Most bitumen driveway pothole repair jobs are within reach of a homeowner with a wire brush, a bag of cold mix and a couple of free hours. If the hole is smaller than a dinner plate, shallow, and the bitumen around it is still solid, you can patch it this weekend. If the edges crumble when you touch them, you can see loose gravel at the bottom, or the same spot has failed twice, patching is a waste of a Saturday. The problem sits below the surface, and a patch will not reach it.
Here is how to tell those apart, and how to do the job properly.
Why bitumen driveways develop potholes and cracks
Potholes almost never start as potholes. They start as a crack.
Queensland's Department of Transport and Main Roads lists the causes as untreated crocodile cracking, moisture getting into the pavement layers through a cracked surface, and the base breaking up under heavy loading. Water is the thread running through all of it. Once it gets past the seal it softens the crushed rock underneath, traffic pumps the wet material out sideways, and the surface collapses into the void.
That matters more here than in most of the country. Brisbane averages 1,065 mm of rain a year and roughly 57 per cent of it falls between December and March. Then there is the soil. The QBCC notes most Queensland homes sit on reactive clay soils that expand and contract with moisture, and that on the most reactive sites in the southeast, ground movement has been recorded up to and in excess of 100 to 150 mm. Ground that moves that much will crack whatever is laid over it.
Freeze and thaw, the cause every American pothole guide leads with, is irrelevant here. Ours come from water and load. Surface cracks are the same problem earlier on, so seal them and the pothole never forms.
What you will need before you start
For a pothole: stiff broom, wire brush, bagged cold mix bitumen patch, a hand tamper or hired plate compactor, a trowel, and gloves and boots you do not care about. Cold mix is sticky and it does not wash off.
For a crack: wire brush, an old screwdriver, pourable bitumen crack filler and a spatula.
Boral's Bitupack and Dingo's Bitumen Quick Repair both put around 60 kg over one square metre at 25 mm thick, so three 20 kg bags per square metre. Most driveway potholes need one or two. Buy the spare anyway, because running out halfway through a layer wrecks the patch.
Assessing the damage: is this a DIY job or not
Grab a dinner plate and hold it over the hole. That is your threshold, roughly 250 to 280 mm across. If the damage sits inside the plate and it is no deeper than the length of your thumb, call it 50 mm, you are looking at a patching job.
Past that, three things push it into professional territory.
Crumbling edges. Press the bitumen around the rim with a screwdriver. If it breaks away, there is no sound material for the patch to bond to and it will lift at the join.
Exposed base. Loose grey gravel at the bottom means the failure has gone through the surfacing into the pavement structure. Filling the top changes nothing.
A repeat failure. Same hole twice means the cause is underneath and you have not touched it. TMR is direct on this: pothole patching is repairing a hole in the sealed roadway surface that is in otherwise sound condition, and potholes in pavement showing cracking, shoving or rutting need a different method entirely.
For scale, TMR crews log a pothole on a state road once it passes 100 mm across or 30 mm deep. If that is what you are seeing, what to do if the damage is beyond a DIY patch is the more useful read.
Step by step: cleaning and preparing the area
This is the step nearly everyone rushes, and it is why most home patches fail inside a year.
- Dig out everything loose. Broken bitumen, gravel, dirt, weeds, the lot. Keep going until what is left does not move.
- Square up the edges. TMR's method calls for forming a vertical face on the edges and shaping the hole into a rectangle. Cut back to solid bitumen with a spade or bolster chisel. Feathered edges give the patch nothing to lock against.
- Get it dry and clean. Sweep it out, then brush the dust off the faces. Standing water stops the cold mix bonding, so if it rained overnight, wait a day.
- Check underneath. If the bottom is soft or muddy, dig it out and compact road base in first. Cold mix is a surfacing product, not a structural one.
Do not patch in the rain or on a cold morning. Bondall specifies 5 to 40 degrees for its Gripset Betta crack filler, and cold mix compacts better warm. A mild dry day in late winter or early spring is close to ideal.
Step by step: filling and compacting the pothole
Cold mix does not set the way concrete does. It cures by being squashed, so compaction is the whole job.
- Shovel in the first layer, then check your product's maximum layer depth, because it varies more than you would expect. Dingo specifies no more than 30 mm per application and 50 mm total. Boral gives 30 mm per layer for Bitupack, 25 to 50 mm for UltraPatch. QPR allows 50 mm layers with no cap on total depth provided each is compacted.
- Compact that layer. Hand tamper, plate compactor, or at a pinch a car wheel driven slowly over a board. Keep going until the tamper stops leaving marks. TMR uses that exact test: compaction is adequate when the final passes leave no impressions on the restored surface.
- Repeat until you are slightly above the surrounding surface. Overfill by about 5 mm and dome it a little, because it will settle.
- Compact flat, finishing level with the driveway. TMR's tolerance on a road patch is within 5 mm of the surrounding surface. A patch sitting high catches mower blades. One sitting low collects water and fails again.
Step by step: sealing a surface crack
Much faster. Half an hour covers a driveway's worth of hairline cracks.
Dig the crack out first. Wire brush along it, use a screwdriver tip on the deeper sections, and pull out any grass or moss. Filler will not bond to dirt or vegetation.
Then run the pourable filler along the full length, not just the wide part. Cracks travel from their ends. Smooth it flush and leave it.
Two independent sources land on the same ceiling for width. Bondall says of its asphalt crack filler that it is not recommended to fill cracks wider than 20 mm, and TMR's routine maintenance specification describes crack filling as being for cracks typically not wider than 20 mm. Anything wider means the base is moving, and filler will crack back open along the same line.
Do not use crack filler in a pothole either. No aggregate, so it slumps, holds water and pulls out under a tyre. Ongoing bitumen surface maintenance covers timing, and preventing potholes and cracks before they start covers the rest.
How long the repair needs to cure
You can drive on it straight away. Boral, Dingo and QPR all state their cold mix can be opened to traffic immediately after compaction, and driving over the patch is part of the curing process rather than a risk to it. Your tyres finish what the tamper started.
Full hardening is slower. Dingo describes its product hardening gradually over several weeks depending on the application and weather, as the bonding agent dries out.
The number most people miss: both Dingo and QPR say to wait six months before sealing over the top. Seal earlier and you trap material that is still working its way out. Check the bag, because guidance differs between products.
Common mistakes that cause a patch to fail early
Under-compacting is easily the most common. A loosely filled hole looks finished on Sunday afternoon and starts sinking within a fortnight.
Patching wet or cold. Water at the bond line, or mix too stiff to compact properly.
Feathered edges. Without a vertical face in sound bitumen, the edge of the patch is its weak point, and that is where water gets in next.
Filling too deep in one go. The top looks solid while the bottom stays loose.
Ignoring what caused it. If a downpipe discharges onto that spot, or a puddle sits there after every storm, your patch fails the way the original surface did. TMR's checklist for pothole patching opens with "what has caused the defect?" for this reason.
When bitumen driveway pothole repair becomes a contractor's job
Be clear-eyed about what a DIY patch is. It is a stop gap. It keeps water out and stops a hole getting worse, and on a small, isolated pothole in sound bitumen it can hold for years. It is not a structural repair, and no amount of cold mix fixes a failing base.
Get a professional assessment when:
- The hole is wider than a dinner plate or deeper than about 50 mm
- The edges crumble under screwdriver pressure
- You can see gravel base or subgrade at the bottom
- The same spot has failed more than once
- There is interconnected cracking across an area, not a single line
- The surface is sinking or holding water after rain
At that point the real question is whether resurfacing or replacement is the better option, and the answer turns on the base rather than anything visible from standing up. Signs your driveway needs full replacement is the honest version of that list.
One last thing if the damage is near the street. Across South East Queensland the crossover between your boundary and the kerb is your responsibility, not the council's, even though it sits on council land. Brisbane City Council states property owners are responsible for the construction and ongoing maintenance of their driveway, including the adjacent kerb and channel, and the Gold Coast, Ipswich and Sunshine Coast councils say much the same.
Not sure if you are looking at a patch job or a base problem? Get eyes on it before you spend money on either. Road Ways works across Brisbane, the Gold Coast, Sunshine Coast, Ipswich and Toowoomba. Have a look at professional bitumen driveway repairs, or get in touch for an assessment.