How the two differ in kind
Asphalt does not fail from the top. It fails when water gets through the surface into the granular base beneath, softens the subgrade, and leaves the surface unsupported — after which traffic breaks it up into the interconnected pattern that ends as a pothole. Everything about maintaining an asphalt surface follows from that: the job is keeping water out.
CRACK FILLING does exactly that. A crack is a direct route from the surface to the base, and a rubberised sealant placed into a cleaned — and where appropriate routed — crack closes it while staying flexible enough to keep moving with it. It is structural maintenance in the sense that matters: it protects the layer that carries the load.
SEALCOATING does something different and worthwhile. It is a thin coating over the whole surface — a few millimetres at most — that restores the black appearance, shields the binder from ultraviolet light and oxidation, and resists fuel and oil spills that dissolve asphalt. What it does not do is add any structural capacity, bridge a crack, or fix anything that has already failed.
Which is why the order is fixed rather than a matter of preference. Sealcoat applied over an unfilled crack does not seal it: the crack keeps moving, and it reflects through the new coating within a season, often before the first winter is out. Sealcoat applied over alligator cracking is worse than useless, because it makes a failed base look like a sound surface for exactly as long as it takes to sell the house.
The factors that actually differ
Show
| Sealcoating | Crack filling | |
|---|---|---|
| What it protects against | Ultraviolet light, oxidation, and fuel or oil that dissolves the binder. Surface ageing. | Water reaching the base. Structural failure. |
| Structural contribution | None. A few millimetres of coating carries nothing. | None directly either — but it preserves the base that does carry the load, which is the whole point. |
| Coverage | The entire surface, at a rate per square metre, usually in two coats. | Linear — measured along the cracks, and the quantity depends on their width and depth as much as their length. |
| Order of work | Second. Always. | First. Always. Sealcoat over an unfilled crack reflects through within a season. |
| Appearance | Dramatic. A sealed drive looks new, which is why it is the one people ask for. | Visible black lines where the cracks were. It looks like maintenance because it is. |
| Frequency | Every few years, and over-frequent application builds a thick brittle layer that cracks and peels on its own. | As cracks appear, which in practice means an annual inspection and a short session each time. |
| What it cannot fix | Cracks, potholes, ruts, alligator cracking, or any base failure. It conceals them briefly. | Alligator cracking — interconnected cracking is base failure, and it needs removal and patching rather than sealant. |
| Weather window | Dry, above a minimum surface and air temperature, with a cure period before traffic and before rain. | The same constraints, plus the crack must be dry and clean inside, which after rain takes longer than the surface does. |
| On new asphalt | Wait. New asphalt needs months to cure and release its volatiles before a coating goes over it. | Not applicable — new asphalt has no cracks. The first ones typically appear after a winter or two. |
| If you only do one | The drive ages slower on the surface and fails on schedule from below. | The drive looks worse and lasts considerably longer. This is the one to do. |
Which one, and when
Choose sealcoating when…
- The cracks are already filled and the surface is sound — this is the correct moment for it.
- Appearance matters: a sale, a commercial frontage, a car park where presentation is part of the product.
- The surface sees fuel and oil, which dissolve the binder and which a sealcoat genuinely resists.
- The asphalt has fully cured and has not been sealed recently enough to be building up a brittle film.
Choose crack filling when…
- There are any cracks at all — this is not a judgement call, it is the first job.
- The budget covers one thing, in which case it covers this one.
- Autumn, before the freeze-thaw season that turns a hairline crack into a pothole.
- The surface is beyond sealing cosmetically but the base is still sound and worth protecting.
Now run your own numbers
This page holds no prices on purpose — a national average is wrong for almost every real project. Quantify both options with your dimensions and your local quotes.
Frequently asked questions
- Which should I do first?
- Crack filling, without exception, and the reason is mechanical rather than aesthetic. A sealcoat is a thin film applied over the whole surface; it does not bridge a moving crack, and the crack beneath keeps opening and closing with temperature and traffic. Within a season — frequently within weeks — the crack reflects through the new coating as a line, and you have paid for a coating that now needs redoing to look right. Worse, the crack has been open the whole time, admitting water to the base, which is the failure you were supposed to be preventing. Fill first, let the sealant cure for the period the manufacturer states, then seal over the top. The sealcoat will still show the repairs faintly, which is the correct trade for a drive that survives.
- Does sealcoating make asphalt stronger?
- No, and it is worth being blunt about this because the marketing frequently implies otherwise. A sealcoat is a coating a few millimetres thick at most, applied over the surface with no bond into the structure and no aggregate carrying load. Structural capacity in an asphalt pavement comes from the thickness and quality of the asphalt itself and from the granular base and subgrade beneath, and a coating adds nothing to any of those. What it genuinely does is slow surface ageing: ultraviolet light and oxygen harden the binder over years, making the asphalt brittle and prone to ravelling, and a coating shields it from both. That is a real benefit with a real return — it is just not strength, and a drive with a failing base will fail on schedule underneath a perfect sealcoat.
- What is alligator cracking, and can either fix it?
- Interconnected cracking in a pattern of small polygons, and neither fixes it, because it is not a surface problem. It means the asphalt above has lost its support: water has reached the base, the subgrade has softened, and the surface is flexing under traffic until it breaks up into pieces. Filling each crack is futile — there are too many, they are moving, and the water is already below. Sealing over it hides it for a season and then the potholes arrive. The repair is a full-depth patch: cut out the failed area back to sound material, investigate and fix the drainage that let water in, rebuild the base, and lay new asphalt. Doing anything else is spending money on the symptom while the cause continues, and the area affected grows every winter.
- How wide a crack can be filled?
- There is a band at both ends. Very fine hairline cracks will not accept sealant — it sits on the surface rather than penetrating — and the usual approach is to rout them to a consistent reservoir first, which gives the sealant somewhere to go and a shape it can flex in. Very wide cracks are a different problem: filling a gap of more than an inch or so with sealant alone wastes material, and the sealant slumps and fails, so a backer rod is placed to control the depth, or the area is patched rather than filled. Between those two, routing and filling is straightforward. The single biggest determinant of whether a filled crack lasts is not the sealant but the preparation — a crack containing dirt, vegetation or moisture gives the sealant nothing to bond to, and it lifts out in one piece the following year.
- How soon can new asphalt be sealcoated?
- Not immediately, and the usual guidance is to wait months rather than weeks — commonly a full season. New asphalt still contains volatile oils that need to leave, and sealing the surface too early traps them, which keeps the asphalt soft and prone to scuffing and tracking. The surface also needs to oxidise slightly so the coating bonds properly; a very fresh, oily surface simply does not hold it. The second reason to wait is diagnostic: the first winter tells you where the drive is going to crack, and dealing with those cracks before the first sealcoat is far more useful than sealing a surface with defects still hidden in it. There is no rush — the whole point of the waiting period is that new asphalt does not yet need the protection.
- Can sealcoating be done too often?
- Yes, and over-sealing is a genuine failure mode rather than merely wasted money. Each coat adds a layer that does not bond to the asphalt the way asphalt bonds to itself, and repeated coats build a thickening film with different thermal movement from the surface beneath it. Past a certain accumulated thickness that film becomes brittle, and it cracks in a fine web of its own and peels away in sheets — leaving a surface that looks far worse than an unsealed one and that has to be stripped before it can be treated properly. Intervals of several years are typical, and the right trigger is condition rather than the calendar: a surface that has greyed and is starting to show fine aggregate at the top has lost its coating, and one that is still black has not.
- What weather does each need?
- Both need dry conditions, a surface and air temperature above a stated minimum, and a cure window before rain or traffic — and the crack work is the fussier of the two. A surface can look dry within an hour of rain while the inside of a crack is still wet, and sealant placed into a damp crack does not bond; it skins over, traps the moisture, and lifts out later in a single strip. Hot-applied sealants add a temperature requirement of their own and are worked within a range rather than simply above a minimum. Sealcoat needs the full cure period before traffic, which is longer than it looks dry for, and a shower during that window will wash an uncured coating off the drive and onto everything downhill of it.
- When is the drive past maintenance?
- When the base has gone, and the signs are visible before the potholes are. Interconnected alligator cracking over a significant area, rutting along the wheel paths, edges that crumble away rather than crack, and a surface that visibly deflects when a vehicle passes over it all point the same way: the structure beneath is no longer supporting the surface. At that stage crack filling is chasing a moving target and sealcoating is cosmetic, and the money is better spent on reconstruction — or, if the base is sound and only the surface is worn, on an overlay. The useful question before committing to either is whether water is getting in and where from, because a drive rebuilt over the same drainage problem fails the same way on the same timescale.