Why Are Driveways Sloped? 2 Excellent & Interesting Reasons!

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Why Are Driveways Sloped?

Driveways are sloped primarily because your house & garage are not at the same level as the street. The driveway is often also intentionally sloped for better drainage. 

Residential driveways are sloped away to prevent flooding of the garage, house foundations and the house itself.

In very simple terms, your driveway is a private road leading that connects your house to the street. The most cost effective way is to do it in a straight line. This can result in a sloped driveway depending on the topography of your lot.

If your house is above the street level then the driveway will slope downwards from the house to the street. On the other hand, if your house is below the street level, the driveway will slope downwards from the street to the house.

A driveway that has a gentle slope is not a problem, especially if the slope is downwards from the house to the street. However, a steep driveway can pose several challenges as under:

• Difficult to drive and park on
• Unsafe for pedestrians especially when wet & slippery
• Difficult to control drainage
• May cause flooding if the slope is towards the house
• Increases risk of soil erosion under the driveway
• Can not use gravel as driveway material

If both your house and street are at the same level then your driveway could be level as well. However, a perfectly level driveway is not necessarily a great idea! 

Should a Driveway Be Level?

Even if your house and the street are at exactly the same height, your driveway should not be perfectly level. It is best to slope it slightly towards the street. 

The main advantage of a downward sloping driveway is that it provides natural drainage. The downpour from a rainstorm quickly finds its way to the storm water drains running along the street.

The risk of your garage, house foundations and the backyard getting flooded is largely mitigated.  Moreover, a driveway that slopes up towards the house looks more beautiful and enhances the curb appeal of your home.

What Is the Best Slope for a Driveway?

The best slope for our driveway is 2%, sloping down from the house to the street. That is a fall of 2’ for every 100’ of driveway length. 

Such a gradient is high enough to facilitate good drainage and yet not too high so as to make your driveway unsafe.

So even if your house is more or less at the same height as the street, try to build a driveway with a 2% slope towards the street. This is a good slope for houses in locations with moderate to heavy precipitation.

If you live in an area that is mostly dry and  has low levels of precipitation, then a downward slope of even 1% will be OK.

In addition to a sloped driveway using a Geotextile Fabric under Concrete also helps in improving the drainage.

Geotextiles facilitate drainage below the concrete driveway by permitting water to flow from the base and sub-base to the subgrade and be dissipated.

“The benefits derived from these three geotextile functions are most significant when subgrade soils are weak (California Bearing Ratio [CBR] <3)”.

STORMWATER

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The Best Geotextile Driveway Fabric for Your Driveway & Patio Base

Geotextile driveway fabric is a supportive layer that is laid between the compacted subgrade and the sub-base aggregates to prevent the migration and loss of the aggregates in to the subgrade. It helps stabilize the ground, permit drainage and prevent weed growth.

Here is the Geotextile Driveway Fabric I recommend.

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Cross Slope in Long Driveways

For long driveways, you should also incorporate a cross slope. A cross slope can be single sided or double sided. 

In a single sided cross slope, one of the sides is kept slightly lower than the opposite side. Some kind of drain or gutter runs along the lower side. Rainwater needs to just traverse the width of the driveway before it can get into the driveway drainage system.

In a double sided cross slope, both sides are kept slightly lower than the center. The driveway drainage system then runs along both sides of the driveway. This arrangement makes more sense for a wide driveway.

Thank you very much for reading this post. I do hope you found it informative and helpful.