Question re driveway grade...

[schwarz633]

[IMG]Steep Driveways

See more funny pictures and videos at Fugly.[/IMG]

[Zeke]

The cars are getting lower. No way that drawing and a late model water pumper compare. Dottore, there are lots of Porsches called Carreras. What do you have?

21% grade is about 12 degrees. I have to think this is the case.

[Dottore]

Originally Posted by ckissick

Yes, you must mean 21 percent. 21 degrees is equivalent to 38%, and it can't possibly be that steep. I mean, that would be ridiculously steep. It better not be that steep. If it is, you are SOL.

I design driveways, and 20% is the max allowed. I've seen 25%, and that's pretty darn steep. 25% requires grooves in the concrete for traction. 38%? Wow. Did I mention that's ridiculously steep? The steepest hill in San Francisco is Filbert Street, at 31.5%.

How long is the driveway? Can you measure the vertical change across the horizontal distance? Percent slope is vertical divided by horizontal.

Thanks guys. The expertise here always blows me away.

I honestly don't know whether the thing is 21 degrees or 21 %. We spoke in terms of degrees — but this was in German etc and it may well be percent. I will clarify this asap.

Can I assume if we are actually talking percent, that I could live with this grade? Car is a stock 997S.

[Porsche-O-Phile]

Honestly I think that's a bit of a cop-out answer on the part of your architect but maybe it's different over there. Something like that which would have required such a steep driveway (whether 21 percent or 21 degrees, it's still awfully steep) should have been brought to your attention and discussed. I'm not saying he's at fault, but it's something that I'd have definitely brought up in discussions with the client to go over the design and confirm that everything was okay to proceed before going to bid or into construction.

You mentioned an underground garage so I'm assuming the driveway in question slopes towards the structure. Are there provisions to drain water, snow run-off, etc. before it all ends up cascading into the garage? Trench drain? Cross-slope of some sort? It'll be very disappointing to see lots of water flowing rapidly downhill into the storage bay for your 911 if this hasn't been accounted for.

I'm really curious to see how this turns out and to learn more of the details...

[red-beard]

It cannot be 21 degrees........That would be way too steep.

997 wheelbase is 92.5"

Porsche 997 - Wikipedia, the free encyclopedia



Heigth is 51.5" - Based on the lines I added, the clearance will be around 7.5"

You'll high center in the middle of the wheelbase, so 41.25 inches.

7.5"/41.25" = 16.2 % gradient. Even the 17% code would get you!

Yep, you'll high center with that bad boy. It might actually be worse, since I'm looking at the side. If anything hangs lower...

They might be able to make it steeper in the middle and more gradual at the ends...maybe...

[Rick Lee]

Don't Euro-spec cars still have much lower suspension than US-spec ones? Also, the German word for degree is Grad, which sounds a lot like our grade. I don't know the German word for grade as it pertains to slope. Is it also Grad?

[MFAFF]

D,

The actual angle of the ramp is not the issue that will prevent you from using it..

22 degrees is very steep..once the car is on it, it will cope. Getting onto is the problem..
A 997 Carrera will have lower approach and departure angles than the 3.2/ SC drawing... I don't have my data to hand for the 996.

The drawing.. if they are signed off should clearly show the ramp design... I'd imagine that somewhere there is a profile drawing that will tell you what's what.

I'd also suggest to your architect that compliance with public car parking standards is appropriate to a communal below grade parking area in a condo...or at least designing something that is fit for purpose (ie not requiring a Dakar spec car to get an out.)...

Hope the drawings let you have a better idea of the set up.

[MFAFF]

D,

Had a chat to one of my German colleagues...

'Grad' is the gradient... so likely to be 21%..
The ramp design shoudl be 'fit for purpose'... as Germany, being an EU nation needs to comply with EU regs and standards as well as its own...

You may also ask about the fire escape strategy for the car parking level.
Access ramps are able to be used as pedestrian fire escapes, if they gradient is accpetable (21% may not be), if this is the case then a dedicated stair from basement up to normal ground level/ outside shoudl be present...

Part of this is to inform you.. so being BS'd by anyone is mroe challenging..

M

[911-32]

Another thought, if you have sufficient width on the ramp and can take the transitions on the diagonal, you can live with a steeper transition. May not be enough but could help at the margins. A lot of us use the diagonal approach whenever we have to tackle driveways with steep kerbing or town/traffic planners curse of speed bumps. I even have to do this on my very innocent looking driveway where it dips down to meet the road.