How to remove black spots from patio

Question

I have got persistent black spots all over our patio slabs. I've tried brushing and pressure washing but they keep coming back? What are they and how do you actually get rid of them

Damon · Accepted Answer

Those black spots are usually lichen or black spot algae, and pressure washing alone won’t fully remove them — it just takes the surface off, so they come back.

The proper way is to use a patio biocide to kill the growth inside the stone, leave it to work for 24–48 hours, then lightly clean it off. For longer results, sealing the patio afterwards helps stop it returning.

So basically: kill it first (chemical treatment), then clean — not just jet wash 👍

Michael · Answer

The persistent black spots are lichen, a slow-growing plant organism. Lichen creates deep, tiny roots that wedge inside the stone. Pressure washing only removes the surface growth. It leaves the hidden roots behind, allowing the lichen to quickly grow back

Nathan · Answer

Its is called lichen its a crusty living patch of fungus or algae, it is almost impossible to remove.  Although by using some chemical patio agents and leaving in on the affected areas for 24 hours, the longer the better. You can remove or reduce some of it. Alternatively you can yluse a brick acid, but the will eat away at the face of the paving slab and I would not recommend thus action.

Pete · Answer

Hi try white vinegar or 1 part bleach 5 part water always worked for me Black spots on a patio are often caused by stubborn algae, lichen, or a type of black mold. They’re much harder to remove than ordinary dirt

Ryan · Answer

try a solution called patio clear ive used it several times also work well on green mildew on fences

Harley · Answer

You should put plenty of patio cleaner down let it soak in scrub and pressure wash and keep on top of cleaning

Joe · Answer

Could try using brick acid plus the power washer to fully get rid of the spots

Martyn · Answer

This is stubborn black lichen.. It sits in the pores of the slabs you need to pressure wash with sodium hypochlorite

Marc · Answer

Go online and look for black spot remover . I take it you have Indian sandstone slabs. It’s normal for black spots to appear as they are a natural stone materials. Has the slabs been sealed before ?

James · Answer

Strong cleaner like sodium hypochlorite and a pressure wash would solve this.

How to remove black spots from patio

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