No matter how well a pavement might be laid, and no matter how much was spent on quality materials, all pavings, from the very top-of-the-range to the not-quite-so-good, require some basic maintenance to keep them looking their best. Those contractors that promise “maintenance-free” paving of one form or another are misleading. Maintenance keeps paving in prime condition: lack of maintenance allows paving to deteriorate.
Even if it’s just a basic wash-down with soapy water, all types and forms of paving will look so much better for it, while certain types of paving tend to need a bit more care and attention to ensure they always look as smart as possible. The good news is that cleaning is usually easy and even the most decrepit, neglected or abused pavement can often be given a new lease of life with just a little effort.
The simplest and safest way to clean paving is to scrub it with soapy water. Some people will swear that hot soapy water is more effective than cold, but in reality, ANY soapy water will do. Use wash-up liquid or an acid-free soap-based floor cleaning product. If there is any hint of a warning about use of the particular product with limestone or marble floors, put it back under the sink and find summat else. Acids and acid-based cleaners can have a deleterious effect (some would say an horrific effect) on certain types of concrete and natural stone paving, as will be explained later.
Other than a bucket or pail in which to keep the soapy water, the only equipment needed is a stiff brush, that is, one with tough, rough, thick bristles rather than the finer bristled types which we refer to as ‘soft brushes’. Incidentally, “daft” is an olde-englyshe word meaning “soft”, hence the expression “as daft as a brush”. However, a “daft” brush is not what is needed for cleaning – make sure the brush being used has stiff, rugged bristles and isn’t in the least “daft”.
The soapy water can be swilled onto the surface of the paving and then, with brush in hand, it’s simply a matter of scrub, scrub, scrub, using the mechanical action of the brush in combination with the chemical action of the soap to loosen any surface detritus. It’s been noted that this is particularly good exercise for shiftless or truculent teenagers, although some form of monetary incentive is usually required. I’m happy to let them do it for free, but if they insist on crossing my palm with silver, I wouldn’t want to offend them by refusing!
Wash off the loosened dirt with clean water, again using a bucket or pail to swill it across the pavement, taking all the muck with it. A hose can be used if preferred, but, as will be repeated on more than one occasion in what follows, care must be taken to ensure the jointing, in whatever form it might be, is not loosened or removed.
As mentioned above, acid-based cleaning products should be avoided whenever possible: for many types of paving, they do more harm than good. In particular, watch out for “Brick Cleaning Acid”, or any “patio cleaner” that has hydrochloric acid listed in its ingredients. They may clean your paving, but there’s also a significant risk that they’ll ruin it.
Most granites, basalts, porphyry, slates and quartzite seem to be unaffected by acid or acid-based cleaners, but process with caution and test a small discreet area first.
York Stone, Pennant Stone and Liscannor are variable: some pieces will exhibit no reaction to acid or acid-based cleaners, while others will turn orange. It’s related to the iron content, and as this varies from stone to stone, it’s best to test before committing larger areas to acid cleaning
Indian sandstones, Limestones, Marble and Travertine: avoid like the plague. Many of the paler Indian sandstones exhibit a violent rusty reaction to acid, although the extent of the reaction does vary from stone to stone and from quarry to quarry. Limestone is dissolved by hydrochloric acid – one of the definitive tests used by geologists to confirm a particular rock as a limestone is the effervescent reaction to hydrochloric acid. Marble and travertine are metamorphic limestones, so they, too, are best kept well clear of acids.
Plain, uncoloured concrete is ‘etched’ by washing it with hydrocholric acid. The acid ‘eats away’ at the top few microns of the concrete surface to reveal a pristine surface beneath. While this may be great for cleaning up dirty or discoloured concrete, it is less successful when used on coloured concrete, which uses dyes based on iron oxide to create various colours within the concrete. The acid reacts with the iron oxide and can have a dramatic affect on the shade, turning buffs, soft reds and browns into strong orange or tan hues.
As more and more patio owners have come to realise, some of the imported sandstones (and, to a slightly lesser degree, some of the imported limestones) seem to become covered in a greenish growth almost as soon as the cheque has cleared. Sadly, far too many contractors and many of the importers/distributors are less than forthcoming with information on what it is, why it’s happening, and how it can be removed. There is, as is to be expected with a natural material, significant variation in where, when and how badly it can appear, but it’s safe to say that it’s more prevalent in wetter western half of both major islands. So, we see more of it in Galway than we do in Dublin, and more in Southport than in Southend.
The green is an algae. It is ubiquitous in the environment, floating around as spores and looking for a damp-ish and permeable surface where it can set up camp, invite a few of the relatives to move in locally, and set about breeding. Algae are colonies of very simple plants. They eke out an existence by finding a home where the rainwater can dissolve a smattering of basic minerals from the substrate, which they then absorb and use to promote their growth. As long as they remain as simple algae colonies, they are fairly simple to shift, and one of the best ways of evicting them from the surface of any paving material is to use bleach. algae on sandstone.