Parking Garage Question

[runoff]

To all;

I am looking for some guidance on weather I am just being hard headed. I am presently working on a medical center that will have a parking area under the building but will be kept to existing elevations. In other words the building will be raised and parking will be underneath. I have been going around and around with the architect and his designer about drainage for the parking area under the building. His designer wanted me to have the driveway coming into and through the parking raised with parking spaces sloped down from the drive. The curbing would have curb cuts and allow water to migrate away from the parking spaces but there is still risk of collection in the wrong places. This also in turn has the slope towards the foundation footings as well as the possibility of collecting at the building entrances. Our structural said he would not seal it the way they want it and told me to just put my foot down about it.

I informed the architect in a meeting yesterday that I would prefer having the slope of the parking go to a channeled center of the drive and convey the incidental water away from the area. This would allow flow from cars, rain that blows into the area and possible sheet flow from collecting in all the wrong places. I told them that I felt parking garages, especially with this design, should be sloped at least 1.0 to 1.5% to the catch basins. I felt like I was in the right but we basically left the meeting agreeing to disagree. I also said without being too direct that if they did not like it then they should possibly seek another engineer.

With what minimal information I have given you, do you think I am in the wrong?

Thanks in advance.

 

[francesca]

If they dictate a drainage design that undermines the integrity of the foundation, then who's going to lose their license? The architects or the engineers? It isn't the architects, so yes, you're right about putting your foot down, and so is the structural engineer.

 

[GeoPaveTraffic]

I agree with you, its just the right way to do it.

 

[TDAA]

Yes, it is your satamp on it. Your choice of what you accept.

Did the strucural speak out to the architect, or just go through you? If just to you, the strucural and the geotech should also provide thier opinions to the architect.

 

[civilperson]

A slope 0f 0.5% will be sufficient for smooth finished concrete pavement with some shelter from awnings or building overhang. This slope can vary in direction by using multiple inlets or grates, thus keeping the average grade level or close to it. To prevent birdbath ponds, outside the shelter of the building use 1.0% minimum for Portland cement concrete and 1.5 % minimum for asphatic pavement. Once again, multiple inlets can make the average pavement elevation approach level

 

[cvg]

it seems that you could do it the way the architect wants, but would require many more inlets and pipes. It would be much more expensive. Maybe if he understands that his method is much more expensive, and possibly less effective he will see the light. It seems that if you have a concrete floor with inlets at every low point and don't allow standing water, the drainage should not affect the foundations.

 

[runoff]

Thanks for the inpput. I looked at placing several catch basins and yard inlets to accomodate the architect but I know from experience the cost will go up substantially. The rain leaders from the roof will be coming down through the structure and then drop into my catch basins. Also, the covered parking is not all the way covered. The architect has designed the parking spaces on the outside perimeter to go out appoximately 4 to 5 feet beyond the coverage and therefore the rain volumes would come into the area and accumulate. It is for this reason that I want the slopes to be greater than 0.5%. I would prefer anything greater than 1.0%. Yes, the structural spoke to them today. Just another case of an architect thinking they know more than the engineer. Hope I do not offend any architects out there. Just venting. The structural could not convince them either. It is quite comical to say the least. So, I am going to give them two designs to choose from. One with almost 12 catch basins/yard drains around the parking and perimeter. Or 4 along the center of the garage with correct slopes. Any other ideas.

 

[dik]

I've been involved with about 30 or so parkades...

As long as you can get positive drainage from the front or to the drive isle, this should not be an issue. There should be no areas where water can accumulate. A minimum slope of 1-1/2% (1% in my opinion is not enough for drainage or to reduce areas where an ice hazard can form) should be maintained. In addition, your engineer should stipulate whatever sealing process should be used as well as how often this should be repeated. Should take special care at any expansion joints (good ones are costly). In additon, a schedule for hosing down the parkade should be established and hose bibs should be installed within the parkade.

Dik

 

[runoff]

Hey, thanks dik. Yea I have it designed at 1.5% with an outlined finish. I have also outlined cleaning schedule but I neglected the hosebib idea. Thanks I will make sure our mechaninal engineer has placed hose bibs in the parkade areas preferrable on either side of the entrance way.

Thanks

 

[fattdad]

Several comments: Being that the parking level will be under roof, there will be little direct rainfall - presumably the roof will direct the direct rain fall properly away from the building. The actual parking surface will be concrete and weatherproof (i.e., air-entrained as needed and not vulnerable to the element). When it rains, wet cars and incidental blow-in will dampen or maybe even make the pavement wet. However, if it was a building (i.e., rather than an open wall), that same amount of water would just hit the building and fall onto the ground adjacent to the building. So, there is nothing unique about the "amount" of water adjacent to the building as a result of this being a parking level. That said, it is proper to have the ground next to the building with positive drainage, whether it's a parking level or not. I think I'd argue against too much refinment to this design other than having the parking grade slope to the edge of the building to shed blow in and any water from the cars. Curb cuts, as needed would be a good idea and any trival water that needs to migrate through the curb cuts would presumable do what the water off the building will do (i.e., from the uppper levals) flow down hill.

Hope I'm on track and not missing something.

f-d

 

[runoff]

Thanks everyone for the comments. The city reviewed the first set of drawings and parking/traffic engineering rejected it. They stated that parkades must be sloped away from footings at all times unless impractal or cannot be designed that way. Then an alternate solution must be incorporated. They did not think there was enough evidence to design it the way the architect wanted and told him to have the engineer design towards the center of the parkade. "YES". You got to love those little sweet victories.

 

[TDAA]

Very nice.

Now when you are in the same position, you can back your argument with the city has rejected that design in the past.

 

[cvg]

hope you can now convince the architect that you need a change order to re-design it, since the plans were not approved...