Concrete and stone paving
A hard outdoor surface whose weak point is not the slab but the JOINTS between slabs — which is why the standard advice to blast it with a pressure washer is fenced by an angle.
Precautions
- Test on an inconspicuous area first
- Wear gloves
- Dispose of responsibly
In detail
Paving is durable and the manufacturer says so, and almost every way of damaging it while cleaning goes through the same route: the jointing material. The routine is brushing. Where colour is masked, scrub with warm water and washing-up liquid or an ACID-FREE soap-based cleaner, then wash off until ALL the soap has gone, channelling the run-off to a drain rather than onto planting. Pressure washing is permitted and fenced, and the fence is geometric. Used to excess it shortens the paving's service life. The lance is never pointed straight down, because that lifts the jointing material out; it is held at a SHALLOW ANGLE of no more than thirty degrees across the diagonal rather than along the joints; the setting is low; and the joints are INSPECTED AND REFILLED afterwards, because empty joints are bad for the pavement itself. Acid is the other escalation and it is decided by the stone. Granites, basalts and slates are unaffected. Sandstones vary and some turn ORANGE, because of the iron in them. Limestone and marble must never be acid cleaned — hydrochloric acid dissolves them, which is the same chemistry this catalogue records for a marble worktop indoors.
Why
- Concrete and stone paving is explained by Porous and non-porous surfaces
Related
- Concrete and stone paving is commonly affected by Algae
- Concrete and stone paving is commonly affected by Oil and grease on textile
Sources for this page
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That routine cleaning is brushing and warm soapy water with an acid-free cleaner rinsed until all soap is gone, that the power lance is held at no more than thirty degrees across the diagonal and never directed down because that loses jointing material, that joints are inspected and refilled afterwards, and that acid must not be used on limestone or marble. (states this directly)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
What CleaningHQ cannot answer yet
These are recorded questions about this subject that we have not yet researched to a standard we would publish.
- Removing oil from concrete or hard outdoor and garage surfacing
Last reviewed by a person on .