BEFORE
AFTER
TERRACE AND EXTERNAL PAVING CLEANING
Paving with algae on it does not just look dark. It is slippery.
External paving is porous: it takes up water, holds dirt and gives moss, algae and limescale something to grow on. After a few winters the terrace changes colour — and once it is wet, it has less grip than it had. We wash at a pressure matched to the material, treat the growth at the root and carry the dirty water off the paving rather than into the nearest drain.
Site visit and quote with no obligation. We reply within 24 working hours.
What the service covers
A survey of the paving, recording the condition of the slabs, the joints and the drains
Protection for furniture, planters, equipment and openings before any water is turned on
Dry removal of leaf litter, built-up soil and loose debris
A pressure test in an out-of-the-way spot, to settle the setting that cleans without opening the surface
Washing of the full area, including steps, thresholds, skirtings and the junction with the walls
Moss and algae treatment wherever growth is visible, to hold off its return
Clearing and cleaning of the terrace drains and gutters
Dirty water directed and collected, with the paving handed over rinsed down
Final before-and-after photographic report
SIGNS
When it is time to wash the terrace
External paving goes off slowly, and always in the same places: where the sun never reaches, where water stands and where leaves gather. By the time the staining is visible from the street, the biofilm has been building for several winters.
01Dark or greenish staining that always returns to the same areas, in shade or against the walls
02Paving that turns slippery after rain, after watering or in fog
03A whitish crust and limescale deposits on the slabs that scrubbing no longer shifts
04Joints full of soil and moss, with weeds coming up between the units
05Water still standing hours after rain — a blocked drain, or a fall that has been compromised
06A communal terrace coming into its season of use, or a building inspection due
07More than two years since the last wash, on a terrace under trees or in permanent damp
PROCESS
How we work
01
Survey and pressure test
We identify the paving material, the state of the joints and the route the water takes. Then we test in an out-of-the-way spot: what matters is the lowest pressure that cleans, not the highest the machine will give.
02
Protection and dry removal
Furniture, planters, equipment and openings are protected or moved. Leaf litter, soil and loose debris come off dry first — under water they spread across the whole area and end up in the drain.
03
Washing and treatment
Washing bay by bay, in one direction and at the distance settled in the test, so no pass leaves a mark. Where there is moss and algae, the treatment follows, going after what is left gripping the porosity.
04
Water collected, checked and reported
The dirty water is directed and collected, not pushed into the nearest drain with the muck still in it. At the end we clear the drains and gutters, rinse the paving down and walk the terrace with the client, handing over the before-and-after photographic report.
ON SITE
The stages, on the same terrace
PROJECT
The same terrace, before and after washing
The slabs were evenly darkened, with a whitish crust across the most exposed areas and moss established in the joints. The terrace was washed bay by bay, at the same pressure from start to finish so no pass would leave a mark. What you see on the right is not new paving: it is the colour that was underneath.
TWO DIFFERENT THINGS
If water is already reaching the floor below, washing will not fix it.
Washing brings the colour back to the slabs and takes away what makes them slippery. It does not close an open joint and it does not replace a membrane. Where there is a stain on the ceiling of the flat below, the problem is in the waterproofing layer under the paving — and that is not treated with water and pressure. In that case we say so at the visit, and show you where it is, before there is any quote for washing.
Cleaning: treats the surface of the slabs, the joints and the drains
Waterproofing: rebuilds the barrier that sits beneath the paving
Too much pressure on a porous slab opens the surface and brings the dirt back sooner
Joints stripped out by the lance let water in where it never got in before
HOW WE WORK AT HEIGHT
A terrace is a floor — right up to the edge.
Washing paving looks like ground-level work, and it is, until the strip along the balustrade and the junction with the wall, which are where the lance has to reach and where the slab runs out. On that strip the team works tied on, and on roofs with no access from inside it is rope that gets the machine up there in the first place.
A working line and a safety line, on independent anchor points
IRATA-certified technicians, with a Level 3 supervisor on site
A method statement, risk assessment and rescue plan written for the project
The area below cordoned off for as long as there is a team, a machine and water above
TRANSPARENCY
Timescales and what drives the quote
Typical timescale: the terrace of a house is normally washed and treated inside a single working day. On an accessible roof terrace serving a block, with several areas split by steps and low walls, allow 2 to 4 days — the moss treatment means going back over the paving once the slabs have dried.
QUOTE FACTORS
Area of the paving and the number of bays split by steps, low walls or planters
Material and condition of the slabs: the more porous and the more colonised, the slower the pass
Whether moss and algae treatment is needed on top of the washing
Whether there is a water and power supply on the terrace level itself
Furniture, washing lines and equipment to protect, move and put back
Getting the equipment up to the terrace, particularly in buildings with no lift
We give a preliminary figure from photographs, and a fixed quote after a site visit — always free of charge.
Related services
Roof waterproofing
Once water is reaching the floor below, the problem is beneath the paving.
See service →Roof cleaning
Moss and lichen on the tiles feed the dirt that washes down onto the terrace and into the gutters.
See service →Facade and glass cleaning
Glass balustrades, glazing and external walls, dealt with on the same access.
See service →Frequently asked questions about terrace cleaning
Will the pressure damage the slabs?
It will, at the wrong pressure. External paving is porous, and a lance held too close or turned up too high opens the surface and strips out the joints — the terrace then dirties faster than before, and carries pass marks that never come out. That is why the pressure and the distance are settled by a test in an out-of-the-way spot before any of the paving is started.
Why does the paving go slippery?
It is not the slab: it is the biofilm growing on it. Algae and moss form a layer that, once wet, has very little grip — and that is where falls happen on terraces and external steps. In a communal space that is a safety matter, not just a question of appearance: it is usually the argument that decides the residents' meeting.
How long before the dirt comes back?
It depends on the exposure. A terrace in full sun, with no trees over it, holds up well for two to three years. In shade, next to planting or in permanent damp, the growth reappears sooner. The treatment applied at the end of the wash holds off the return; without it, whatever is left gripping the porosity grows back in the first winter.
Where does the dirty water go?
It is directed and collected, not pushed into the nearest drain. What comes off the slabs is soil, moss and crust: send it down the pipe in bulk and it settles there and eventually blocks it. Debris comes off dry wherever possible, and the drains and gutters are left clear at the end of the works.
Does the terrace have to be cleared?
The paving has to be clear. Furniture, pots and washing lines are moved or protected — we do that at the start and put everything back at the end. If there are fixed, heavy or fragile items, it is better to know at the site visit than on the day of the works.
Can it be done at any time of year?
The washing, yes. It is the moss treatment that needs a few hours without rain after it goes on, or it washes off before it can work. In Portugal that rarely stops the job, but it does govern the day we book.
Do you also do balconies and external steps?
Yes. It is the same work and the same decision about pressure: balconies, external steps, courtyards, communal access areas and roof terraces. On balconies with glass balustrades, cleaning the glass can be done the same day.
Send us photographs of the paving and of the darkest areas.
With photographs of the terrace, the joints and the drains we can give you a preliminary figure before the site visit even happens.
+351 933 369 927