Will this blow the sand out of my joints?

It can, and that is the risk to plan around. Joint sand comes out when the nozzle is narrow, held close and pointed down into the joint; it stays when the spray is wide, held back and worked at a low angle. The paver institute puts it in exactly those terms — nozzle type, distance, angle of attack. An older patio has years of packed-in fines to lose, so it calls for more care rather than less. Where a joint is already low, tell us before the start.

Can you get the white haze off my new patio?

Tell us how new. On a patio in its first year, efflorescence is the first thing to rule out: it came out of the pavers rather than landing on them, and the paver institute says it can peak within 60 days of installation and does not affect structural performance or durability. Some of it wears off on its own. Pressure is the wrong answer here: the national concrete masonry association warns that high-pressure water drives more moisture into the material and may promote further efflorescence. So it is a purpose-made remover, or patience.

Can you wash it and seal it the same day?

No, and nobody should. The paver institute requires the cleaned surface to be completely dry and free of moisture for at least 24 hours before most sealers, and names trapped moisture and an active efflorescence source underneath among the things that turn a sealer white. Same-day sealing is how a patio can end up hazy. Rain inside that window starts it over.

My patio is a poured slab and the pool deck goes with it. Same job?

Different surfaces, different constraints. On a slab there is no joint sand to lose, but there is also no published safe pressure for poured concrete, because the point where it fails belongs to that particular slab — the driveway page is where we go into that. Some marks on a slab are the concrete itself rather than dirt sitting on it, and those do not wash off at any setting. Ask us to look at both surfaces in person before quoting.

Patio cleaning (pavers, slabs and pool decks)

A paver patio is not one surface. It is a field of separate stones held in place by the sand packed between them, and that sand is the only part of the job a pressure washer can take away for good. The paver industry publishes real numbers for this work, so on this page we can tell you what the standard actually says instead of asking you to take our word for it. Poured slabs and pool decks have limits of their own.

Stones plus sand, and the sand is the fragile half

A paver patio is a field of separate concrete stones sitting on a bed of sand, with more sand packed into every joint between them. The stones are the half that gives you the least trouble. The sand is the other half, and it is the part of the patio a wash can take away for good. The trade body that writes the standards for this pavement — the Interlocking Concrete Pavement Institute — gives joint sand a section of its own in the cleaning spec, and names aggressive cleaning among the forces that remove it. Those joints get better with age, by themselves. Fines work down into the sand over the years and pack it tighter, which is why the institute says joint sand stabilisation is generally optional and not required for many installations. Time put that stabilisation there. It also means a patio laid last spring and a patio laid twelve years ago do not clean the same way. The new one has loose sand that comes out easily. The old one has something that took years to build. If your joints are already low, tell us where, or send a photo, before anything gets wet.

A number that somebody actually published

On poured concrete there is no published safe pressure, because the point where a surface fails belongs to that particular slab rather than to the machine — the driveway page goes into that at length. Pavers are the exception, and it is worth knowing. The Interlocking Concrete Pavement Institute puts professional cleaning of interlocking concrete pavement at 1,000 to 4,000 psi and 2 to 6 gallons a minute, and in the same document says something that matters more than the range does: rinse volume counts for more than rinse pressure. The water that cleans a patio is the water that carries the loosened dirt off it, not the water that hits it hardest. That is also why the range is so wide. The stones can take it; the joints decide the job. What actually keeps sand in a joint, by the same spec, is nozzle type, how far the nozzle is held off the surface, and the angle of attack — a wide spray worked at a low angle. A narrow jet held close and pointed down into a joint empties it, faster than anybody can decide it was a mistake. So the honest version of the surface-cleaner-versus-wand argument is that the tool matters less than the nozzle, the standoff and the angle. A consistent standoff and consistent overlap are what make the finished patio read as one surface and not as a record of where the operator stood.

The white bloom is coming out of the pavers, not landing on them

White haze on pavers has an explanation with a name, and on a young patio it is the first one to rule out. Efflorescence on concrete pavers is calcium hydroxide from inside the paver, carried up to the surface and turned white there by reacting with carbon dioxide in the air. It came out of the stone rather than landing on it. Two things follow, and both are in the institute's spec. It does not affect the structural performance or durability of the pavers, so a new patio doing this is not a defective patio — it can peak as soon as 60 days after installation, which is exactly when a new owner is looking hardest at it. And some of it wears away on its own. The instinct, which is to put more pressure on it, is the one thing the national concrete masonry association warns against: applying water, and especially water under high pressure, drives more moisture into the material, and moisture is what carries the salts out in the first place. It may promote further efflorescence. When what you have is efflorescence, the answer is a remover made for the purpose, tried on a small area first, or time. Strong acid is not a shortcut either — the paver institute notes that strong acids change paver colour and can expose the aggregate.

Sealing, and the two things you are most likely to be sold

Two things get sold alongside a patio wash, and the trade body has a position on both that is worth having before somebody quotes you. The first is joint sand stabilisation. The institute's own words are that it is generally optional and not required for many interlocking concrete pavements, for the reason above — joints stabilise by themselves as fines migrate in. There are installations where it makes sense. What the spec does not say is that every patio needs it after every cleaning. The second is sealing. Sealing while the patio is clean, the same day, sounds efficient and can end with a white haze under the sealer. The institute requires the cleaned surface to be completely dry and free of moisture for at least 24 hours before most sealers go down, and lists what turns a sealer white: trapped moisture, and a source of efflorescence under the pavers still working its way up. That 24 hours is a scheduling matter rather than a formality: rain inside it starts the clock again. And on how often a sealed patio needs doing again, the institute declines to give an interval at all: it says that depends on the use, the climate and the quality of the sealer.

Common questions

Will this blow the sand out of my joints?: It can, and that is the risk to plan around. Joint sand comes out when the nozzle is narrow, held close and pointed down into the joint; it stays when the spray is wide, held back and worked at a low angle. The paver institute puts it in exactly those terms — nozzle type, distance, angle of attack. An older patio has years of packed-in fines to lose, so it calls for more care rather than less. Where a joint is already low, tell us before the start.
Can you get the white haze off my new patio?: Tell us how new. On a patio in its first year, efflorescence is the first thing to rule out: it came out of the pavers rather than landing on them, and the paver institute says it can peak within 60 days of installation and does not affect structural performance or durability. Some of it wears off on its own. Pressure is the wrong answer here: the national concrete masonry association warns that high-pressure water drives more moisture into the material and may promote further efflorescence. So it is a purpose-made remover, or patience.
Can you wash it and seal it the same day?: No, and nobody should. The paver institute requires the cleaned surface to be completely dry and free of moisture for at least 24 hours before most sealers, and names trapped moisture and an active efflorescence source underneath among the things that turn a sealer white. Same-day sealing is how a patio can end up hazy. Rain inside that window starts it over.
My patio is a poured slab and the pool deck goes with it. Same job?: Different surfaces, different constraints. On a slab there is no joint sand to lose, but there is also no published safe pressure for poured concrete, because the point where it fails belongs to that particular slab — the driveway page is where we go into that. Some marks on a slab are the concrete itself rather than dirt sitting on it, and those do not wash off at any setting. Ask us to look at both surfaces in person before quoting.

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