Why is moss growing aggressively in my Vancouver paver joints?

Moss thrives in paver joints because Metro Vancouver's climate is essentially perfect for it — persistent moisture, mild temperatures, organic matter accumulating in joints, and often partial shade create ideal growing conditions.

The real question isn't why moss is growing, but rather what's making your joints particularly hospitable. Empty or eroded joints are the biggest culprit. When polymeric sand breaks down or washes out — which happens regularly in Vancouver's heavy rainfall — the open joint becomes a tiny planter: sheltered, moist, and filled with windblown organic debris like leaf fragments, pollen, and soil particles. Moss spores are everywhere in the Lower Mainland's air, and they colonise those open joints within a single wet season.

Shade dramatically accelerates the problem. North-facing patios, areas under tree canopies, and surfaces shaded by fences or buildings stay wet far longer after rain than sun-exposed areas. A south-facing patio in full sun might dry within hours of a rain event; a north-facing patio under a cedar tree might stay damp for days. That extended moisture window is exactly what moss needs to establish and spread. If your moss problem is concentrated on one side of your patio or along a shaded edge, this is almost certainly why.

Joint sand condition is the most important factor you can control. Healthy, fully intact polymeric sand leaves very little room for moss to root. The hardened sand surface is inhospitable compared to an open, debris-filled joint. If your joints look empty, crumbly, or if you can see gaps between pavers, replenishing the polymeric sand is your most effective long-term defence. In Metro Vancouver, plan to inspect and replenish polymeric sand every 3-5 years — more frequently on shaded or north-facing installations.

Treating Existing Moss

Don't pressure wash first — that spreads spores across the entire surface. Start by killing the moss before disturbing it. Iron sulphate (ferrous sulphate) is the most effective and commonly available moss killer in BC. Mix according to package directions and apply with a pump sprayer. The moss will turn black and die within 1-2 weeks. Zinc sulphate is an alternative that also provides some residual prevention. Avoid chlorine bleach — it damages polymeric sand, discolours pavers, and kills surrounding vegetation.

Once the moss is dead and dry, sweep or brush it off the surface. Then pressure wash at 1,500-2,500 PSI using a rotating surface cleaner attachment — this removes the dead material and cleans the joints without the striping pattern a wand creates. After the surface dries completely (give it 48 hours minimum without rain), sweep in fresh polymeric sand, compact it lightly, and activate with a controlled water application per the manufacturer's instructions.

Preventing Recurrence

Beyond joint sand, a penetrating paver sealer applied after the surface is clean and dry adds a layer of protection — it doesn't make pavers moss-proof, but it reduces the porosity of the paver surface, making it harder for spores to anchor. In heavily shaded areas, annual moss treatment in September (before the rainy season begins) keeps populations from establishing over winter.

If large trees are overhanging the area, keeping gutters clean and trimming canopy to allow more light and airflow makes a meaningful difference. You won't eliminate moss entirely in Metro Vancouver — it's part of living in this climate — but you can keep it manageable with annual maintenance rather than letting it take over.

Need help finding a hardscape professional to clean, re-sand, and seal your pavers? Vancouver Interlock can match you with an experienced local contractor for a free estimate.