exterior
Patio and decking cleaning
Cleaning a patio costs £150 to £350 for a typical garden, or £3 to £6 a square metre. Most of what makes a patio look dirty is algae, which washes off easily, and the black spots that stay behind afterwards are lichen, which does not: that needs a chemical treatment and a fortnight, not more pressure.
What this covers
What it costs. Patio cleaning costs £150 to £350 for a typical garden, or £3 to £6 a square metre. Full cost breakdown.
What the job covers
- Patios in stone, concrete slab, porcelain or block paving
- Algae and black spot lichen, which need chemical treatment rather than pressure
- Decking, cleaned at low pressure and re-oiled where wanted
- Re-pointing or re-sanding joints after the clean
- Sealing, where the surface takes it and the owner wants it
What is involved
The black spots are the thing worth understanding before booking. They are lichen, they bond to the stone rather than sitting on it, and no amount of pressure removes them without taking the surface with them. A treatment is applied, left for one to three weeks, and the spots fade and go. A firm that promises to blast them off in an afternoon is promising to damage the slab.
Surfaces differ more than they look. Concrete slabs and porcelain are robust. Indian sandstone is soft and pits under a turbo nozzle. Limestone and travertine are softer again and should be cleaned chemically at low pressure. Block paving needs re-sanding afterwards.
The joints are the part people forget. A cleaned patio with washed-out pointing looks worse than it did and lets water under the slabs, so re-pointing or re-sanding belongs in the quote rather than in a phone call two weeks later.
Choosing someone for the job
Ask what they will do about black spot, and treat any answer that involves pressure as a reason to call somebody else.
Ask what the patio is made of and whether they have cleaned it before. Sandstone, porcelain, concrete and limestone want four different approaches.
Ask whether the joints are made good afterwards, and get it on the quote either way.
Common questions
Why are the black spots still there?
They are lichen rather than dirt. Lichen bonds into the stone and comes out with a treatment over one to three weeks, not with a pressure washer.
Will cleaning damage my slabs?
It can. Sandstone, limestone and travertine are soft enough to pit under a narrow nozzle held close. Concrete and porcelain take pressure comfortably.