Asphalt Driveway Thickness

How Thick Should An Asphalt Driveway Be?

The absolute minimum thickness a residential asphalt driveway should be is 2″ inches after it’s been compacted. This means that once the asphalt rollers have finished compacting the new asphalt, it should measure 2″ inches thick.

This is very important when obtaining quotes from asphalt contractors. All proposals should specify, in writing, the thickness they’re quoting and clarifying whether that thickness is before or after compaction.

This is a simple yet effective way of making sure you’re getting the asphalt as thick as you need for your driveway and you get exactly what you’re paying for.

We cover the discussion of asphalt thickness in great detail in our popular video, “How To Install An Asphalt Driveway”.

The In Depth Answer

Very rarely are two asphalt driveways the same. Not all asphalt driveways can be lumped into one simple answer when it comes to the thickness.

How thick does your asphalt driveway need to be?

How thick an asphalt driveway should be depends on a couple of things.

The Type Of Traffic You Expect To Have Will Help Determine How Thick The Asphalt Should Be On Your Driveway

One driveway may have considerably more traffic and heavy vehicles like delivery trucks, RV’s, boats, propane delivery trucks and septic cleanout trucks, while another may just have one or two passenger vehicles each day.

In this case, the thickness of each asphalt driveway is different depending on what will be the most common type of use on your driveway.

The more traffic and the heavier the vehicles, the thicker the asphalt should be.

The Soil, Or The Subgrade In Which The Driveway Is Being Laid On Will Help Determine How Thick The Asphalt Should Be On Your Driveway

An asphalt driveway is only as good as the soil it’s laid on.

It doesn’t matter what the thickness is if the asphalt is installed on if the soil is too soft. If the subbase isn’t solid, the asphalt, regardless of the thickness, will not last as long as it potentially could.

On the other hand, if the soil is naturally solid, then the life of your asphalt driveway will likely be much longer.

Soils vary greatly around the country.

Some soil is very dense and hard, while some soil contain expansive clays, and other soils are sandy and soft.

Soil that is expansive and has clay in it, or sandy soil, should be excavated before installing the asphalt. A good, solid base material like limestone, road base, recycled concrete or recycled asphalt compacted well are very good subbase materials.

On the other hand, if the soil is very dense and solid either from previous installation of base or naturally occurring subgrade like decomposed granite or decomposed limestone, then it’s likely the asphalt can be laid directly on the soil.

The thickness of the asphalt is still important, but the concern of major cracking becomes much less.

The Asphalt Mix Design Can Help Determine How Thick The Asphalt Should Be On Your Driveway

There are basically two types of asphalt mixes, or grades, that are most commonly used when installing asphalt.

3/4″ inch mix and 1/2″ inch mix.

3/4″ inch asphalt mix is generally used when the final finish, or the appearance, of the asphalt is not or is less important. 3/4″ inch mix, if used as the top coat or top layer of asphalt, can be porous and rough looking in appearance once rolled and compacted, but is more durable than 1/2″ inch asphalt mix. The absolute minimum thickness for a base layer is still 2″ inches compacted thickness.

While this is not the ideal mix for the top layer, once the asphalt has cured on the surface, having the asphalt sealed can minimize the rough appearance.

1/2″ inch mix is most commonly used as a top layer or the “top coat” of an asphalt driveway as the appearance of the 1/2″ inch mix is much smoother. The only time the thickness of asphalt can or should be less than 2″ inches, is on a top coat or top layer. In this case, whether it be an overlay or a brand new driveway installed in layers or “lifts”, the thickness can be 1 1/2″ inches compacted. But it must be specified by the thickness after compaction.

1/2″ mix can be used as the base layer, but should be installed thicker to make up for the loss in durability. Again, the absolute minimum thickness for a base layer using 1/2″ inch asphalt mix is still 2″ inches compacted, but you may find that most reputable contractors will install 1/2″ inch mix, at 3″ inches compacted thickness.

How Can A Person Know For Certain How Thick The Asphalt Should Be?

There are two ways to determine how thick your asphalt driveway should be.

A) Hire An Engineer

One way to try and ensure the right thickness of asphalt for your soil type, is to hire a soils engineer to evaluate the soil and determine a pavement design for you. However, hiring an engineer is not cheap and can multiply the price of an asphalt driveway by two to three times!

However, unfortunately there’s no guarantee that hiring an engineer will be the solution you’re looking for. There’s is a caveat when it comes to hiring an engineer. Most engineers will not guarantee their design. This means that even if you pay them to design your driveway and it cracks or fails, they cannot be held responsible.

B) Obtain At Least 3 Estimates From Reputable Contractors To Compare

Reputable contractors in your area will know what the proper thickness the asphalt should be for your driveway. This is why we always recommend obtaining at minimum 3 estimates from reputable contractors that specialize in asphalt driveways. If you’re ready to get estimates, you can find an Asphalt Pro right here on All About Driveways.

Beware Of Asphalt Thickness Scams

Paving an asphalt driveway too thin is actually a common practice by unethical contractors in the asphalt business. The thickness of an asphalt driveway is actually the #1 most common way dishonest asphalt contractors can scam homeowners.

And the worst part about this scam? Most people don’t even realize they’ve actually been scammed until it’s too late and the contractor is long gone.

Watch this video and see why the thickness of asphalt is considered the #1 most common asphalt scam.

Enjoyed this video? You can watch more videos like this from my video series or by reading my eBook: 

The Asphalt Scam Playbook: How to Outsmart Dishonest Asphalt Paving Contractors and Protect Your Hard-Earned Money.

Get your FREE copy or learn more about the most common asphalt paving scams here.

Conclusion

Unfortunately, there’s no “right” answer that anyone can give you online when it comes to the thickness your asphalt driveway should be. The thickness must be determined by someone that can visit onsite, whether it be an engineer or reputable asphalt contractors in your area.

The thickness of your asphalt driveway is the most critical part of having a new asphalt driveway installed. Be sure and get the job done right the first time by selecting one of our certified asphalt driveway pros right here on All About Driveways. Find an Asphalt Paving Pro Now!