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Max Slope of Concrete Driveway

Max Slope of Concrete Driveway

Max Slope of Concrete Driveway

Hi Everyone,

A client has requested a driveway design requiring 30% - 35% slopes on a very steep tropical lot in Hawaii. The site is quite narrow and does not have enough space for switchbacks. The parcel does have an existing driveway at those grades (see photos).

The client and the architect are both pushing the steep slope design due to most driveways in the neighborhood being constructed this way. However, the local standard requires a max slope of 15% or less and most colleagues I've consulted would not exceed 20% due to liability issues. The issues I've identified include vehicle damage due to rapid slope transitions, lack of emergency vehicle access, drainage issues, the slopes exceeding local codes and sound engineering judgement.

My instinct is to decline the project but would appreciate advice on:

1. What is the upper limit for a driveway slope?
2. Is there a workable solution I'm not seeing here?

Hawaii PE

RE: Max Slope of Concrete Driveway

Car lift?


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Max Slope of Concrete Driveway

LittleInch (Petroleum)9 Feb 24 21:36
Car lift?

And a ski lift for guests?

RE: Max Slope of Concrete Driveway

1 in 8 might be a better slope with a transition at the top to keep from bottoming out. Need drainage slots and/or roughness to keep formation of ice or slippery rain from causing problems.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates


RE: Max Slope of Concrete Driveway

A garage below the main floor?

What is this slope?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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