Multi-storey parking rehab - drainage slopes

[LexW.]

Hi, I'm currently working on the complete rehab of a 3 storey underground parking strucure in Canada that was built in 1970. The reason for the rehab is due to poor initial drainage (almost none). Over the years of being exposed to de-icing salt, the concrete is generally delaminated, the rebars ae heavily corroded, etc.

Since we're repouring new slabs, I'm wondering about the drainage slopes. The latest edition of the CSA S413 requires a minimum of 1.5% with a preferable 2% slope. Given the limited ceiling heights that I have (2-2.1m) I want to limit the elevations at the high points without having to add a ton of floor drains. Knowing the CSA S413 applies to new construction, is there a way I can justify 1% slopes since we're dealing with a rehab?

Thanks!

 

[RobertHale]

I'm not familiar with the Canadian code, but if I were going to try to justify it, I would calculate a reasonable rain load based on the drain sizes and locations. I would also specify a good surface coating. I would also have a very serious discussion with the owner about a heightened level of maintenance required regarding joints and coatings. Then, the big thing will be convincing the code official that you have ameliorated any consequences of reducing the slopes from the code-stated minimum. I think you would need a solid plan for what you will do, and then you need to have a conversation with the AHJ explaining that plan. They may tell you to pound sand.

 

[dik]

One of the important things about parkade design is the proper drainage. Slopes are paramount. It was nearly a standard with RJC going back 50 years that 1-1/2 slopes were the minimum.