Flagstone is a beautiful addition to any outdoor space, but over time it might feel like it's a fight of flagstone against nature. It can become grimy with moss, grease stains, rust stains, and just a general buildup of dirt. Thankfully, pressure washing is an easy cleaning process to bring back the beauty of the natural stone surfaces.
Important Notes
- If your stones have a flagstone sealant, make sure it is suitable to pressure-wash.
- Avoid vinegar, bleach, or harsh cleaners because they can discolor the flagstone over time with acid stains.
- Pressure washers have. To safely clean your entire patio, choose a nozzle with a larger angle tip. A zero-to-15-degree tip will be too powerful and may pit or flake your stone. A 25-degree tip held at a 45-degree angle is safer. Always test an inconspicuous area first!
8 Steps to Pressure Washing Flagstone
- Prepare the Area. Remove any furniture or obstacles from the zone you'll be pressure washing. Sweep away loose debris. Wet the surface with water to soften pollen and dirt.
- Choose your nozzle and test the Pressure Washer. Pressure washers can be fit with various tips—from a very fine jet stream (zero-degree) to a wider fan spray (~45-degree). We recommend something close to 25-degrees, which is powerful enough to lift moss, but gentle enough to prevent damage. Test the pressure washer on a small, inconspicuous section. Flagstone can have a particularly delicate nature, but you will be okay if you adjust the tip and pressure settings to get even results.
- Apply Detergent. If your flagstone faces heavy foot traffic it likely has stubborn stains. Applying a detergent specifically formulated for pressure washing. Allow this mild cleaning solution to sit for a few minutes on stubborn dirt and tough stains (you can check with a stiff brush to see if it's made headway before washing it all away too early).
- Begin Pressure Washing. Starting from one corner, use smooth, overlapping strokes of cold water to pressure wash the flagstone surface. Hold the nozzle at a consistent distance and angle from the stone (around 45-degrees) to ensure even cleaning. Work systematically to cover the entire area. Don't hover, just go back over mildew spots.
- Pay Attention to Joints and Crevices. Moss and dirt tend to accumulate in the joints and crevices between stones. You may need to pay extra attention to these areas. Be aware that chunks of loose dirt or chips of stone may come loose if you aren't careful.
- Rinse Thoroughly. Once you've cleaned the entire flagstone surface, switch to a clean water nozzle attachment to rinse away any remaining detergent. Ensure all areas are thoroughly rinsed.
- Repeat if Necessary. Apply detergent and go back over deep-seated stains.
- Allow to Dry. After pressure washing, allow the flagstone to air dry completely before replacing any furniture or using the area. This prevents slips and falls on wet surfaces and allows you to fully appreciate the results of your hard work.
How often does flagstone need to be cleaned?
It depends on the climate, but assume regular cleaning twice a year. Surprisingly a well-trekked flagstone patio might need just as much care to combat dirt as a lesser used flagstone walkway might need to combat moss.
Can you pressure wash stacked flagstone walls?
Yes, you can pressure wash stacked flagstone walls using the same techniques outlined above. Be careful because you can inadvertently dislodge loose stones or cause damage to the mortar. If working over a garden bed, use an eco-friendly detergent, and cover delicate plants with a sheet or light tarp.
Are there any alternatives that effectively clean flagstone?
An alternative cleaning solution would be to rub the flagstone pavers with a stiff scrub brush, warm water, and dish soap/mild detergent (avoid harsh chemicals). Rinse with clean water or a garden hose and let dry. This is a good technique if you want to target tough stains, but it will take more time and effort than pressure washing.
