Cleaning block paving properly: joints, weeds, stains and colour
Block paving is cleaned properly when the blocks come up clean and the joints keep as much of their sand as possible. That means a low jet angle, pressure matched to the paving, and a look at the joints once the dirt has gone, because open joints invite weeds back and let blocks move.
Send us a photo and the m²Why are the joints so important in block paving?
The joints are important because the sand in them locks the blocks together and spreads loads between them. Without it, blocks can shift, rock and sink at the edges.
Joints are also where dirt, seeds, moss and water collect. That makes them the first place to go green and the place where careless cleaning does the most damage.
A good clean therefore has two aims at once: remove what has grown or settled in the joints, and keep the jointing sand in place as far as possible.
How is block paving pressure washed without emptying the joints?
The jet is held at a low angle and moved along the joint lines rather than pointed straight down into them, at a distance and pressure that cleans the block faces without blasting out the sand.
- A test patch first, to see how loose the jointing material already is.
- Working in lines that follow the laying pattern.
- More care with herringbone and other patterns that have many short joints.
- Gentler settings on edges, kerbs and steps, where blocks are least supported.
Our block paving cleaning service describes how this works on drives, paths and stepped walkways, and the guide on how professional pressure washing works covers the general method.
What happens to weeds and moss in the joints?
Weeds and moss are removed along with the dirt in the top of the joints. Because their roots hold some of the sand, a little jointing material always comes out with them.
Cleaning does not stop new seeds landing. Joints that stay open and damp will host growth again, which is why the condition of the joints after cleaning matters more than the clean itself for how long the paving stays tidy.
If moss and algae are the main problem, see our rust, mould and moss service and the guide on rust, moss and black algae, which explains why shaded areas go green again faster.
When do joints need refilling after cleaning?
Joints need refilling when, after cleaning, the sand level sits clearly below the top of the blocks or gaps are visible along whole runs. Some loss is normal; large gaps are not something to leave.
| After cleaning you see | What it usually means |
|---|---|
| Sand just below the surface, joints tight | Normal; often no action needed |
| Visible gaps along several joints | Refilling is worth considering |
| Blocks that rock or move underfoot | Bedding problem; repair needed |
| Sunken areas or ruts | Base problem; a paving contractor should assess it |
Refilling joints and fixing minor edge damage can be part of the repair stage. Sunken areas and failing bases are outside cleaning and outside our work; we will say so if that is what we see.
How are stains on block paving treated?
Stains on block paving are treated the same way as on concrete: oil needs a treatment that draws it out of the pores, rust needs a treatment that acts on the iron oxide, and both are followed by a wash of the wider area.
The difference is that each block is a separate unit. A badly soaked block may stay darker than its neighbours even after treatment. Where that matters, individual stained blocks can be replaced by a paving contractor. The oil stain removal service explains what to expect from treatment.
What can owners do between professional cleans?
Between professional cleans, the most useful things are regular sweeping, keeping irrigation off the paving and dealing with spills before they soak in. None of these need special equipment.
- Sweep leaves, flowers and fruit off the paving before they stain or rot into the joints.
- Point sprinklers at the beds rather than the drive or the path.
- Wipe up oil, wine and barbecue grease while they are fresh.
- Pull the odd weed early, before its roots widen the joint.
- Keep metal furniture on pads so it does not leave rust rings.
For rental villas, adding these points to the gardener's or cleaner's routine keeps the paving presentable between visits. When you do book a professional clean, mention any spots that have been treated with something in the meantime, because residues can change how the surface reacts.
What if the blocks are faded rather than dirty?
If the blocks are faded rather than dirty, cleaning will make them clean but still pale. Colour that has bleached out of the concrete does not wash back in.
That is the point where some owners consider recolouring: clean, repair open joints and damaged edges, cut in by brush along walls and borders, then two coats of synthetic resin paint. Others prefer the natural look of clean, slightly faded blocks.
If you want to see what each route involves before choosing, read cleaning or recolouring, and compare with our general patio and driveway cleaning service.
Frequently asked questions
Will pressure washing ruin my block paving?
Not when it is done at the right angle and pressure. Careless washing with the jet aimed straight down can empty joints and scar block faces. A test patch and working along the joints keep the risk low. Edges and kerbs get extra care because they are least supported.
Why is sand coming out of my paving after cleaning?
Some jointing material always comes out, especially where weeds and moss were rooted. If the joints were already loose, more will come out. After cleaning, we look at the joints and tell you whether refilling is worth doing. Expect some sand in the runoff; that is normal.
Can cleaning stop weeds from growing between the blocks?
No. Cleaning removes existing weeds but does not prevent new seeds from landing. Well-filled joints and regular sweeping leave less room for growth than open, damp joints. Refilled joints and regular sweeping are the most effective ways to slow regrowth. Shaded, damp joints will always be the first to green over again.
Can stained individual blocks be cleaned?
Yes, usually with targeted treatment and a wash of the surrounding area. Heavily soaked blocks may stay slightly darker. Replacing individual blocks is a paving contractor's job, not ours. We tell you from close-up photos whether a block is likely to stay darker.
Why does my block paving look patchy after rain?
Patchiness after rain often shows differences in porosity, dirt or growth between areas. Damp, shaded parts stay darker for longer. A clean evens out the dirt-related differences but cannot change how the blocks absorb water. Blocks laid at different times can also weather differently.
Do herringbone patterns need special care?
Yes. Herringbone and similar patterns have many short joints in different directions, so there is more joint area exposed to the jet. The work follows the pattern carefully to limit sand loss. Edge blocks in these patterns are often the first to loosen.
Can block paving be painted after cleaning?
Yes, once it is clean, dry and sound. Recolouring block paving involves cleaning, joint and edge repairs, brush cut-in and two coats of synthetic resin paint. It changes the look of the paving, so it is a choice worth thinking through.
Is block paving harder to clean than imprinted concrete?
It is more delicate because of the joints. Imprinted concrete has no sand joints but often has a sealer that also needs care. Both need settings matched to the surface rather than maximum pressure. Natural stone needs even more care than either.
What does efflorescence look like on block paving?
Efflorescence shows as white deposits on the surface of blocks, often on newer paving. It comes from within the material. Some lifts with cleaning and some may reappear for a while. A close-up photo helps us judge. It is generally a cosmetic issue rather than dirt.
How do I know if my block paving needs more than cleaning?
If blocks rock, joints are wide open along whole rows, or areas have sunk, cleaning alone will not fix it. Those are repair or base problems. Photos of those spots help us tell you what kind of help you need.