Why pressure is not one thing
People ask whether a surface can be pressure washed, as if the answer were yes or no. In practice three things decide it: the pressure, the distance from the nozzle to the stone, and the angle. A 2023 study published in Environmental Earth Sciences measured surface changes and volume losses on marble, limestone, granite, sandstone and tuff under different cleaning methods.2 Both high-pressure methods, with cold and with hot water, had a significantly stronger abrasive effect than steam when the distance was too small.2
So the same machine can be fine at one distance and harmful at another. That is also why the honest answer to “is it safe?” is “at what setting, by whom, and on which stone?”. A UK council’s advice on cleaning historic buildings puts the general rule in one line: the softer the stone, the greater the risk of damage when cleaning.3
Surface by surface
| Surface | Pressure washing | Watch out for |
|---|---|---|
| Marès, walls and paving | Avoid close-range high pressure. Low pressure, wide fan, or by hand | Grains washing out, a furred surface, faster weathering |
| Old lime pointing | Low pressure only, or keep clear | Joints emptied by the jet |
| Limestone and sandstone | With care: a test patch, distance, low setting | Visible stripes and lost surface |
| Polished marble | Generally no | Lost polish, and acid leaves marks |
| Terrazzo | Rarely needed. Scrub with a suitable cleaner, rinse with plenty of water | Acids, harsh alkalis, salts; water can lift some sealers |
| Granite and hard paving | Usually fine | Failed joints and loose slabs |
| Sound concrete | Usually fine | Stripes if passes overlap unevenly |
| Tile | Usually fine on the tile | Weak grout and loose edges |
This table is our working judgement from the sources in this guide. It is a guide, not a substitute for looking at your own stone. Two stones with the same name can behave quite differently.
Marès, in particular
Marès is Mallorca’s own building stone, a calcarenite that gives so many of the island’s houses their honey colour. The research describing it calls it highly porous, generally very soft and of very low compressive resistance compared with other stones used in construction. It also says hardness varies a great deal from one type to another, and that some recrystallised types can be really hard.1
For you that means three things. It marks easily, so a narrow jet can leave a groove you will see for ever. It drinks water: its open, connected pores take it in fast,1 so a soaking can carry whatever is dissolved in the water into the stone. The dark surface you are trying to remove may be partly the stone’s own weathered skin, and cleaning can change how a stone goes on to weather: conservation advice asks you to weigh that before you start.3 And look at the joints, because too much water can wash them out.3
So start gently. Brush off what is loose, using a soft bristle brush and plain water, with a low-pressure rinse if you need one. Consider leaving a little patina: a marès wall is allowed to look its age. For a listed or historic building, talk to a conservation specialist before you do anything. We price marès separately from ordinary terraces, at €29 per m² against €14 per m² for a terrace, patio or path, because it is slower and more careful work.
Terrazzo
Terrazzo’s enemy is chemistry more than pressure. Terrazzo contractors following the trade association’s guidance warn against harsh alkalis and acids, and against all-purpose cleaners containing soluble, crystallising salts. They ask for cleaners in a neutral range, with the floor kept wet during cleaning and rinsed with plenty of clean water, and they note that even standing water can dissolve some sealers.4
So do not reach for vinegar, a limescale remover or bleach on a terrazzo terrace. Indoors there is hardly ever a reason to bring a pressure washer near it, and water finds its way under skirting and thresholds. Outdoors, scrub and rinse first, and only then ask whether pressure would add anything.
Before anyone starts
- Find out what it is. If you do not know the stone, ask whoever laid it, or take a good photograph to someone who does.
- Walk the surface. Look for loose slabs, hollow-sounding spots, failed pointing and old sealant. These come away under a jet, whatever the setting.
- Decide where the water goes. Dirty run-off should not end up in the pool, in a neighbour’s garden or under a door.
- Try a hidden patch and let it dry completely before you judge it. Wet stone always looks better than it is.
- Protect what is nearby: plants, doors, window seals and anything electrical.
What it cannot do
A pressure wash does not remove everything. Rust marks, oil that has soaked in and old paint usually lighten rather than vanish. Worn or pitted stone stays worn, and clean stone can make old repairs more visible. A careful firm says so first. Ours does the same: a surface check, a pressure suited to the surface and, where a surface will not take it, a plain no.
Because surfaces differ so much, we quote this work in writing. Your area in square metres and your postcode give you an estimate on screen, the visit has a minimum of €149, and the written quote is the price. If you are not sure what you have, send a photograph with the quote request and we will tell you what we think before anyone unpacks a hose.