How To Build A Driveway On A Steep Slope?

Gravity will make your work a lot harder when building a driveway on a steep slope. Materials like gravel and concrete just want to move downhill. Steep driveways can also have issues with drainage, traction and walkability. 

When building a steep driveway, you have to think carefully about the design of the driveway, what materials you’ll use and the best techniques for laying down the driveway. We discuss these and more in detail below. 

How Steep Can A Driveway Be?

The first thing to consider is how steep the driveway will be. Of course, this depends greatly on the slope of the ground where you want to build the driveway. 

The maximum gradient you can drive up safely is around 25%. And even that can be dangerous for certain vehicles to drive on. 

Generally, the recommended max gradient for a driveway is 12-15%. This slope is relatively easy for most vehicles to navigate. 

Anything beyond 15% comes with various risks such as vehicles sliding down especially when it snows. Some cars can also scrape their bottom on the slope. 

There may also be local regulations in your city or by your HOA that mandate the maximum slope of a driveway. 

If the area where you are building a driveway is under the recommended 12-15% gradient, then you can build a driveway going straight up from the road to the garage. 

If it’s steeper than that, you have to find ways to adjust the slope of the driveway such as adding curves to it. 

What’s The Best Material For A Steep Driveway?

You can build any type of driveway on a steep slope, whether it’s concrete, asphalt, paver, cobblestones, or gravel. 

There’s no one material that’s better than the other for a steep driveway – each has its pros and cons. 

Gravel, for instance, offers excellent traction on steep slopes. But it washes away easily and will gradually shift downhill. So it requires regular maintenance. 

Concrete doesn’t move once it sets, but it can be tricky to pour on a steep slope. Traction can also be an issue when it snows. 

Choose a material that fits your budget and gives your home the aesthetics you want. Then learn how to work with that material to build a steep driveway. 

How To Build A Concrete Driveway On A Steep Slope

Let’s start with one of the most popular types of driveways – concrete. 

A concrete driveway is great for steep slopes because it stays in place once it has cured. Even with heavy traffic and water runoff, it stays firm, though it may erode over time. 

The biggest challenge with building a concrete driveway on a steep slope is pouring it. The wet mixture will want to sag downwards. If it’s too wet, it can actually flow down the hill. 

That’s why contractors use a drier mixture when pouring concrete on steep slopes. How wet concrete is is called slump. Slump ranges from 1 inch (very dry) to 10 inches (very wet). 

For a typical driveway, a slump of 4 to 5 inches is common. But this can be too wet for a steep slope. 

For steep driveways, a concrete slump of 3-4 inches is recommended. It’s dry enough that it will not sag or shift downhill, but still wet enough that it’s easy to work with.  

Here are a few other tips. 

• It’s a good idea to use rebar or mesh to reinforce a steep concrete driveway. This will reduce the chances of cracking and other kinds of damage. 
• When pouring concrete, start at the lowest point going up. This helps keep the concrete in place as you spread it. 
• Make sure the concrete has a coarse finish to provide adequate traction. You can add coarse aggregates to the mixture to achieve this finish. 
• For very steep slopes, you may have to build the driveway in a curve or curves to reduce the gradient. Another option is to raise or lower the driveway (relative to the surrounding ground) to get the gradient you want. This may require building a retaining wall. 

Here’s a great video of a concrete driveway being built on a steep slope. 

How To Build A Gravel Driveway On A Steep Slope

A gravel driveway is a challenge both during and after installation. 

When building the driveway, you have to keep the gravel from rolling down the hill. Once the driveway is done, there is still a risk of the loose gravel shifting downhill especially from traffic and water runoff. 

The best solution I’ve seen is to use stabilizers to keep the gravel in place. These are sometimes called gravel or grid pavers. 

They are grids that you connect and lay on the ground or the base of the driveway. You then cover these grids with the gravel. 

The grids strengthen the driveway and, most importantly, keep the aggregates from rolling down the hill. You can have heavy rain or lots of traffic on the driveway and the gravel stays in place. 

Here’s a video of what the grids look like. There are many brands in the market, so do your research to pick the best one for your driveway.

You can certainly build a steep gravel driveway without using stabilizing grids. I recommend using angular gravel. These sharp stones shift less and will hold themselves in place. 

Drainage is also super important. You’ll need an aggressive crown to ensure water drains to the sides. You’ll also need additional drainage options like a swale or French drain to ensure rain and snow don’t wash off the gravel.

Be ready to re-gravel the driveway every 2-4 years. Thankfully, gravel is cheap so this isn’t a deal breaker for most homeowners. 

Here are some more tips for building a steep gravel driveway. 

• Make sure the driveway has a sturdy base that is at least 6” thick. You can layer the base with coarse gravel, crushed stone or some other aggregate. Compact the base every two inches. 
• To improve the stability of the gravel, use different sizes. Start with large gravel at the bottom, smaller gravel in the second layer, and finer gravel at the top. 
• If the driveway is very steep, you can raise or lower parts of the driveway to achieve a gentler gradient. This may require retaining walls.  

How To Build A Paver Driveway On A Steep Slope

Pavers are great for steep driveways. Like concrete, pavers don’t shift easily downhill and can hold up well to traffic and runoff. 

But it’s super important that you lay the pavers properly. This includes building a thick base and laying the pavers in the right pattern. 

A 6” base is ideal. You can use gravel for most of the base then put a layer of sand at the top. 

Then, starting from the bottom of the slope, lay the pavers in a tightly interlocking pattern such as 45 degree herringbone. This pattern ensures pavers don’t move. 

Compact the pavers and seal the joints with polymeric sand to really lock them in place. 

As with other types of driveways, drainage is very important. While the pavers might not wash away in the rain, the base materials underneath might, resulting in cracked and sunken pavers. 

Another thing to keep in mind is traction. Choose pavers with an extra-coarse to ensure you can easily drive and walk up the driveway in all seasons. 

How To Build An Asphalt Driveway On A Steep Slope

The same tips for building a steep concrete driveway also apply to an asphalt driveway. Asphalt and concrete are poured pretty much the same way.

Make sure the base is sturdy and water permeable, grade the driveway properly to ensure good drainage and plan how you’ll pour the asphalt to keep it from running downhill. 

In any case, most people have contractors install their asphalt driveway. It’s not that it’s difficult, but it requires heavy machinery that only contractors have and can operate. Hire the right contractors who have experience working on steep slopes. 

How Do You Drain A Steep Driveway?

Don’t assume that because the driveway is steep, you don’t have to worry about drainage. Water may not be pooling on the driveway, but it could be flooding the streets, your neighbor’s yard or another part of your home. 

Note that in some cities, you could get fined if runoff from your home ends up in the street. 

Heavy runoff on your driveway will also erode or wash away materials. 

For paver, asphalt and concrete driveways, channel drains that cut across the width of the driveway are a must-have. They collect water running off the driveway and drain it elsewhere.

For gravel driveways, build a swale or French drain to slow down and redirect water coming down the hill. 

One good thing about a gravel driveway is that it allows water to sink into the ground. So you won’t have as much runoff to deal with. 

But you can also build a permeable driveway using other materials. These days, it’s easy to find permeable or pervious asphalt, pavers and even concrete.