Pothole repair: does patching work, or do you need to repave?

Patching works when the base under the pavement is still sound. Federal pavement research found roughly 69 percent of test patches were still in service at final evaluation, with a median age over 18 months. When potholes keep coming back in the same spots, the base has failed and no patch will hold.

Telling those two situations apart is most of the job. The rest is using decent material and doing the work in the right season. Both are covered below, along with where asphalt repair stops being worth it and repaving takes over.

Why do potholes form?

They start as cracks. Minnesota DOT research puts it plainly: pothole formation is mainly caused by delayed response to fixing common pavement distresses in the early stage, and the most common of those is cracking. Water gets into the crack, freezes, expands, and works the pavement apart from the inside.

The physics are simple enough to picture. Water that freezes into ice takes up about nine percent more room than it did as a liquid, and it does not ask permission from the asphalt around it. Every thaw lets more water in. Every hard freeze pries the opening wider.

Billings runs that cycle often. NOAA’s engineering weather data for Billings Logan International Airport lists an average of 81 freeze-thaw cycles per year across a 30 year record. That is 81 times the temperature drops below freezing and comes back up, and each pass does a little more damage to any crack that was left open.

Traffic finishes the job. Once water has softened the base, wheel loads punch the weakened pavement down and the surface finally breaks through. The hole appears in spring, but it was built over the winter.

When will a patch actually hold?

A patch holds when the pavement around it is still structurally sound and the hole is a local defect rather than a symptom. Good candidates are isolated, have firm edges, and sit on ground that is not soft underfoot. Bad candidates come back every year in the same three feet of drive lane.

The other half is material and timing. Minnesota DOT found that repairs done in late spring and summer with hot mix asphalt are the most durable and may last more than one winter season, while cold mixtures used for winter patching have poor mechanical properties and need frequent re-repairs. Winter patches are triage, not repair.

The Foundation for Pavement Preservation puts patch durability at 2 to 12 years on pavement in good to fair condition, and 1 to 4 years on pavement in poor condition. Same crew, same material, very different outcomes, decided entirely by what the patch is sitting in.

Which patching method lasts longest?

The federal Strategic Highway Research Program placed 1,250 pothole patches across eight test sites in the United States and Canada and tracked how they held up. Its finding surprised people: throw and roll proved just as effective as the more labor-intensive semi-permanent procedure, as long as quality material was used.

Method	What happens	How it performs
Throw and go	Material dumped in the hole, no prep, no compaction	Poor, generally does not last
Throw and roll	Same fill, then compacted by rolling a truck tire over it	Effective with quality mix
Spray injection	Machine blows the hole clean, then injects emulsion and aggregate under pressure	Comparable to throw and roll
Semi-permanent	Hole cleaned, edges cut back to sound asphalt, compacted with a vibratory plate	Effective, higher labor cost
Full-depth patch	Failed pavement and base removed and rebuilt, hot mix placed in lifts	The repair for a failed base

Two things are worth pulling out of that study. The first is that material quality mattered more than technique. The only repair types that clearly underperformed were inexpensive, low-quality cold mixes, and those failed by ravelling, usually inside a month.

The second is climate. Patches at dry-freeze sites survived at 93 percent against 48 percent at wet-freeze sites. Billings is cold and dry, averaging around 14 inches of precipitation a year, which is the favorable half of that split. Patches here get a better shot than the same work would in a wet climate.

One correction worth making, since it circulates widely: spray injection did not outperform the other methods in that study. It performed comparably to the control patches at every site, and its crew productivity was about the same as throw and roll. It is a good tool, not a magic one.

How do you tell the base has failed?

Look for alligator cracking. The Washington Asphalt Pavement Association describes it as a series of interconnected cracks caused by fatigue failure under repeated traffic loading, and points to inadequate structural support as the primary cause: a weak base, poor drainage, or loading the pavement was never built for.

The pattern tells you where you are. Isolated alligator cracking over a small area means localized loss of subgrade support, and the fix is to remove the cracked pavement, dig out and replace the poor subgrade, improve drainage if needed, and patch over the repaired base. That is a real repair with a long life.

Widespread alligator cracking is a different message. When it covers a large share of the surface, the pavement structure itself has failed. Patching individual holes in that pavement buys weeks. The published guidance is to mill and fill the surface, and add an overlay if that still does not give enough structure.

There is a simple field version of this. Go out and look at the area after a rain. Standing water, spongy spots, and patches that have sunk below the surrounding surface all point at the base rather than the asphalt.

Does crack sealing really prevent potholes?

It prevents most of them, because potholes are cracks that nobody sealed. Federal highway guidance credits crack and fog seals with extending pavement life by one to four years, and puts them at their most useful on pavement still in excellent to good condition.

Research from the national center for asphalt technology sharpens that. On pavement in good condition, with under 5 percent cracking before treatment, crack sealing had a mean time to failure of more than seven and a half years, against under five years for crack filling. On pavement already in fair or poor shape, the benefit dropped sharply.

The lesson is about timing rather than product. Crack sealing is cheap and effective while the pavement is still mostly fine, and close to pointless once the surface is coming apart. A driveway or lot checked every spring and sealed as cracks appear rarely produces holes at all.

A worked federal example of a municipal street cycle looks like this: seal the cracks in year two, apply a surface treatment in years five, twelve and eighteen, then mill and replace the surface at year twenty-five. That is what a maintained pavement schedule looks like.

Can seal coating fix a pothole?

No, and treating it as a repair costs money twice. The Colorado Asphalt Pavement Association describes seal coating’s purpose as prolonging existing pavement life by slowing surface oxidation, water intrusion and petroleum degradation. Protection for sound asphalt, in other words.

Its own best practices put crack filling and patching before coating, not instead of it. Cracks get filled with hot rubberized sealant first, and failed pavement gets removed to the full depth of the damage and replaced. Only then does the coating go on.

Timing matters here too. New asphalt has to cure before its first coat, and the published rule is 30 to 90 days at 70 degree daytime temperatures. In Montana that usually pushes the first seal coating on a fall pave to the following summer. Our seal coating cost and schedule guide covers the published prices and the two to three year cycle. Rushing it traps the oils and leaves the surface soft.

When does repaving beat patching?

When patching turns into an annual expense. Minnesota DOT notes that on high traffic surfaces, resurfacing a section can be more cost-effective than patching potholes every summer. The same logic works on a commercial lot where the same four areas fail every spring.

Federal guidance lines the options up by condition. Crack and fog seals suit excellent to good pavement and add one to four years. Heavier surface treatments like chip seals add three to seven. Once pavement reaches fair or poor condition, thin and ultrathin overlays add five to twelve years, and below that the surface needs replacing.

That is the test to apply to your own surface. If most of it is sound and a few spots have failed, patch them properly and get back to maintenance. If failure is everywhere, patching is the expensive option and repaving is the cheap one, even though the invoice says the opposite.

Season sets the schedule either way. Montana DOT holds plant mix paving to a November 1 cessation date and stops when the surface temperature is under 35 degrees, so permanent hot mix work runs roughly mid-April to the end of October.

Who fixes potholes in Billings?

The city handles public streets and you handle everything on your property. Billings Public Works maintains more than 1,230 lane miles of paved streets and runs annual crack seal, chip seal and overlay programs, repairing 35 or more miles of street a year. It also takes pothole reports directly through its Public Works page.

That line matters for driveways and parking lots. The apron where your driveway meets the street may sit in city right of way, but the drive itself, and every private lot in town, is on the owner. Nobody is coming to patch the hole by your dumpster.

If you are weighing the whole surface rather than one hole, the concrete versus asphalt comparison covers what each material asks of you over its life, and the asphalt driveway cost guide has resurfacing and replacement ranges.

FAQ

Does patching a pothole actually work? Yes, when the base under it is still sound and the material is decent. Federal pavement research found about 69 percent of test patches were still in service at final evaluation, with a median age over 18 months. Cheap cold mix is what fails, often ravelling out inside a month.

Why does the same pothole keep coming back? Because the hole was the symptom. If the base under the pavement has lost strength, water keeps getting in and the patch keeps working loose. The repair that holds removes the failed pavement and the bad base underneath, then rebuilds both before new asphalt goes down.

What is alligator cracking and what does it mean? It is the interconnected pattern that looks like chicken wire or reptile skin. Pavement engineers class it as fatigue failure from inadequate structural support, usually a weak or wet base. Isolated patches can be dug out and repaired. Widespread alligator cracking means the pavement structure is done.

Will crack sealing stop potholes from forming? It stops most of them. Potholes start as cracks that were never sealed, and federal guidance credits crack and fog seals with adding one to four years of pavement life. Research also shows sealing works far better on pavement that is still in good condition than on pavement already failing.

Can seal coating fix potholes? No. Seal coating is a surface protectant that slows oxidation and keeps water off sound asphalt. Industry best practice calls for filling cracks and removing failed pavement to full depth before any coating goes down. Sealer over a pothole hides it for a few weeks.

When is repaving cheaper than patching? Once patching becomes an annual line item. If potholes keep returning in the same areas, or alligator cracking covers a large share of the surface, an overlay or full replacement costs less over a few years than repeated repairs. Federal guidance puts thin overlays at 5 to 12 years of added life.

When can potholes be repaired in Montana? Permanent hot mix repairs need the paving season, which Montana DOT effectively runs from April 15 to November 1 with a 35 degree surface temperature floor. Winter repairs use cold mix and are temporary by design, often lasting only weeks before they need doing again properly.

Get the surface looked at before spring

The cheapest version of this job is the one done before the hole appears. Ostermiller Construction handles asphalt repair, crack sealing, seal coating and parking lot striping across Billings, Laurel, Lockwood and the Yellowstone Valley. Ask for a free estimate and we will go over the whole surface, mark what is a patch and what is a base problem, and price both.