When the sun is out and stone or block paving is dry, driveways and patios look their best.
However, in parts of the world that face colder periods, elements such as rain, frost and shorter days with less sunlight all put increased pressure on block paving and natural stone. These can causes real issues if they do not have protection from sealing.
If you’ve noticed your paving:
- Looking green or discoloured
- Feeling slippery
- Paving slabs starting to shift or move
These are often signs that the surface requires some immediate help.
Algae: the hidden slip hazard
Damp, shaded conditions are ideal for algae, moss and lichen. Unsealed paving is porous, so it holds moisture close to the surface for longer. This gives organic growth the foothold it needs, and one that can become dangerously slick.
Slips and trips are one of the most common causes of injury in the UK, both at home and at work. For homeowners, a green, greasy patio or path can be a real risk for children and older relatives, especially if covered by fallen wet leaves. For businesses, schools and commercial sites, it can also become a liability issue.
Sealing reduces the porosity of the surface, which means water sits on top and runs off rather than soaking in. With less trapped moisture, algae struggles to establish itself and any growth that does appear is far easier to clean away.
While paving sealer is a good long term solution for this, it may not be viable given the time of year (discussed below). We also provide Resiblock Algae, Mould and Lichen Remover to help with removing this more quickly it is an immediate issue.
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Loose jointing sand and moving pavers
The sand between block paving does more than fill gaps. It locks the paving together, spreading load across the surface and stopping individual blocks from moving. Over the autumn and winter, heavy rain can wash this sand out, pressure washing strips it away and freeze-thaw cycles can loosen it further.
Once the jointing sand goes, pavers can start to rock, sink or shift, particularly on uneven or sloping ground and on driveways where vehicles turn. Left alone, this leads to trip hazards, allows weeds to take root in open joints and, eventually, leads to the cost of relaying the paving.
A joint stabilising sealer such as Resiblock Superior binds the sand in place, so it stays put through the wettest months. The paving stays interlocked, weeds have a much harder time getting through and the surface keeps its shape.
Re-sanding block paving in the short term
In the short term, to resolve this issue with block paving you can add new kiln dried sand but before doing this you should:
- Remove weeds fully, roots included. A joint scraper or weeding knife works; a weedkiller first can help with stubborn roots. Anything left behind will regrow through the new sand.
- Clear the old joint material. Scrape out loose or contaminated sand and debris to a decent depth (ideally 15 to 20mm or more), otherwise the new sand just sits on top and blows or washes away.
- Let the paving dry completely. This is the step people skip. Kiln-dried sand won’t flow into damp joints and will clump on the surface.
- Brush in kiln-dried sand. Sweep it diagonally across the joints until they’re full.
We also advise compacting it. On block paving, you can run a plate compactor over it (with a rubber mat to avoid marking the blocks), then top up and repeat. Without compaction the sand can leave gaps.
Note: This applies to block paving and some flexibly laid paving. Most natural stone patios (Indian sandstone, limestone, slate) are laid with mortar or grout joints, and loose sand isn’t the right fix there. Those need re-pointing with mortar or a brush-in resin jointing compound.
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Why winter is the time to plan, not seal
Most paving sealers need dry conditions and temperatures above around 5°C to cure properly, so the depths of winter are rarely the right time to apply them. That doesn’t mean winter is wasted. It’s the best time to:
- Note where water pools or algae builds up in wetter periods and where sealing is most required
- Check for open joints and areas where sand has washed out
- Decide whether the surface needs immediate cleaning, re-sanding or repairs before sealing
- Build a budget and book any professional work early, before spring demand picks up
By doing the assessment now, you can clean, re-sand and then be ready to seal as soon as the weather allows in spring, giving your paving increased protection for the coming years.
Explore the Resiblock sealer range to find the right product for your surface, or find a Resiblock approved Contractor to get started.
Sealing Paving in Autumn and Winter FAQs
Why does paving get slippery in autumn and winter?
Paving becomes slippery in autumn and winter because damp, shaded conditions allow algae, moss and lichen to grow on the surface.
Unsealed paving is porous, so it holds moisture close to the surface for longer and gives organic growth a foothold, especially under fallen wet leaves. Slips and trips are among the most common causes of injury in the UK, and the Health and Safety Executive highlights wet and contaminated surfaces as a key risk.
Sealing reduces porosity so water runs off rather than soaking in, which makes it much harder for algae to establish. Resiblock sealers such as Resiblock Superior Natural Matt help keep surfaces cleaner and safer through the wetter months, and any growth that does appear is far easier to clean away. For existing growth, Resiblock Algae, Mould and Lichen Remover helps clear it more quickly.
Can I seal my paving in winter?
Winter is rarely the right time to seal paving, as most sealers need dry conditions and temperatures above around 5°C to cure properly.
Cold, damp weather can stop a sealer curing correctly, which affects how well it protects the surface. It’s worth checking the forecast with the Met Office and waiting for a dry spell in spring before applying any sealer.
Winter is the ideal time to assess your paving and plan ahead, so you’re ready to seal as soon as conditions allow. Resiblock’s how to apply guide explains the conditions and preparation needed for the best results.
How do I stop jointing sand washing out of block paving?
The most effective way to stop jointing sand washing out is to use a joint stabilising sealer, which binds the sand in place.
Heavy rain, pressure washing and freeze-thaw cycles all loosen jointing sand over autumn and winter, which can cause blocks to rock, sink or shift. The Interpave paving association provides further guidance on how jointing sand keeps block paving interlocked.
Resiblock Superior is a joint stabilising sealer that keeps sand in the joints through the wettest months, helping the paving stay interlocked and making it harder for weeds to grow through. It’s available in Natural Matt and Gloss finishes.
Should I re-sand the joints on my Indian sandstone patio?
No, most Indian sandstone patios are laid with mortar or grout joints, so loose sand isn’t the right fix.
Natural stone patios, including Indian sandstone, limestone and slate, usually need re-pointing with mortar or a brush-in resin jointing compound when joints fail. Re-sanding with kiln-dried sand is only suitable for block paving and some flexibly laid paving.
Once the joints are repaired, sealing helps protect natural stone from moisture, staining and algae. Resiblock offers an Indian Sandstone Sealer Invisible for a natural look and an Indian Sandstone Sealer Colour Enhancer to bring out the colour of the stone.
How should I prepare my paving for sealing in spring?
Use the winter months to assess your paving, so it can be cleaned, repaired and re-sanded before sealing in spring.
Note where water pools or algae builds up, check for open joints and decide whether the surface needs cleaning or repairs first. Booking any professional work early also helps you avoid the spring rush, and organisations such as TrustMark can help you find a vetted tradesperson.
When you’re ready, browse the Resiblock shop to find the right sealer for your surface. Resiblock’s technical data sheets provide full product details, so you can choose with confidence before the season begins.