Pressure washing is an effective way to cleaning large surfaces, as these incredibly powerful hoses can be super brilliant when it comes to removing dirt, dust, mud, grime, stains, salt, mold and even chewing gum from patios and driveways.
But there are certain things to look out for which is why you should understand what you’re dealing with before you begin to use one.
How pressure washing works
Firstly the pressure washer is a powerful piece of equipment designed to blast water at about 100–200 times the pressure of the air around us (that’s 1500–3000 pounds per square inch or psi). It uses a narrow, high-pressure jet of hot or cold water to blast dirt free from a surface.
The speed at which the water travels means it hits the outer layer of stone with high kinetic energy which knocks any dirt and debris away with little hammer-like blows. As you are using only water this shouldn’t damage your natural stone, however you may wish to run a test on a discreet area to make sure that it’s not going to have any undesirable effects.
The dangers of pressure washing
While pressure washing is effective when cleaning natural stone and other materials, there are reasons why you may want to be careful. Pressure washing can remove the natural patina of stone and also remove any coating or sealants. This can open up the pores and allow water to soak deep beneath the surface.
High pressure washing can saturate the stone and cause something called efflorescence. This is when salts from the stone that have dried out and appear as a white powdery substance on the surface. But you may not even see them as in many cases the salts will deposit into the pores of the stone and they’ll remain underneath the surface. If left undetected this may cause pitting, flaking and delamination.
You also have to be careful that you don’t damage the area between your natural stone slabs when using a pressure washer. The way to do this is to clean only the stone itself, avoiding the cemented part in between.
Can pressure washing harm my natural stone?
The colour will never wash out of natural stone, which might happen if you were cleaning a concrete or man-made patio but it is still advisable not to pressure wash too often.
Pressure washing checklist
While damage can be caused by pressure washing, if done properly, it is a great way to make your natural stone look as good as when it was first laid. With that in mind, you, or whoever will be doing the cleaning, needs to take a few steps to ensure it is done with care.
- The stone you are cleaning needs to be inspected to see how soft it is before you begin.
- The grouting between the stone also needs to be checked.
- You need to ensure the pressure you use isn’t above 1000 psi.
- Use only a fan tip. A zero fan tip should not be used.
- Do not use acids, bleach or high alkaline chemicals on your natural stone.
- Keep the pressure washer at least 12 inches away from the stone you’re cleaning.
Other ways of cleaning your natural stone
- The easiest way to clean your natural stone is to brush the surface regularly to remove anything that has the chance to leave stains
- In outdoor pool, patio, or hot tub areas, flush with clear water and use a mild bleach solution to remove algae or moss.
- Another effective way of cleaning your natural stone is to use a patio sealant. This will impregnate the stone and reduce any mould and algae build up developing on the surface of the slabs making cleaning much easier, and a simple case of hosing down the area and then scrubbing with a stiff brush.
How to clean your natural stone patio
Firstly remove all furniture, plants and ornaments from the surface and protect the lawn or flowers that may surround the area as the products you use are likely to kill them.
Secondly, mix your chosen cleaner with a bucket of hot water. This might be a cup of bleach, soda crystals or a prepared solution. Now you’re ready to begin.
- Hose down the patio to flush away debris to prime the surface.
- Scrub the area with a stiff brush using your cleaning solution.
- Leave the solution for five to ten minutes then rinse the surface with water. Again you may want to use a hose for this.
For more information on how to clean natural stone, follow our guide.
At The Premium Paving Company, we have broad range natural stone paving suitable for every project and budget. View our shop to take a closer look at our paving products. If you wish to know more about the different ways paving can be used in your garden, get in touch with our specialist team.