Why pavers turn green in the monsoon
Moss and algae grow where paving stays wet and gets little sun: under trees, beside walls and in corners where water collects. Months of rain give them ideal conditions. Weeds grow from seeds that land in joints that have lost their sand. Green paving is not only untidy; it is slippery, especially on steps and slopes.
What to use for each problem
| Problem | What it looks like | What to do |
|---|---|---|
| Algae | Green or black slimy film, slippery when wet | Scrub with a stiff brush, water and mild detergent; rinse |
| Moss | Soft green clumps, mostly in joints and shady spots | Scrape out of the joints, scrub, rinse and re-sand |
| Weeds | Plants growing up through the joints | Pull out with the roots, then refill the joints with sand |
| Efflorescence | White powdery patches, mostly on new pavers | Brush off when dry; it fades with time and rain |
| Mud and leaf stains | Brown marks after heavy rain | Sweep, then wash with water and mild detergent |
How to clean pavers after the monsoon
- Sweep. Brush off leaves, mud and loose dirt with a stiff broom.
- Clear the joints. Pull out weeds with their roots and scrape moss out of the gaps with a thin tool.
- Scrub. Wet the surface and scrub with a stiff brush and water with a little mild detergent.
- Treat stubborn growth. If green patches remain, use a cleaner made for paving. Test it on a hidden corner first, because strong chemicals such as bleach or acid can mark coloured pavers and harm plants beside the paving.
- Rinse. Rinse with clean water. If you use a pressure washer, keep the jet at a low angle so it does not blow the sand out of the joints.
- Re-sand the joints. When the surface is dry, sweep joint sand into the gaps until they are full, and pack it down.
Why re-sanding matters
The sand in the joints is what locks pavers together. When rain and cleaning wash it out, pavers can move, rock and become uneven, and weeds take the empty space. Refilling the joints after cleaning keeps the surface firm and leaves nowhere for weeds to grow.
How to stop it coming back
- Fix spots where water pools: paving needs a slope so rain runs off.
- Trim back trees and plants that keep paving in shade and drop leaves on it.
- Sweep regularly, so leaves and soil do not sit on the paving and feed growth.
- Keep the joints full of sand.
- Consider a sealer after cleaning; it makes the surface easier to clean.
For grass pavers, the grass is meant to grow: mow and water it instead. See the grass pavers guide.
A simple yearly routine
| When | What to do |
|---|---|
| Before the monsoon | Clear drains and gutters near the paving, check the joints are full, and trim overhanging plants. |
| During the monsoon | Sweep off leaves and mud, and watch for water that does not drain away. |
| After the monsoon | Remove moss, algae and weeds, clean the surface, and re-sand the joints. |
Sri Lanka has two monsoons. Follow the routine around the one that brings your area its heaviest rain, and check the paving after the other as well.
Frequently asked questions
How do you remove moss and algae from pavers?
Sweep off loose dirt, wet the area, scrub with a stiff brush and a mild detergent, and rinse. For stubborn growth, use a cleaner made for paving, tested first on a hidden corner. Then let more sun and air reach the area so it does not come back.
Can I pressure wash pavers?
Yes, carefully. Keep the nozzle at a low angle and not too close, because a strong jet blasts the sand out of the joints. Refill the joints with sand afterwards.
What is the white powder on new pavers?
It is usually efflorescence: natural salts that come to the surface of concrete products as they dry. It is not a defect, and it fades with time and rain. Brushing it off dry helps; avoid washing it with acid.
How do you stop weeds growing between pavers?
Pull the weeds out with their roots, brush the joints clean, and refill them with joint sand, packed down to the top. Full joints leave no room for seeds to grow.
Need help with old or damaged paving?
If your paving has sunk, cracked or lost its joints, we offer a free site inspection and can quote for restoring it or replacing the damaged area.
Browse our pavers range or request a free consultation.