What to Know Before You Pressure Wash Flagstone

A beautiful small, urban backyard garden featuring a tumbled paver patio, flagstone steps, and a variety of trees, shrubs and perennials.

Flagstone patios can add style to your outdoor areas without all the upkeep requirements of a wooden deck. However, just because flagstone needs less maintenance doesn’t mean they are 100% maintenance-free. Pressure washing is an effective way to make your flagstone patio the envy of your neighbours.

The Grounds Guys are familiar with working with materials like flagstone, and we’re fully equipped to thoroughly clean any flagstone surface without damaging it.

What Is Flagstone?

Flagstone is a sedimentary rock that usually comes in reds, blues, and grays. It’s cut into a square or rectangular shape to be used as a building material for walls or patios. Because flagstone is naturally occurring, not a poured concrete paver, extreme or harsh power washing can worsen natural impurities, leading to an unpolished appearance. Knowing how to clean your flagstone correctly will keep your patio fresh-looking and damage-free.

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How to Clean Flagstone Pavers and Patios

Before cleaning your flagstone, you’ll need to consider what substance you’re cleaning off the surface. Although many common causes of tarnished flagstones can be addressed with power washing, it’s not always the best solution. Natural wood, cement siding, concrete slab, and garbage cans are materials ideal for pressure washing.

Can I Pressure Wash a Flagstone Patio?

While you can pressure wash a flagstone patio, you’ll want to use the proper process, tools, and cleaning solution for optimal results. Use low pressure to avoid damaging your flagstone, and make sure you or your contractor is using hot water.

How to clean mortar haze off flagstone:

To remove mortar haze and residue, begin by using a scraper or chisel to get as much off as possible. Then, use a hose or bucket to wet down the patio area. Pour a non-acidic cleaner over any residue you couldn’t get off with the scraper. After the solution begins to bubble and dissolve the residue, use a stiff bristle brush or another coarse tool to remove the residue. Repeat this process until you’re satisfied; then finish by running a hose or pressure washer to rinse any leftover residue and cleaner off your stone.

How to clean mildew from a flagstone patio:

Mould and mildew growth on your patio should be addressed as soon as it’s identified. One of the best tools to combat mildew is vinegar, which you probably already have in your home. Using a spray bottle or pouring method, apply full-strength vinegar or a water and vinegar blend directly to any mildew spots. Let the vinegar or solution sit for approximately 15 minutes before washing it off with a hose or pressure washer.

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How to Avoid Damaging Your Flagstone

If you’re cleaning your flagstone, you’re probably trying to restore it to its ideal condition—damaging the surface is not what you have in mind. Fortunately, there are steps you can take to make the flagstone squeaky clean while leaving it perfectly intact.

Follow these tips to avoid damage as you clean your patio:

  • Keep your pressure washer nozzle a safe distance from the stone. Your pressure washer’s stream is most powerful at the tip of the nozzle. If the tip is too close to the stone, you can chip and crack it.
  • Don’t use a water stream that is too forceful. Flagstone, like any stone, will erode with prolonged exposure to running water. If you use a too high pressure setting while cleaning, you can remove layers of the stone or create unsightly cracks and chips.
  • Avoid acidic cleaners. Although acidic cleaners will remove mildew and mould from flagstone, it’s important to remember that acids can lead to stains if left on the surface too long. Acid-based cleaners are also dangerous to humans and animals and can kill plants or other flora surrounding your patio.
  • Don’t let water remain too long on the stone. Whether you use a hose or pressure washer, avoid letting water sit on the stone too long. Flagstone will naturally crack, and the pooling water can increase the likelihood that moisture will get inside cracks and create mould growth.

Find a Power Washing Service Professional Near You

The best way to clean flagstone without causing damage is to leave this pressure washing task to the pros at The Grounds Guys. Our team of experienced local service professionals are here to help get your patio and the rest of your landscaping looking like the day it was installed. Give us a call or request a job estimate online for the landscaping and pressure washing services you can trust.