What are the white spots on my driveway?

If you have an older driveway that was laid some years ago and is covered in white spots, the culprit is almost certainly going to be lichen. Lichens are a complex life form comprising of three different organisms in a symbiotic relationship. They take at least two years to emerge on new or cleaned and sanitised driveways. They spread through the air as pieces break off and then land on another part of the surface. They grow and spread very slowly for several years however once established growth accelerates, the spots get bigger and then they can quickly spread to colonize the whole driveway. Lichen will thrive in damp and shady conditions so a driveway covered in dirt, moss and weeds will provide lichen with the ideal conditions to grow.

Will lichen damage my driveway?

Lichen will not cause damage to your driveway. However, they do look unsightly and can become slippery in Winter and wet conditions.

How to remove white spots lichen from a Driveway

There are 3 main techniques that can used to remove white spot from a driveway.

1. Pressure Cleaning

Using a pressure washer to clean your driveway will remove most of the white spot lichen. It will also remove dirt, moss and grime which all contribute towards keeping the surface of your driveway damp and shaded – ideal conditions for lichen to thrive. On concrete drives such as block paving a pressure of 2500 to 3000 psi would be ideal. Removing lichen from tarmac will require a pressure around 2000 psi. However, established lichens can be deeply embedded into the driveway surface so traces of the lichen may remain after pressure cleaning and the white spots will begin to reappear within a few months or even weeks. Therefore for more most effective and long-lasting results, a chemical solution should also be applied to make sure all traces have been killed off. There are two different types of solution that can be used both having different advantages and disadvantages.

2. Bleach/water mix solution.

Sodium hypochlorite mixed with water to create a bleach solution is very effective at killing any remaining lichen spores. It works very quickly within a few minutes of application. One application after pressure cleaning will ensure that all remaining lichen spores are dead and will prevent fast regrowth. However it can also be applied before pressure cleaning as well which can make the process of pressure washing much faster and easier. Bleach solutions containing sodium hypochlorite are hazardous to health so should be handled with care and personal protective equipment should be worn. Safety equipment such as goggles, chemical resistant gloves and a facemask are essential as contact with the skin can cause burns. Any splashes on clothes will quickly bleach out colours. Noxious fumes can also be released so use of a respiritary mask with a safety rating of N95 must be worn. Surrounding plants and lawns should be watered thoroughly before and during the application. A solution of 3 to 3.5% sodium hypochlorite will kill white spot lichen. Stubborn lichen spots should be agitated with a stiff brush and then a repaeat application made until they dissapear.

3. Biocide solution containing DDAC

A biocide solution can be used in two ways, firstly it can be applied after pressure cleaning to kill any remaining traces of lichen. It can also be applied alone without pressure cleaning first. This is a quick and easy method of treating lichen but requires patience as lichen will die off slowly over a few weeks. It has an advantage over bleach as it will prevent regrowth, however unlike a bleach solution this will not have instant results. Heavily invested driveways are likely to require repeat applications to completely eliminate the white spots. Applied once a year will prevent regrowth of lichen.

Can you stop lichen from growing on a driveway?

Application of a biocide such as BAC-50 will not only kill lichen it will also prevent regrowth for several months. Applied once every 12 months in drier climates or every 6 months in climates with regular rainfall, preferably in warm, dry weather will prevent lichen from being able to grow on your driveway.

Professional Driveway Cleaning and Lichen Removal Service

We provide complete driveway cleaning and white spot removal service covering Birmingham, Sandwell, Solihull, Sutton Coldfield and surrounding areas. Contact us on 0121 296 0215 to arrange a free, no obligation quotation.