lichen removal

The unsightly black spots that emerge on patios and driveway are what is known as lichen. Lichen are a combination of fungus and algae, or cyanobacteria. And similar to fungi, lichen need a carbon food source.

Lichen prefer porous natural stone such as Indian Sandstone because they feed on the minerals within the stone, although materials such as block paving and concrete slabs are not immune. They have roots that are known as hyphae, which form a ‘crustose’ growth and penetrate the surface which make them very difficult to remove.

Very little will remove lichen from paving, high power pressure washing has little effect and sand blasting will just serve to damage the surface of your driveway or patio. Also many ‘off the shelf’ remedy’s do not work.

As we have come across this problem may times we have developed a tried and tested procedure to remove lichen without damaging your paved areas.

Below are examples of an Indian Sandstone patio before lichen treatment.

lichen patio
lichen patio
And an example of the same area once the lichen has been treated.

lichen patio

Sealing a driveway or patio

A question that we commonly get asked is “should I seal my driveway or patio”, so we have put together some information on block paving sealants, the benefits, and when to use them.

The main types of sealant are:

◾Moisture cured urethanes.

◾Water based emulsions.

◾Solvent based acrylics.

◾Hydrated Polymer glues.

Sealants originally emerged in the printed concrete market as a crucial element of the finished project, but more recently have been used in the concrete block paving market as stain preventers, weed preventers, to aid structural integrity and as colour enhancers.

The most commonly used sealants are acrylics and urethanes(polyurethane), and although both can be used for residential block paving the acrylic sealants are the most frequently used in this situation.

Acrylic sealants are most effective in enhancing the colour and to give it an all year round “wet look”, they’re cheaper to buy but are not as durable or flexible as the more expensive urethane products. Acrylic sealants could be affected by oil or petrol and commonly need re-application. Acrylic sealants are suitable for your block paved drive or patio but have limited effectiveness in comparison with more expensive products.

Polyurethane based sealants are better at protecting your paving against petrol and other hydrocarbons. This type of sealant is mostly used on commercial projects and offers structural integrity in the sand joints. It prevents staining, efflorescence and offers better protection against weed growth.

So the choice of which to use will come down to a matter of cost and the individual project in hand, as some sealants may be more suitable than others in different circumstances.