction and not the whole surface.
Without lifting the floor
If the tiling is sound and well bonded, there are two routes that avoid major work.
**Liquid polyurethane membrane.** Rolled straight onto the existing tile after cleaning and priming, it forms a continuous, elastic skin. It is the most used option today: no joints, it follows corners and drains, and it copes well with movement. It needs two or three cross-laid coats and, if it will get heavy foot traffic, a protective top coat.
**Flexible waterproofing mortar.** Applied with a trowel or brush, in two coats with reinforcing mesh at the junctions. It leaves a harder finish than polyurethane and can be tiled over.
In both cases the rule is the same: the waterproofing **has to run up the wall** by at least 15 or 20 centimetres, and go properly into the drain. What fails is almost never the middle of the terrace, it is the edge.
Lifting the floor
If there is widespread damp or the tiling is loose, there is no shortcut. Everything comes off and is rebuilt:
- Break out down to the structural slab and clean it.
- Form the **falls** in mortar: between 1% and 2% towards the drain. A flat terrace always ends badly, however good the membrane.
- Lay the waterproofing, usually a torched asphalt sheet, running up the perimeter.
- Protect it with a mortar screed and lay the new floor.
Expansion joints
A terrace in the sun expands and contracts every day. Without joints the floor tents or blows, and the waterproofing underneath goes with it.
You need a joint all the way round the perimeter, against the walls, and intermediate joints dividing the surface into bays of about 15 to 20 square metres. They are not optional.
What to bear in mind in Menorca
**The sun.** A dark finish can exceed 70 °C in summer. The lighter it is, the less movement and the less work for the material.
**The salt.** Near the sea the air attacks mortars and reinforcement. Choose products rated for marine environments, and do not skimp on finishing the perimeter.
**When to do it.** Not with rain forecast in the next 24 to 48 hours, and not in full August sun with the surface baking: the product dries before it cures. Spring and autumn are the good seasons.
Mistakes that keep happening
- Not running up the wall, or running up three centimetres.
- Skipping the primer on ceramic, which is a low-absorbency surface and needs a bonding coat.
- Applying one thick coat instead of two thin cross-laid ones.
- Leaving the drain unfinished, which is where the water ends up getting in.
- Forgetting the falls and leaving a permanent puddle.
- Waterproofing over a surface that moves, without first fixing whatever is moving.
We will tell you what you need
Tell us the area, whether you are lifting the floor or not and where the stain shows, and we will tell you which system fits and how much material it takes. We stock sheet membranes, polyurethanes, waterproofing mortars, mesh and drain fittings.