Driveway Too Steep? Most Effective Solutions!

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How Steep Is Too Steep for a Driveway?

Driveway Too Steep? A slope greater than 12% is considered too steep for a driveway. Contractors will generally not build driveways with slopes greater than 12%.

Steep slopes are legally defined as hillsides having a slope of 15% or more. Some local building codes may permit a driveway to have a slope of up to 20%. Typically, for driveway slopes greater than 12.5% transition slopes are required.

Reference: Page 2 of LADBS Parking Design

How steep is too steep for a driveway depends on the following factors:

1. The maximum driveway slope permitted by the local building code. This can differ from location to location, so you must check for your specific location.
2. The maximum  driveway slope that the local contractor will build without asking for an unreasonable price.
3. The maximum driveway slope at which you will be comfortable with.

The slope in point 3 should be less than or equal to that in point 2 and that should be less than or equal to that in point 1.

Solutions if Driveway Too Steep?

Driveway too steep? You can make your driveway less steep even on a steep terrain by using one of the following techniques:

Lengthen the Driveway by Incorporating Curves

Slope is a measure of how much a driveway rises or falls for every 100’ length. So a driveway with a slope of 15% will rise 15’ for every 100’ of driveway length.

Say your garage is 20’ above the street level and 100’ away from the street. A straight driveway would mean that it will have a slope of 20%. This is clearly too steep. 

You should increase the driveway length to 200’ by building it in a curve rather than a straight line. The slope will now be a more manageable 10%. 

The assumption here is that you have enough land to build a longer curved driveway.

Build the Garage at a Level Different than the Main House

In case you do not have land to make the driveway longer than 100’, then an alternative is to build the garage at a level different from the main house. Let us go back to the earlier example. 

House that is Uphill

Build a basement garage if your house is uphill. A basement garage is exactly what it says. Both the basement and the garage are built below grade under the main house.

Now the garage floor is 10’ lower than the house floor and only 10’ above the street level. A 100’ long driveway from the street to the garage door will have a slope of 10%.

House that is Downhill

Build a garage with the floor at the same level as the 2nd floor of your house. The space below the garage could be a room or a covered porch.

Now the garage floor is 10’ above the 1st floor of the house floor and only 10’ below the street level. A 100’ long driveway from the street to the garage door will have a slope of 10%.

How Do You Prevent Erosion On A Steep Driveway?

Driveway too steep? Better take care of potential damage due to soil erosion.

Unless preventive action is taken, a steep driveway is more prone to erosion as compared to a flat driveway. This is natural as rainwater flows down with higher force due to gravity, taking soil and other debris with it.

Soil erosion can reduce the life of your driveway quite dramatically. It can also have a destructive impact on the surrounding landscape and neighborhood. 

The eroded soil not only ends up at the bottom of your driveway but also blocks up driveway and storm water drainage systems. This can even lead to flooding.

To prevent erosion of a steep driveway you have to consider the following factors:

• Steepness of the driveway
• Soil make up
• Driveway base preparation
• Driveway material
• Driveway Drainage System

A French Drain under driveway is a good way to improve drainage.

A few practical ways to prevent erosion of a steep driveway and the neighboring landscape are:

1. Building a terraced garden along the driveway
2. Plant shrubs or trees with deep roots
3. Grow grass on the driveway sides
4. Use sandbags to divert rainwater away from the driveway
5. Build retaining walls uphill
6. Use Geotextiles or Erosion Control Blankets

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