If you've got block paving, a sandstone patio or a concrete driveway, the question of sealed vs unsealed paving comes up sooner or later — usually when you're standing outside wondering why it looks worse every year despite the occasional hosing down. The difference between a sealed and unsealed surface isn't just cosmetic. It affects how quickly algae takes hold, how deep staining gets, how often the surface needs professional attention, and what it costs to restore when things have been left too long.
Greater Manchester's climate doesn't help. Oldham, Rochdale and the surrounding towns sit in one of the wetter parts of England, with persistent low cloud, limited drying sun between October and April, and enough freeze-thaw cycles each winter to work against mortar, jointing sand and surface sealants alike. Whether your paving is sealed or unsealed shapes how it weathers all of that — and understanding the difference helps you make better decisions about maintenance, rather than discovering the hard way that you've left things too long.
After a deep clean and re-sand, sealing is an option — but only once the surface is properly prepared.
Quick answer: Sealed paving repels stains, resists moss and weed growth, and needs less frequent deep cleaning — typically every 2–3 years. Unsealed paving is more porous, stains faster, and usually needs professional cleaning annually. The right approach depends on your surface type, usage, and whether it's been properly cleaned before sealing.
What Does 'Sealed' Actually Mean?
A paving sealant creates a barrier between the surface of the material and everything trying to get into it — water, oil, algae spores, organic debris. What that barrier looks like depends on the type of sealant used. Impregnating sealers, sometimes called penetrating sealers, soak into the pores of the paving and line them from the inside without changing the surface appearance significantly. They repel water and oil at a molecular level while letting the material breathe. These tend to be the better choice for natural stone and porous concrete block paving.
Topical or film-forming sealers sit on top of the surface rather than inside it. They create a visible coating — often with a wet-look or satin finish — that physically covers the paving. These are more obvious in appearance and, when they start to break down, they can peel, cloud or trap moisture beneath them. The finish can look good on block paving when applied correctly, but the prep work has to be right or you end up with problems that are harder to fix than unsealed paving ever was.
Neither type lasts indefinitely. Both require the surface to be properly cleaned, dry and structurally sound before application. That last point matters more than most people realise.
How Unsealed Paving Behaves Over Time
Untreated block paving, sandstone, concrete and similar surfaces are porous by nature. In a wet climate like Greater Manchester's, that porosity is the main reason surfaces degrade faster than people expect. Rainwater carries algae spores, fine organic particles and airborne debris into the surface. Once algae establishes itself — typically starting in sheltered or shaded spots — it holds moisture against the paving, which accelerates the cycle. What starts as a faint green tinge becomes slippery black growth fairly quickly, particularly through autumn and winter. You can read more about what actually clears it in the guide to what actually removes algae from paving.
Jointing sand is another casualty. On unsealed block paving, the sand between joints erodes through foot traffic, vehicle weight and heavy rainfall washing it out. Once the joints thin down, weeds establish easily and the blocks themselves lose lateral stability. Staining from oil, rust or organic matter on an unsealed surface doesn't stay near the top — it migrates into the material, which is why some stains on untreated sandstone or concrete never fully lift even with professional treatment. Honest answer: some lighten rather than vanish completely.
None of this means unsealed paving is a mistake. It's the default state of most paving, and plenty of it stays perfectly serviceable with the right maintenance. It just requires more regular attention to stay that way.
How Sealed Paving Behaves Over Time
A quality seal applied to properly prepared paving does make a genuine difference. Algae and moss establish more slowly because there's less porosity for spores to anchor into. Staining from oil or organic matter sits on top of the sealant rather than penetrating the material, which makes it easier to clean off before it becomes a problem. The jointing sand is also better protected, particularly if kiln-dried sand was compacted into the joints before sealing. For block paving on a busy driveway, that combination of joint stability and surface protection makes a meaningful difference over two or three years.
The limitations are worth being clear about. Sealant degrades. UV exposure, vehicle traffic, freeze-thaw cycles and general weathering all break it down. In the North West, where a surface might sit wet and shaded for months at a time, that degradation can happen faster than the manufacturer's figures suggest. A topical sealer that starts to fail can trap moisture between itself and the paving underneath, causing the sealant to blister, peel or go milky — at which point it looks worse than an unsealed surface would have. An impregnating sealer fails more gracefully, but it still needs reapplying on a realistic schedule.
Sealed paving is also not maintenance-free. It still needs periodic cleaning. What it gives you is more time between those cleans, and usually a faster, less intensive clean when the time comes.
Cleaning Frequency: Sealed vs Unsealed Side by Side
For unsealed block paving or a patio in a typical Greater Manchester garden — partial shade, some tree coverage, regular foot or vehicle traffic — a professional clean every one to two years is a reasonable working expectation. Leave it to three years and you're usually looking at heavier moss, compacted organic matter in the joints, and potentially some staining that has worked deeper into the material. The block paving cleaning process itself is more intensive and takes longer, which is reflected in the cost. Basic cleaning starts from around £3.50 per square metre; surfaces that need chemical treatment for algae or moss come in from £4.25 per square metre.
Sealed paving, assuming the sealant is still intact and was applied over a properly cleaned surface, can realistically go two to three years between professional deep cleans. Some patios with good sun exposure and less tree canopy go longer. The key variable is whether the sealant is still doing its job — if it's visibly breaking down, the surface starts behaving like unsealed paving again and the maintenance interval shortens accordingly.
Tree coverage is the single biggest factor affecting how quickly any paving — sealed or not — deteriorates in Greater Manchester. Leaf tannin staining, constant moisture from dripping canopy and shade that prevents drying all accelerate algae and moss growth significantly. If your paving sits under or near trees, budget for more frequent attention regardless of whether it's sealed.
The One Thing That Ruins Both: Skipping Preparation
Sealing over paving that hasn't been properly cleaned and re-sanded is one of the most common mistakes, and it causes more problems than simply leaving the surface unsealed. If algae or moss is present when sealant goes down, you've locked biological growth underneath a coating that prevents it from drying out or being treated. The sealant peels from below as the organic matter continues to break down, and you're left with a surface that's harder to restore than if it had never been sealed.
The same applies to jointing sand. Sealing block paving with degraded or absent joint sand doesn't stabilise the surface — it just coats it. Blocks continue to shift, the sealant cracks along the joint lines, and water gets underneath through those cracks. A full restoration — block paving re-sanding after a thorough clean — always needs to happen before any sealant goes down. Re-sanding alone on a cleaned surface runs from around £2.00 per square metre; a full restoration with clean, treatment, re-sand and seal runs from £5.50 per square metre.
The honest summary is that preparation is most of the work. The sealant is the last step, not the first solution.
When to Call a Professional Rather Than DIY
Consumer pressure washers — the kind you'd pick up from a DIY shed — typically run at 100 to 130 bar. Most professional equipment runs at 200 bar or above with higher flow rates, and more importantly, operators know the right pressure for the material they're cleaning. Using too much pressure on sandstone or tumbled block paving damages the surface face. Using too little on a heavily contaminated concrete drive barely touches the problem. If your paving has deep black spot staining, compacted moss that's physically rooting into the joint sand, or a sealant that has clouded and peeled, a consumer machine won't resolve it. You can find more on that in the guide on how to clean a mossy driveway safely.
There are also situations where chemical treatment is the right tool rather than pressure alone — particularly for organic growth on render, roofing or natural stone, where a biocide applied with dwell time does more work than mechanical force ever could. That's the basis of softwashing, which uses sodium hypochlorite at controlled dilutions to kill algae and moss at the root rather than just disturbing the surface layer.
C&C Precision Pressure Washing cover all of Greater Manchester — Oldham, Rochdale, Bury, Tameside, Bolton, Stockport, Manchester city and surrounding towns. Quotes are straightforward: send photos over WhatsApp and you'll get a realistic price back, usually the same day. There's no obligation and no pressure.
Practical Takeaway: Which Route Is Right for Your Paving?
Unsealed paving costs less upfront and is the natural state of most surfaces. The trade-off is higher maintenance frequency — roughly annual to biennial professional attention to stay on top of algae, moss and joint degradation. If you're disciplined about that, unsealed paving holds up well and never presents the risk of sealant failure. It's a reasonable choice for lower-use areas or anyone who prefers straightforward ongoing maintenance to a larger periodic outlay.
Sealed paving done correctly — over a properly cleaned, re-sanded, fully dried surface — genuinely reduces the effort and frequency of maintenance. It's the better long-term investment for a busy driveway or a patio you use regularly and want to keep looking good with minimal intervention. The higher upfront cost reflects the preparation work, not just the sealant itself. The decision on sealed vs unsealed paving often comes down to that trade-off: lower initial cost with more regular maintenance, or higher initial cost with less frequent attention needed.
If your paving is already in a bad state, the sequence is always the same regardless of which route you're taking going forward: clean thoroughly, re-sand if the joints need it, let the surface dry fully, then seal if that's the direction you've chosen. Trying to shortcut any of those steps produces worse results than starting from scratch would have.
Frequently asked questions
Does sealing block paving stop weeds and moss completely?
No — it significantly reduces growth by limiting the moisture and organic material that weeds and moss need to establish, but it won't eliminate them entirely, especially in joints. Kiln-dried sand compacted into the joints after cleaning does as much work as the sealant itself. You'll still want to check the surface each season.
Can I seal my paving straight after pressure washing it?
Not immediately — the surface needs to dry out fully, which in a Greater Manchester climate can take several days of dry weather. Sealing damp paving traps moisture underneath and causes the sealant to cloud, peel or blister. A reputable contractor will always factor drying time into the job.
Is unsealed paving harder to clean than sealed paving?
Generally yes — unsealed surfaces are more porous so algae, oil and organic matter penetrate deeper into the material rather than sitting on top. That means more dwell time with appropriate treatments and higher pressure to lift stubborn staining. Sealed surfaces, if the sealant is still intact, tend to clean up faster and with less effort.
How long does block paving sealant last in the UK climate?
Most quality sealants last between 3 and 5 years on a driveway that gets regular vehicle traffic, and longer on patios or paths with lighter foot traffic. The Greater Manchester climate — frequent rain, limited drying sun — does accelerate UV and freeze-thaw degradation compared to southern England. Getting the surface professionally cleaned and re-sanded before resealing extends the life of each application.
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