Slippery Green Slime: How to Kill Moss on Brick Pavers (And Keep It Gone)

The Scenario

You walk out the back door in January, coffee in hand, and nearly break your neck. That shady side of the house—the one the sun never hits—has turned into a skating rink. Your nice red brick patio is covered in a sheet of green moss, severely damaging its curb appeal. Dealing with these persistent moisture issues is common, especially when yard drainage problems are at play, but be careful not to trigger The Interlocking Friction Failure by blasting out the 'structural glue' between your bricks. It happens every winter—you scrub it, it comes back—and it feels like you’re fighting nature, and frankly, nature is winning.

"Any tips on how to get rid of this ???"

The GardenOwl Diagnosis

The Assessment

You walk out the back door in January, coffee in hand, and nearly break your neck. That shady side of the house—the one the sun never hits—has turned into a skating rink. Your nice red brick patio is covered in a sheet of green moss, severely damaging its curb appeal. Dealing with these persistent moisture issues is common, especially when yard drainage problems are contributing factors. It happens every winter. You scrub it, it comes back. It feels like you’re fighting nature, and frankly, nature is winning.

The Trap

The biggest mistake homeowners make here is grabbing the highest-powered pressure washer they can find and blasting the living daylights out of the patio.

Don't do that.

Yes, it removes the moss. But it also blasts out the sand between your bricks. That sand is the structural glue holding your patio together. Once you blow it out, the bricks start to wobble, water gets underneath them, and suddenly you have sunken spots and heaved edges. Plus, you haven't actually killed the moss spores; you've just moved them around. The brick itself is porous (it acts like a sponge), and without sunlight to dry it out, that moss will be back before you put the hose away.

The Solution (Deep Dive)

Since you can't move your house to get more sun on this spot, you have to change the surface conditions. Here is the step-by-step fix, ranging from "Annual Maintenance" to "Permanent Redesign."

Phase 1: The Kill and Scrub (Immediate Fix)

Before you worry about preventing it, you have to remove the slip hazard without destroying the patio base.

1. Chemical Warfare: You need to kill the spores, not just wash them off. Mix a solution of 30% bleach and 70% water (or use a dedicated product like Wet & Forget).
2. Soak and Sit: Spray the area liberally and let it sit for 15–20 minutes. You want the chemistry to do the heavy lifting.
3. The Manual Scrub: Use a stiff-bristle deck brush. Do not use a pressure washer unless it is on a very low setting. Scrubbing dislodges the dead moss without excavating the joints.
4. Rinse: Hose it down. The bricks should be red again.

Phase 2: The Lock-In (Maintenance)

Once the patio is dry—bone dry—you need to seal the gaps.

• Polymeric Sand: Sweep polymeric sand into the joints. This contains a binding agent that hardens like grout when misted with water. It seals the cracks so moisture can't sit in the crevices, and it makes it much harder for moss roots to grip the sides of the bricks.

Phase 3: The Design Swap (The Real Long-Term Fix)

If you are tired of doing Phase 1 and 2 every year, you need to accept that brick is the wrong material for this location.

Brick holds water. In deep shade, that water breeds moss. If you want a zero-maintenance floor in a damp, shady alley, rip out the pavers and replace them with 3/8-inch angular gravel or decomposed granite.

Why?

1. Drainage: Water flows through gravel instantly; it doesn't sit on top.
2. Movement: The surface shifts slightly when you walk on it. Moss needs a static surface to form that slippery sheet. It can't colonize loose stone.

If you hate the look of loose gravel, use large flagstone slabs with wide (3-4 inch) gravel joints. This minimizes the slick surface area and gives the water somewhere to go. For more on handling gravel areas, read about why weeds invade gravel and how to stop it.

Also, check your soil drainage. If water is pooling against the foundation, you might have a grading issue. The University of Minnesota Extension has good resources on understanding soil drainage, which is critical for these damp corners.

Visualizing the Result

Before you start ripping out bricks or ordering a truckload of gravel, you need to see if the new look fits your house style. You don't want to trade a mossy patio for a gravel pit that looks unfinished.

Use GardenDream to test the "Gravel Swap" concept. Upload a photo of your mossy side yard and overlay different materials—try slate chips, pea gravel, or flagstone. It’s a safety net that lets you see if the low-maintenance option actually looks good before you do the heavy lifting.

If you want to test this on your own yard, upload a photo of your yard to see what this design would look like using our Exterior Design App.