Should you seal a tarmac driveway? A Kent contractor’s answer
A properly built tarmac driveway should give you 20 to 25 years before it needs resurfacing. Most of what shortens that has nothing to do with the tarmac itself. Here is what actually matters, season by season, from a contractor that has been surfacing in Kent since 1979.
We surface roads, car parks and driveways, so we see the full range of how tarmac ages. The pattern is consistent. Surfaces that fail early almost always fail for one of two reasons. Water sat somewhere it should not have, or the construction underneath was never right in the first place. Very few fail because nobody polished them.
That is worth mentioning because a lot of driveway maintenance advice online is written by people selling sealant.
Our position on sealants and tarmac restorers
We do not seal tarmac driveways and we do not recommend it.
Sealants and so called tarmac restorers are cosmetic. They darken a faded surface for a while and they make it look wet and new in photographs. They do not add structural strength, they do not fix a soft or under specified sub base, and they do not stop a crack that is being driven by movement underneath. When they wear, they wear unevenly, which leaves a patchy finish that looks worse than the honest greying it was covering up. Some products also reduce grip when wet.
A tarmac surface that has gone slightly grey is not failing. That colour change is the bitumen at the very surface oxidising, and it is normal. If your driveway is grey but flat, sound and draining properly, it is fine. Leave it alone and spend the money on something that matters.
What does matter is everything below.
The seasonal maintenance table
| Season | What to do | Why it matters |
|---|---|---|
| Spring | Wash off winter grime with a hose and a stiff brush. Walk the whole surface and note any cracks that have opened over winter. Check the edges have not started to crumble. | Freeze and thaw does its damage between December and February, and spring is when you can see the result. Small cracks caught now stay small. |
| Summer | Treat moss and algae. Pull weeds at the edges and joints. Deal with any oil or fuel staining. This is also the right time of year to book repairs or resurfacing. | Warm, dry weather gives better compaction and a better joint on any repair work. Tarmac laid in July behaves better than tarmac laid in January. |
| Autumn | Clear leaves regularly rather than once at the end. Clear out any channel drain, gully or soakaway before the wet season. Cut back overhanging planting. | Wet leaf mulch stains the surface, holds moisture against it, and feeds moss. A blocked ACO channel in October becomes standing water in December. |
| Winter | Keep water moving off the surface. Use a plastic shovel rather than a metal one for snow. Grit if you need to, but sparingly. | Standing water that freezes is the single biggest cause of cracking. Metal blades chip the surface course and give water an entry point. |
Top tip: If you don’t get time, make it the autumn drainage check because it prevents the damage that costs the most to fix.
Specific problems and what to do about them
Oil and fuel spills
Oil is the one thing that genuinely attacks tarmac rather than just sitting on it. Tarmac is bound with bitumen, and bitumen is a petroleum product, so mineral oil, petrol, diesel and brake fluid all soften and dissolve the binder. A leak that drips in the same spot for months will eventually leave a soft, crumbling patch that has to be cut out.
Deal with it quickly. Soak up what you can with cat litter, sand or a proprietary absorbent granule, leave it for a few hours, then sweep it up. Follow with warm water and a degreaser or washing up liquid and a stiff brush. Do not pressure wash it at close range, because that drives the oil deeper and can strip the surface aggregate at the same time.
If the surface has already gone soft and tacky, washing will not save it. That area needs cutting out and relaying, and it is a small job if you catch it early.
Moss and algae
Moss grows where there is shade and moisture, so it usually starts along a north facing edge, under a tree, or wherever water lingers. It is not damaging the tarmac directly. The problem is that it holds water against the surface and it gets very slippery.
Kill it before you remove it. A proprietary moss and algae killer applied on a dry day and left for the time the label states will do it, and there are plenty of driveway specific products in any builders merchant. Once it has died back, brush it off with a stiff broom. Scraping live moss just spreads the spores.
If it keeps coming back in the same place, the moss is a symptom. Something is keeping that area wet, and it is usually a fall that does not quite work or planting that should be cut back.
Cracks
Hairline surface cracking is common on older driveways and is not urgent. What matters is whether the crack is moving.
A crack that stays the same width year after year is a surface issue. A crack that opens, lengthens, or has broken edges that rock when you press them is telling you the construction underneath has failed, and no filler will hold it. Water is getting into the sub base through it, and in a Kent winter it will freeze and lever the surface apart.
Small isolated cracks can be sealed with a proprietary crack filler as a holding measure. Be honest with yourself about what that is, though. It buys time, it does not fix anything, and it will look like a repair. If cracking is spread across the driveway, the answer is resurfacing, not filling.
Weeds
Weeds do not push up through sound tarmac. They come through joints, along edges where the kerb meets the surface, and through existing cracks. So a weed problem is really an edge problem or a crack problem.
Pull them or treat them, then look at where they came from. Failed edging that has moved away from the surface is the usual culprit, and resetting an edge is a cheap job compared with letting water track down the side of the sub base for another three winters.
Standing water and sunken areas
Water should not sit on a driveway after rain. If a puddle forms in the same place every time, the surface has settled, which normally means the sub base has moved or was never compacted properly there.
This will not fix itself and it will get worse, because standing water works into the surface and freezes. Localised settlement can be planed out and relaid. Widespread settlement means the construction was not right, and the honest answer is a rebuild rather than a patch.
What we actually do, and what we do not
We are a surfacing contractor. We build roads, car parks, estate roads and driveways, machine laid and hand laid, with the sub base and drainage that go under them. That is the work.
We do not sell sealing services and we are not a pothole plugging outfit. If a small repair genuinely solves your problem, we will tell you and quote for it. But most people who contact us about maintenance have a driveway that is fifteen or twenty years old and is asking for a resurface, and the useful conversation is about whether an overlay will work or whether it needs digging out.
An overlay works when the existing base is sound and the levels allow the extra depth without fouling thresholds, gullies or kerbs. Where the base has failed, an overlay cracks in the same places within a year or two, and we will say so rather than take the money.
Common questions
How often should I seal my tarmac driveway? You should not. Sealants and tarmac restorers are cosmetic, they wear unevenly, and they do nothing for the structure. If your driveway is sound and draining, greying is normal and needs no treatment. If it is not sound, sealing it hides the problem rather than solving it.
How long should a tarmac driveway last? Twenty to twenty five years is a realistic figure for a driveway built to the right specification and looked after. Our own residential work uses a 30mm stone mastic asphalt surface course, which we would not expect to need renewing inside 20 to 25 years. Driveways that fail earlier than that almost always had a sub base problem or a drainage problem from day one.
Which jobs can I do myself and which need a contractor? Washing, moss treatment, weeding, leaf clearance and keeping drains clear are all straightforward and worth doing yourself. Anything involving cutting out and relaying, levels, drainage or a soft area caused by oil needs a contractor, because the fix is in the construction rather than the surface.
Is it cheaper to repair or to resurface? It depends entirely on how much of the driveway is affected. A single localised repair is a small job. Once you are repairing several areas, the cost of repeated visits and the patchwork appearance usually make resurfacing the better value option, and it resets the clock on the whole surface rather than one part of it. We quote both where both are viable so you can compare properly.
Can I use rock salt on a tarmac driveway? Sparingly. Salt does not attack tarmac the way it attacks concrete, but heavy repeated use accelerates the freeze and thaw cycle at the surface. Clear the snow first, then grit lightly, rather than relying on salt to do all the work.
Does pressure washing damage tarmac? It can. Held close, a high pressure lance strips the fine material from between the aggregate and leaves an open, rough surface that then holds water and dirt. Keep the lance well back, keep it moving, and use a wide fan.
Get an honest assessment
If your driveway is cracking, ponding or looking tired and you are not sure whether it needs a repair, an overlay or a rebuild, we will come and look at it and tell you which. Quotes are free and in writing.