Maximum Parking Lot Grades... 5

[jaengineering]

I have a challenging site fitting a new building & parking between two existing buildings. The best grade I can get on my parking lot grades is 6.5% to 6.9%. I normally use 5.0% as maximum grade in parking lots.

Anyone constructed ~6.9% slopes. How do they work now?

Thank you in advance for your help.
Best Regards
as

 

[Ron]

jaengineering...not sure where you are located, but if in the US, you have to contend with accessibility laws (Americans with Disabilities Act (ADA) and the resulting state requirements). With this consideration, the accessible portions of your parking lot cannot exceed 2%. That's often a problem and it costs money to correct it.

In general 6.9% is a bit high and will increase your liability as a designer. Work on ways to get it down....consider terraces in grassed areas or similar.

 

[CarlB]

7% slopes are tolerable, if aligned with vehicle. Can be dicey when icy.
Are retaining walls adjacent to buildings feasible to improve slopes?

 

[brandonbw]

The slope depends on what the local codes say. For somewhere like Los Angeles, you can look at page 3 here,

http://ladbs.org/LADBSWeb/LADBS_Forms/InformationBulletins/IB-P-ZC2002-001ParkingLotDesign.pdf

If you are dealing with ADA read through their book. You want to keep a 2% max in all directions on an ADA parking stall. There are also the max grade on the paths to the building to consider.

We just did one of these for a car service center and they wanted to use as much existing as possible. That turned out to be very tricky. And you do not want to get caught with the wrong design once the project is built.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

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http://bwstructuralengineer.com

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http://bwcivilengineer.com

 

[civilman72]

Another big issue is the car door... pushing the door open against a 7% grade can be difficult (i.e. for the elderly), and can be very cumbersome for anyone trying to carry something (say a kid in a car seat) while holding the door open with their rear end.

It may be acceptable to have a few stalls and drive aisles over a 5% grade, but you need to do something to avoid having the entire parking lot >5%.

 

[dik]

I think that Ron and Carl are being a bit kind... with 7%... I don't like going over 5%. 1:20 is the max handicapped slope in some jurisdictions.

In addition to ice issues as noted, you have to be careful of the grade and opening vehicle doors... even without a wind this can be challenging... either opening or closing the door can be a challenge.

Overall, it's a bad idea, and you should be looking at means of mitigating this slope.

Dik

 

[beej67]

Use more walls.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[dik]

beej... that's one tried and proven way...

Dik

 

[jaengineering]

Thanks to everyone for your responses. We moved the building around, added walls and were able to stay at 5% max slope. It's what I knew needed to be done. I appreciate the advice.

 

[dik]

I like your solution...

Dik

 

[brandonbw]

Care to share a little region of the before and after? Curious what the original design looks like compared to the retaining wall design. We may have to do something like this and the client was not aware that the existing handicap parking on a pretty steep slope isn't allowed.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

|

http://bwstructuralengineer.com

|

http://bwcivilengineer.com

 

[swazimatt]

I have posted this elsewhere, but figured the right people might already be watching this thread.

I am busy designing the platforms for parking and delivery to a new supermarket. I have searched all about the parking slopes etc and see that the consensus is to not exceed 10% on ramps which is fine, but the delivery area is parallel to a road that slopes at 2%.
The trucks will drive into the loading area with the grade, but to get all my levels to tie in (delivery and parking and FFL) i find that the loading apron will slope towards the road at between 7 and 7.5%. Will this be ok for a crossfall for delivery trucks? they will be moving downhill at 2% and across the bay at 7-7.5%

 

[TGLG]

If I am reading you right, swazimatt, you are saying that the 7% to 7.5% slope runs perpendicular to the axis of the truck.
If that is the case, given the width of a truck (about 8.5'), when the truck is sitting at the dock the back left corner will be about 7.5" higher (or lower) than the back right corner. This is not a generally a workable condition. Remember, they'll need to drive a forklift or pallet jack from the dock into the truck and back. If the tail of the truck is not level with the edge of the dock, that will not be possible.
You are probably going to need a retaining wall at one side of the loading berths.

Also, in general, it is best to have the loading berth pitch towards the building, rather than away (in other words, the tail of the truck is lower than the nose). That way, the truck is less likely to roll away from the dock when they drive the forklift onto the trailer.

Also watch out for sharp breaks in grade in truck access areas. If the break in grade is too severe, it is possible for the landing gear on a trailer to catch on the pavement. This can cause the landing gear to break and/or knock the trailer loose from the truck.