How to clean and maintain your granite paving to prevent problems such as weeds, moss, algae and lichen and how to remove them if they become established.
Natural stone is low maintenance but don’t skimp on the essentials
Natural stone is rightly trumpeted as being a low maintenance option for paving, but that’s not to say it’s ‘no maintenance’. So long as you adhere to a regular basic maintenance regime, the good news is you shouldn’t be spending hour after hour keeping your granite paving in pristine condition.
Along with basic dirt accumulating, other ‘nasties’ such as weeds, algae and lichens can take hold over time if preventative cleaning and sweeping isn’t carried out. The old saying ‘prevention is better than cure’ is certainly valid when it comes to basic granite paving maintenance.
Sweeping and cleaning
Along with keeping the paving clear of loose dirt particles, leaves and other debris, regular sweeping will help prevent weeds from becoming established. Weeds often grow into the joint from on top, not always up and through it from below as commonly believed, so regular attention with a stiff bristled broom will pay dividends.
If your paving or hard standing receives regular traffic whether foot or vehicular, then this in itself can inhibit weeds to a certain extent.
For regular cleaning, a simple solution of soap and water worked over your granite paving with a stiff broom will suffice followed by rinsing with clean water.
Washing up liquid or a floor cleaning product will be fine as will Jeyes Fluid. Check the wording on the container – if there’s any reference to ‘not suitable for natural stone’ or similar then don’t use it, and make sure it’s acid free as this can spell disaster for natural stone.
Once you’re set up with your bucket of soapy water and a brush, then it’s old fashioned elbow grease to scrub away the dirt and detritus from your granite paving. To finish, rinse with clean water; a hose is fine but be careful not to direct it at the joints between slabs as this can weaken them.
Another word about cleaning products; be careful if you’re thinking of using a ‘patio cleaner’ or similar. Many of these contain acid, so check the ingredients on the container carefully if you’re tempted to try one.
Removing weeds and other remedial work
If you’ve neglected your cleaning duties you may find one or more of the following have taken hold on your granite paving:
Manually – you can either gently pull weeds away from the joint they’re growing in or scrape them off using a garden hoe or similar implement. If weeds have become established, some of the jointing material may come away as you remove them, so this will need replacing as soon as practical.
Weedkillers – an appealing option to save on the manual option above, but use weedkillers with care. Types designed for use with gardens and paving are best as they’re formulated to target the weeds so shouldn’t discolour the paving or harm nearby plants and grassed areas.
Using sealants – they can help prevent weeds growing into the joint but aren’t foolproof; any dirt and detritus that settles onto the sealant provides an environment for weeds to grow, so regular basic sweeping is still necessary.
Algae is prevalent in the atmosphere in the form of spores and, when they settle on a damp and permeable surface, breed and show up as the green patina on your stone.
To remove it use a basic household bleach diluted with water in equal parts and apply with a watering can, or simply distribute it across the granite with a brush. Leave it for a few moments to go to work on the algae then rinse away with plenty of water; you may have to repeat the procedure a few times to get rid of more established algae.
If your granite is susceptible to algae (it tends to affect wetter areas so your geographical location and whether your paving is in a damper area will be determining factors) then the above procedure may stop algae establishing itself to start with.
Lichens are a fungus and appear as undesirable spots on your granite surfaces often black, white or greyish in colour.
They can be very difficult to remove; they penetrate the surface layer of the granite, so usually the only way to remove them is with a bleach solution, a stiff scrubbing brush and plenty of elbow grease.
Repeated cycles of scrubbing will likely be required and even then it’s possible the surface may be altered in some way either through the lichen chemically altering the pigmentation of the slab, or through your vigorous brushing.
Moss is familiar enough to many, and forms when dirt and detritus has accumulated in the joints between slabs.
Unlike lichens and more advanced algae attacks, moss doesn’t penetrate the stone itself so should be more easily removed by basic scraping or maybe a vigorous sweep with a stiff brush.
If you decide to try a liquid removal method, be very wary of specific moss killers; they may remove the moss but can also discolour your paving (the inclusion of ferrous sulphate in some products causes the discolouration so check the ingredients list).
A standard weedkiller will do the job although preventing moss in the first place with a bleach and water treatment as in the case with algae removal will be ideal. The key though is to keep the areas moss likes to establish itself in – namely the nooks and crannies in the joints – clear of detritus.
Prevention is key
As you’ve seen, some basic prevention can save a whole lot of hard work later in removing pests such as moss and lichen. Yes, natural stone is low maintenance, but a few minutes regularly will save time in the long run.