Asphalt driveway installation: base, drainage, mat, and edges

What actually makes a driveway last

An asphalt driveway is a flexible pavement, a thin asphalt mat riding on a compacted stone base over the native soil. Most people buy the mat. They ask how many inches of black, and they price the whole job on that one number. The mat is the part that fails last.

The base and the drainage decide how long the driveway lasts, not the asphalt thickness on its own. A 2 in mat on a well-built, well-drained 8 in base will outlive a 4 in mat poured on wet clay with nowhere for water to go. The stone under the asphalt carries most of the load down to the soil, and a common rule of thumb gives the base on the order of half to two-thirds of the section's real strength. Skimp there and the asphalt is flexing over a foundation that keeps moving, which is the start of every early failure.

Two jobs sit on either side of this one, and they are where the driveway is won or lost. How thick the whole section needs to be for the traffic and the soil is its own decision, covered in the pavement thickness design guide. How you compact the subgrade and the base and prove them before you pave is the base and subgrade compaction guide. This guide is the install itself, from the string line to the first sealcoat, and it leans on both of those being done right.

The install sequence, start to finish

A driveway goes in roughly the same order every time, and the order is not negotiable, because each step buries the one before it. Lay out the shape and set the grades. Excavate to depth and haul off the spoil. Prep and proof the subgrade, fix the soft spots. Place and compact the aggregate base in lifts. Check the grade and the drainage one more time, because this is the last clear look you get at the dirt. Pave the asphalt hot, hand-work the edges and the tie-ins, then roll the mat to density inside the cooling window. Taper the edges, backfill against them, and let it cure before traffic.

Each handoff buries evidence. Once the base covers the subgrade you cannot see the soft spot anymore, and once the mat covers the base you cannot see whether it was compacted. So the inspections happen before the cover, not after.

The mistakes that cost the most are the ones that skip a step to save a day. Paving over a soft spot that should have been undercut, or over a base that never got compacted, hides the problem under the mat where it costs ten times as much to reach later. The crew that paves on a Friday over a base they could not test is the crew that comes back the next spring.

Site layout, width, and the grade that sheds water

Layout sets the shape and the grades before a machine moves dirt, and the grade is the part that decides the life of the driveway. The finished surface has to slope so water runs off and away from the house and the garage, never toward them. A common minimum is about 1 percent, roughly 1/8 in of fall per foot, but 2 percent, about 1/4 in per foot, is the number most pavers build to, because it still sheds water after the surface settles and the snow piles up. Below about 1/2 percent the surface ponds, and ponding is where failures start.

Slope away from the structure is the rule that protects the building, not just the driveway. Pitch the apron at the garage so water leaves the door, and crown or cross-slope the run so it does not channel down the middle and stand. Where the lot forces the grade to fall toward the garage, you are into a trench drain or a channel drain at the door, and that is a decision to make before paving, not a fix bolted on after.

Width is a comfort and a resale call. A single-car drive commonly runs around 10 to 12 ft, a double around 20 to 24 ft, with extra at the approach and at the garage for turning and door swing. Plan the room to back and turn now, because asphalt added later in a strip rarely ties in clean. Keep the hedge and the lawn back off the edge so the mat has soil to lean on. That matters more than it looks, as the edge section gets into.

Excavation: digging out to the full section depth

Excavation removes the topsoil, the sod, and any old pavement or soft fill down to the depth the section needs, and that depth is the sum of the mat and the base plus any undercut the soil forces. For a residential drive with a 3 in mat and an 8 in base, you are digging on the order of 11 in of usable section below finished grade, and deeper where you have to cut out soft soil. Topsoil and organics never stay under pavement. They rot and compress, so they all come off.

Set the finished surface elevation first, then work down from it. Get that wrong and either the driveway sits proud of the garage slab and the lawn, or it ends up low and collects water, and there is no fixing it once the base is in. Stake the finished grade, subtract the mat and the base, and that is the subgrade elevation you dig to.

Haul-off is real money and real planning. Old asphalt and concrete can often be crushed and recycled rather than landfilled, and a clean excavation gives you somewhere to put the base instead of fighting spoil piles. Strip wide enough to build the edges and the restraint, not just the width of the finished mat, because the edge needs ground beside it to be built on.

The subgrade: proof it before you build on it

The subgrade is the native soil the whole driveway rests on, and it is the number-one place driveways fail. Everything above it inherits its strength, so a soft, wet, or organic subgrade dooms the section no matter how good the stone and the asphalt are. Before any base goes down, the subgrade gets proof rolled: a heavy loaded truck driven slowly across it while you watch for movement. Where the ground pumps, waves, or ruts under the tires, it is too soft to build on.

Soft spots get undercut, dug out and replaced with compacted structural fill or extra stone, sometimes over a geotextile or geogrid that separates the soft soil from the clean base and keeps the two from mixing. How deep you go is a judgment call on a residential job and a geotech call on anything engineered, because a soft pocket can be a foot deep or it can be the top of a saturated layer that runs much deeper. Either way you do not pave over it.

Moisture and compaction are the rest of the work, and how to hit the density and prove it is the base and subgrade compaction guide. The short version for the field: a clay subgrade that is too wet will not hold density and pumps under the roller, and a driveway built on it moves within a season or two. Get the subgrade right and the rest of the job is straightforward. Get it wrong and nothing above it can save you.

The aggregate base: the stone that carries the load

The aggregate base is the compacted crushed-stone layer between the subgrade and the asphalt, and it does most of the work of spreading each wheel load into a pressure the soil can take. For a residential driveway it commonly runs about 6 to 8 in of dense-graded crushed stone, more on weak or wet soils. The exact depth ties to the soil strength and the traffic, which is the pavement thickness design guide, but on most residential jobs 6 to 8 in over a sound subgrade is the working range.

Dense-graded is the spec word that matters. It means a blend of sizes from a top size down through sand to a controlled amount of fines, which packs into a tight, interlocked mass that is strong and sheds water. Angular crushed stone locks together and resists shoving where rounded gravel rolls and rearranges, so a cheaper rounded material is not a free swap. Let too many plastic clay fines into the base and it holds water and softens, which is the opposite of what you want under a driveway.

Compaction goes in lifts, not all at once, because a roller's energy only reaches so deep. Place the stone in layers the equipment can actually compact, commonly a few inches up to 6 to 8 in per lift depending on the roller, wet it near optimum moisture, and roll each lift to density before the next. How you test and prove that density, and which Proctor the spec measures it against, is the base and subgrade compaction guide. The driveway version of the rule is simple: a base that was not compacted in lifts is a base with a soft bottom you cannot see.

How do you keep water out of a driveway?

You keep water out of a driveway by giving it a path to leave at every level: off the surface by slope, off the base by grade and an outlet, and away from the edges so nothing stands against them. Water is the thing that kills asphalt, and it does it from underneath more often than from the top. A section that cannot drain softens at the base, loses the strength it had dry, and the mat cracks over the moving foundation.

Three drainage jobs run through the whole install, and they keep coming up because they keep failing. The surface has to shed water, which is the 1 to 2 percent slope and the crown or cross-slope from the layout. The base has to drain, sloped to daylight at a ditch or a slope or tied to an edge drain, so it does not store water against the subgrade. And the edges cannot trap water or sit in a low spot, because a saturated edge is the first part of the mat to fail.

The quiet failure is a driveway that looks pitched but ponds after it settles, or a base that holds water because it is flat or full of fines. Walk it after a rain. Standing water anywhere on a new driveway is a problem to fix now, not a cosmetic complaint, because every gallon that does not run off is working its way into the base. This is the recurring theme of the whole job. The asphalt is the easy part. The water is the enemy.

How thick should an asphalt driveway be?

A residential asphalt driveway commonly gets 2 to 3 in of compacted asphalt over 6 to 8 in of compacted aggregate base. Two inches compacted is a working minimum for cars only, 3 in is the number most pavers build for durability and for the occasional delivery truck, RV, or moving van, and a heavier-use or commercial drive goes thicker still. The base depth matters as much as the mat, which is why the two get quoted together.

Watch the word compacted. Asphalt loses roughly a quarter of its loose height when it is rolled, so a 3 in compacted mat goes down looser than 3 in, and a contractor quoting three inches should mean after compaction, not before. A mat measured loose and rolled to 2 in when you paid for 3 is the most common quiet shortfall on a driveway, and it is invisible once the job is done.

Thickness alone does not buy a long driveway, which is the through-line of this guide. A thin mat on a strong, well-drained base beats a thick mat on a soft one every time. Size the section to the soil and the traffic, which is the pavement thickness design guide, then hold the contractor to the compacted thickness and the base depth that were quoted. The numbers here are typical residential figures. The project spec and the soil control the real ones.

Single lift vs binder and surface course

Most residential driveways go down as a single lift of asphalt, one pass of mix laid and rolled to the finished thickness. At 2 to 3 in that works fine, and it is the common residential build. The single lift is simpler, cheaper, and there is no cold joint between layers to worry about.

A thicker driveway, or one carrying real truck traffic, often gets built in two courses: a coarser binder course on the bottom for structural thickness and a finer surface course on top for the ride and the seal. The split shows up once the total asphalt gets past roughly 3 to 4 in, because a single lift that thick is hard to compact evenly all the way to the bottom. The binder carries the structure with a cheaper, coarser mix, and the surface course is the finer, denser mix that takes the tires, the water, and the weather.

Which build you need follows the thickness, which follows the traffic and the soil. A car driveway rarely needs two courses. A long shared drive, a drive that takes delivery trucks or an RV, or a light-commercial lot often does. The mix selection by layer is its own topic, but the field rule is that thick asphalt is placed and compacted in lifts the equipment can actually reach, the same logic as the base.

Paving the mat: temperature, the paver, and the joints

Paving puts the asphalt down hot and even, and the temperature is the clock that runs the whole operation. Hot-mix asphalt is laid and worked in a window that commonly starts up around 275 to 300°F at delivery for many dense-graded mixes, and it has to be compacted before it cools out of the range where it will still move. Mix that arrives cold, or sits too long in the truck, is losing the job before it ever hits the ground.

On a driveway a paver lays the main field and a crew hand-works the rest. The machine pulls a uniform mat at a set thickness and grade, and the crew rakes and lutes the edges, the tie-ins, and the spots the machine cannot reach. Hand-work is where driveways are made or ruined, because the raker controls the edges and the transitions the paver leaves rough. Segregation, where the coarse rock separates from the fines in a streak, and a ragged hand-raked edge are the tells of a rushed crew.

Joints are the weak line in any mat, so you want as few as possible on a driveway and the ones you have built tight and hot. A cold longitudinal joint between two passes, or the joint where the new mat meets the garage apron or the street, is where water gets in first if it is not compacted well. Lay the field in as few passes as the width allows and work the joints hot. How the mat then gets rolled to density inside the cooling window is the asphalt compaction guide, and it is the step that locks in everything the paver just placed.

Compaction: rolling the mat to density before it cools

Compaction turns a loose, placed mat into a dense, durable driveway, and it has to happen inside the temperature window while the asphalt is still workable. A roller follows the paver. The breakdown rolling does the main densifying while the mat is hottest, and the finish rolling smooths it and removes the roller marks as it cools. Roll it too cold and you cannot reach density no matter how many passes you make.

Density is the whole point, because the air voids left in an under-compacted mat are interconnected and let water in. A mat left a few points low on density looks fine on day one and then ravels, cracks, and ages early, because water and air are getting into it. The target is to drive the voids down into the durable range while the heat is still there to let the stones move into place. This is the same physics on a driveway as on a highway, just at a smaller scale.

On a tight residential job the edges and the hand-work areas are where compaction gets missed, because the big roller cannot reach them and a plate compactor or a small roller has to. Those are exactly the spots, the edges and the joints, that fail first. The cooling window, the roller pattern, and the density target are the asphalt compaction guide. For the install, the rule is that the rolling has to keep up with the paver and finish before the mat goes cold.

Why is my asphalt driveway cracking at the edges?

Asphalt driveways crack and crumble at the edges because the edge is the weakest part of the mat and the part with the least support under and beside it. Out in the field of the driveway the mat is confined on all sides by more asphalt. At the edge it is unconfined, so a wheel run off the side, or a base that was not compacted all the way to the edge, shears the asphalt. It cracks, then ravels, then breaks away.

The fixes are all about supporting that edge. Build the base out past the asphalt so the mat is not sitting on the very lip of the stone. Taper or bevel the edge, commonly to something like a 45 degree wedge rather than a vertical cut, so the edge has a wider foot and is less likely to break under a tire. Then backfill against it with soil, sod, or a paver or timber restraint so the edge is held laterally and water cannot wash the soil out from under it. An edge left vertical, with bare base showing and no backfill, is a raveling edge waiting to happen.

Water makes it worse, especially where it freezes. Rain or snowmelt that seeps under an unsupported edge softens the base, and in a cold climate that trapped water freezes, expands, and lifts the edge, then thaws and drops it, working the cracks open a little more each cycle. Keep water off the edge and keep the edge supported and the most common driveway complaint mostly goes away.

Transitions: the garage apron, the street, and concrete

The tie-ins are where a driveway meets something it did not pour, the garage slab, the street, a concrete walk or apron, and they are both the hardest to get right and the first place water tries to get in. A transition that is high, low, or open lets water pond or run under the mat, and it is the joint a homeowner notices every day.

At the garage, the asphalt usually ties to a concrete apron or directly to the slab, and the grade has to carry water away from the door, not pool at it. The asphalt is brought up to meet the concrete flush or slightly below, compacted tight against it, and the joint is the thing to keep sealed over the years, because asphalt and concrete move differently and the joint between them works open. At the street, the apron ties into the existing pavement or the curb, often with a thicker section, because that is where every vehicle enters and turns, concentrating load on the one spot.

Where asphalt meets concrete anywhere, treat the joint as a maintenance item from day one. The two materials expand and contract at different rates, so the joint is never permanent, and a sealed joint that gets re-sealed lasts where an open one lets water into the base underneath. Build the transitions hot and tight, grade them to drain, and plan to re-seal the asphalt-to-concrete joints as part of the upkeep.

How long before you can drive on a new asphalt driveway?

You can usually drive on a new asphalt driveway within about 24 to 72 hours, once the surface has cooled and firmed enough to take traffic without scuffing. That is dry enough for cars, not fully cured. Asphalt keeps hardening for months as the lighter oils in the binder work out and the mat stiffens, so the first weeks are when it is softest and easiest to damage.

The damage on a fresh driveway comes from concentrated and turning loads, not rolling ones. Power-steering the wheel while the car sits still twists the soft surface and leaves marks. A jack stand, a motorcycle kickstand, a heavy dumpster leg, or a trailer tongue jack can punch a dent into a warm new mat. Parking in the same spot every day in the first hot weeks can leave a depression. Keep point loads off it, do not turn the wheels while stopped, and stay off the very edges until it has firmed up.

Heat and the season set the real cure time. A driveway paved in hot summer weather stays soft longer in the first days and needs more care, while cool fall weather firms the surface faster but cures the mat slower overall. Hedge the homeowner's expectations to the weather: longer in the heat, gentle on it for the first month either way, and no heavy or static loads until it has had time to harden.

When should you seal a new asphalt driveway?

You seal a new asphalt driveway for the first time after it has cured, commonly somewhere in the 6 to 12 month range, and not before about 90 days at the earliest. Fresh asphalt needs to cure and release its lighter oils before a sealcoat goes on, because sealing too early traps those oils, keeps the mat from hardening properly, and the coating does not bond or last the way it should. New asphalt does not need sealing to survive its first winter. It needs to cure.

Sealcoat is maintenance, not structure. It is a thin protective coat that shields the surface from oxidation, water, fuel, and UV, and it renews the black look, but it adds no strength to the mat or the base. After the first application, a common cycle is to re-seal every few years, often cited in the range of every 2 to 4 years, based on wear and how faded and porous the surface looks rather than on a fixed calendar. Over-sealing is a real failure too: piling on coat after coat builds a thick skin that cracks and peels.

The timing and the cycle are judgment calls hedged to the climate and the traffic, so do not seal by the calendar alone. Seal when the surface starts to gray and lose its fines, when water stops beading and starts soaking in, and after the mat has fully cured the first time. A driveway in a harsh freeze-thaw climate or one that sees heavy use earns its sealcoat sooner. A lightly used drive in a mild climate can wait.

Crack sealing, potholes, and cold patch

Cracks are the first repair a driveway needs and the one that pays off most, because a sealed crack keeps water out of the base and an open one lets it in. Clean the crack of dirt and growth, then fill it with a flexible crack sealer made for asphalt, not a thin driveway sealer that runs into the gap and disappears. Hairline cracks can wait for the next sealcoat. Cracks wide enough to take water get sealed on their own as soon as you see them, because the freeze-thaw that follows opens them fast.

Potholes form when water has already gotten into the base, frozen, and broken the mat up from below, so a pothole is a base problem surfacing, not just a hole in the asphalt. A clean repair squares up the hole to sound material, down to a firm bottom, then fills and compacts it. Hot-mix is the durable patch where you can get it. Cold patch, the bagged premixed asphalt, is the field and winter repair: it goes in cold, tamps down, and holds as a temporary to semi-permanent fix when hot-mix is not available or the weather is wrong for it.

The honest part of patching is that a repair only lasts as long as the base under it. Patch a pothole over a soft, wet base and it comes back, because the cause is below the patch. If a driveway is breaking up in more than a spot or two, the question stops being how to patch and becomes whether the base failed, which is the overlay-versus-replace decision.

Overlay or full replacement?

Whether you can overlay an old driveway or have to tear it out comes down to one question: is the base still sound? An overlay, a new layer of asphalt over the existing one, works when the old mat is worn, faded, and lightly cracked but the structure under it is still solid. It is cheaper and faster than a full rebuild, and on a sound base it buys many more years.

An overlay is the wrong answer when the driveway is failing from the base up. Widespread alligator cracking, the interconnected pattern in the wheel paths, ruts, and areas that pump or feel soft underfoot are structural signals, and a new mat over a failing base just cracks again as the old distress reflects straight through it. Reflective cracking, where the old cracks telegraph up through the new overlay within a year or two, is the classic sign someone overlaid a driveway that needed replacing.

Full replacement, dig out the old mat and often the base, fix the subgrade, and rebuild the section, is the answer when the base is gone or the drainage was never right. It costs more up front, and it is the only thing that lasts when the foundation has failed. The mill-and-overlay work itself, the depth, the prep, and the bonding, is a placement topic. Here the rule is to read the base before deciding, because the base condition makes the call, not the look of the surface.

Asphalt vs concrete driveway

Asphalt and concrete both make a good driveway, and the choice is mostly cost, climate, and how you want to maintain it. Asphalt costs less up front, goes in fast, you can drive on it in days, and it flexes with the freeze-thaw of a cold climate instead of cracking, which is why it dominates driveways in the north. It is darker, so it melts snow faster, and it renews by sealcoating and eventually overlaying. The trade is that it needs that upkeep and it softens in extreme heat.

Concrete costs more up front and takes longer to cure before you can use it, commonly a week or more, but it lasts longer with less surface maintenance and holds up better to standing heavy or slow loads without rutting. It does not need sealcoating to survive, though sealing helps in freeze-thaw and against deicers. In a hot climate, or where the finished look is the priority, concrete is often the pick. In a cold climate on a budget, asphalt usually wins.

There is no universal right answer, and the deeper comparison is its own topic. For most cold-climate residential drives, asphalt is chosen for first cost, speed, and freeze-thaw tolerance, and the maintenance is the price of those. That trade is the whole decision in one line.

Common driveway failures and what causes them

Driveway failures mostly trace back to the same few causes, and reading the pattern tells you what went wrong underneath. The distress on top is the symptom. The base, the drainage, or the compaction is usually the cause.

Edge cracking and raveling come from an unsupported edge and water working under it. Alligator cracking, the interconnected pattern in the wheel paths, is fatigue from a weak or wet base flexing too far under load. Birdbaths and ponding, low spots that hold water, come from a surface that was not graded or compacted to drain, and they feed every other failure by keeping water on the mat. Rutting and shoving come from a mat that was under-compacted or too soft for the load. Reflective cracks tell you an overlay went over a base or a mat that was already failing.

Cold climates: freeze-thaw and frost

In a freezing climate, water in the base and subgrade is the enemy in two states, and the install has to account for it. Frost heave happens when a frost-susceptible soil, water, and freezing temperatures show up together: the soil draws water up as it freezes, ice lenses form and swell, and the driveway heaves. The thaw is worse, because the trapped water saturates the soil over still-frozen ground and the base goes soft right when the spring loads come on.

The defenses are the same ones that make a driveway last anywhere, done with more discipline. Keep frost-susceptible fines out of the base so it does not wick and hold water. Drain the base and slope the subgrade so there is less water to freeze. Build the section deep enough for the region, because frost depth and the required strategy are local, set by the soil and the local practice, and a section that works in a mild climate is thin for a hard winter.

Asphalt's flex is part of why it suits cold climates. It moves with the heave and the settle where a rigid slab cracks, and the dark surface sheds snow faster. The cold-climate driveway still lives or dies on drainage, though. Keep the water out of the base and the freeze-thaw has little to work on, which is the recurring lesson of the whole job in its winter form.

Light-commercial lots and site access drives

A light-commercial driveway or a site access drive is the same build as a residential one with the loads turned up, and the difference is where the trucks concentrate. A drive that only ever sees cars can run thin, but the moment delivery trucks, a dumpster pad, or a fire-lane requirement enters, the section has to carry real truck loads at the spots where they land. On a data center or industrial site, the access road and the equipment-haul routes carry point loads that dwarf anything a car puts down.

The move on a mixed-use site is to thicken where the trucks go and not everywhere. The car field gets its light section, and the truck entrance, the dumpster pad, and the loading approach get a thicker mat and a deeper base, or they go to concrete where the loads are slow and heavy and would shove asphalt. Paving a whole lot to one thickness, then watching the dumpster pad rut while the car field sits fine, is a common and expensive mistake. Sizing the section to the traffic is the pavement thickness design guide.

The base and drainage discipline only gets stricter as the loads grow. A soft spot a car would never find is exactly what a loaded truck punches through, and differential settlement that is a nuisance under a driveway is a real problem next to a building full of equipment. The heavier the use, the less room there is for the skipped proof roll or the thin lift.

What to document

A driveway install that nobody recorded is a job you cannot defend when something moves. The base and the subgrade get buried, so the record is the only evidence the section was built the way it was sold, and on a callback it is the difference between a defended job and a guess.

Capture the section as built and the steps that prove it: the subgrade prep and proof-roll result, the base material and compacted depth, the asphalt mix and compacted thickness, the grade and the drainage, and the edge treatment. Note the cure guidance given to the owner and the first-sealcoat timing. The table below is the spine of that record.

Common mistakes

• Skimping the aggregate base to save money, then losing the mat over a foundation that keeps moving.
• Paving on a wet or soft subgrade because the schedule was tight, burying the problem under the mat.
• Laying a thin mat over a bad base and calling thickness the fix when the base was the problem.
• Building no slope or the wrong slope, so water ponds and runs toward the house instead of away.
• Leaving the edges vertical and unsupported with no taper, backfill, or restraint, so they ravel and break.
• Quoting a compacted thickness and laying a loose one, so the rolled mat comes in thin.
• Rolling the mat after it has cooled out of the window, so it never reaches density.
• Driving or parking heavy, static, or turning loads on the driveway before it has cured.
• Sealcoating too early, before the asphalt has cured and released its oils.
• Overlaying a driveway that is failing from the base up, so the old cracks reflect through.

Field checklist

Standards and references

The governing documents on any given driveway are the local building or paving code, the project specification, and on engineered or commercial work the geotechnical report. They set the section thicknesses, the compaction targets, the slope minimums, and the material gradations, and where they differ from the general practice here, they win. Residential driveway permitting and slope rules in particular are local, so confirm the jurisdiction's requirements.

For residential and light-commercial guidance, the asphalt-paving associations are the practical references. The National Asphalt Pavement Association and the Asphalt Institute publish driveway and flexible-pavement guidance, and many state and regional asphalt pavement associations put out homeowner and contractor driveway specs with typical thicknesses and base depths. State DOT specifications and AASHTO cover the materials, the compaction, and the pavement design framework the heavier jobs draw from.

Treat the thicknesses, base depths, slopes, and cure and seal times in this guide as typical residential figures, not mandates. The real numbers come from the soil, the traffic, the climate, and the adopted local spec. A 2 to 3 in mat over 6 to 8 in of base at a 1 to 2 percent slope is a common starting point. Confirm it against the spec and the conditions before you build to it.

Units, terms, and conversions

Driveway work carries a few names and unit systems across the estimate, the spec, and the dirt, so the same idea reads differently on one job.

Asphalt thickness is given in inches in US practice and millimeters in metric, and the number that counts is compacted thickness, not loose. The aggregate base is in inches of compacted depth. Slope is given as a percentage, as a ratio, or as a fall per foot, where 1 percent is about 1/8 in per foot and 2 percent is about 1/4 in per foot. Asphalt itself goes by hot-mix asphalt (HMA), blacktop, or bituminous concrete. The aggregate base goes by crushed stone, road base, or dense-graded aggregate (DGA). Mix temperature is in degrees Fahrenheit in US practice and Celsius in metric.

Hot-mix asphalt (HMA)

Asphalt and aggregate mixed and laid hot, the standard driveway mat; also called blacktop or bituminous concrete

Aggregate base

The compacted crushed-stone layer under the asphalt that carries the load; also road base or DGA

Subgrade

The native soil the driveway rests on, proof rolled and prepared before building

Compacted thickness

The thickness of a layer after rolling, which is what a spec and a quote should mean

Sealcoat

A thin protective surface coat applied after curing; maintenance, not structure

Raveling

The surface shedding sand and stone, common at unsupported or under-compacted edges

Birdbath

A low spot in the surface that holds standing water after rain

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