Parking Garage/Covered Parking Slopes

[runoff]

To all;

I have a quick question. I have a design that the architect presented to me. He has designed a hospital that will be raised and is in the form of the letter T. The parking underneath the top portion of that T I have been able to maintain 1.5% to 2.0% slope to catch basins. However the right side of that T at the base, has been a little tricky. The bare minimum slope that is available is 0.7% from the concrete to the paving and then 1.5% to a series of catch basins. In any of your experience, do you see that this 0.7% is a problem? Again it is going to be well covered and we might get some rain that is blown in but I doubt it will be that much and then carry over from cars driving underneath. Also, the other side of that T is well sloped at 1.5% or better.

What do you great guru's think?

Runoff

 

[LHA]

Poured concrete, screed finished or better at .007, then bituminous concrete at .015? There will be no problem draining either.

Engineering is the practice of the art of science - Steve

 

[dik]

If you have frost conditions and the garage is non-heated, then you should be looking for a minimum slope of 1-1/2% to minimize 'skating' areas. You may also have problems with tolerances in the pour leading to 'flat' areas.

Dik

 

[runoff]

I know but it will be impossible to get 1.5% inside this section of the garage. I had to come and reanalyze from the original engineers design. I am bareley getting 1.5 in some areas and bare minimum at a low portion of the parking is as low as 1.2%.

I agree with you on the skating portion. That is what I am really worried about. I liked the screed finish idea by Steve which will get the minor flows out of there. If it does flow to the other side, then there will be more of a slope in that area.

Runoff.

 

[nutbutter]

I've always gone with a bare minimum slope of 1.00-1.50% on asphalt (depending on the contractor) and a 0.5% slope on concrete.

If it's concrete and you have a nice finish on it, 0.7% shouldn't present any problems.

Some good contractor can lay asphalt at 1.00% for short stretches without creating "bird baths" or "skating areas", however, I think that is the exception more than the rule. I try to keep it at 1.50% in areas that will be seeing significant runoff.

Peace,
Stoddard

 

[dik]

I try to maintain the 1-1/2% just for liability reasons. I don't have my hands on it now, but I have a couple of articles on this as well as copies of various cities building by-laws regarding slopes.

Dik

 

[runoff]

Thanks everyone. With the agreement of the owner, contractor, architect and myself, we went ahead with the 1.2% design. The funny thing about it is that we are only talking about 2600 to 3000 square feet of parking area that we are worried about. I had the superintendent of the job out there and myself as the paving contractor layed the paving. He did an excellent job. We ended up getting 1.3%. The architect changed up his plans and the covered parking will have coverage of 24 to 26 feet with concrete paving at 0.5 to 0.65%. Not what I really wanted but it will work. I do not think any rain will get in there anyway.

Thanks again.