How do I remove black spot from my patio?

Removing black marks from your patio can be quite difficult and time-consuming if you don’t reach for the right black spot remover. But don’t worry, Stoneworld got you covered. In this post, we will discuss which black spot remover for patio is the right choice to save your stone surfaces as well as present other alternatives to clean your patio.   

What is black spot?

Black spot is lichen which thrives on stone surfaces in the damp and shady conditions that are so common in the UK. The characteristics of the lichen are that as it matures, it sends out tendrils (hyphae) into the pores of the stone seeking nutrients from the minerals in the stone and the detritus that collects on the patio. These gradually spread through the surface of the affected stone.

An example can be seen here on a recent customer’s sandstone patio:

And here on a granite patio last year:

What is the most effective way of removing black spot from my patio?

A far more effective method of killing and removing black spot, is to use a black spot remover for patio like Rob Parker’s Best Patio Cleaner. The product has been developed with chemists after researching the best way to kill the lichen to prevent new growth, and also remove the existing marks.

Our black spot remover for patio is effective in removing black spots and our customers are very satisfied. Rob Parker’s Best is a biocide which will get into the growth and kill the black spot permanently, but also has a bleaching agent which will bleach the blackness out of the visible black spot.

In order to work properly it is necessary to ensure that the Rob Parker’s Best Patio Cleaner – a black spot remover for patio – remains on the affected stone for at least an hour, and that during the treatment period the stone surface remains wet. The black spot remover can be used on all types of stone such as patios, driveways, and paths. 

Sometimes, particularly stubborn deposits will remain on the stone after treatment.

Over time, now that there is no live lichen in the stone, these (bleached) dead deposits will loosen, and the next time the patio is power washed, any remaining lichen deposits will be removed and the stone surface will become as clean and brilliant as it was when first laid.

Which stones are most affected by black spot?

As black spot causes problems by getting into pores, it is a bigger problem on stones that have larger pores as part of their structure.

Stones that are often worse affected by black spot:

Stones that are not as badly affected:

However, there is a hierarchy within the Indian Sandstones, whereby some colours are more affected than others. For instance, the better quality Raj Green is one of the densest, close textured sandstones available, and therefore, because of its structure, will not be affected.

However, as you move through the colour range of the Indian sandstones from dark to light, the occurrence of black spot becomes more prevalent:

Will pressure washing remove black spot from my patio?

During the first 2 years after a stone surface has been laid, any black spot growth will appear to be simply a surface problem that can be successfully removed by power washing. This is not removing or killing the spreading hyphae that are within the stone surface, however.

Over an extended period the hyphae, now well established within the stone surface, create an anchor for the black spot to colonise the stone surface which will become increasingly blackened, and more difficult to clean away.

If pressure washing is not effective, what other options are there for removing black spot from my patio?

The use of a high temperature, low pressure steam cleaner (such as Doff) will kill the black spot but unfortunately will not always remove the more stubborn black marks on the stone.

If you have any questions or would like to talk to one of our team, please call us on 01844 279274 or email us at sales@stoneworld.co.uk and we will be happy to help you.

Last updated: 16/08/2024