Slab retrofit - original pour not slopped properly

[benwr]

We (my work) recently had a building constructed that includes a 3 bay garage. I was not involved in the construction as it was not for our department. The construction was completed with some deficiencies and our department was brought on to help resolve the outstanding issues (how nice of them ha ha).

The major issue is that the concrete slab was not graded properly and when the workers are washing vehicles, water is not flowing towards the drains in some areas (some flows towards the rear storage rooms etc).

We had the contractor grind down parts of the slab to encourage proper drainage, but it was not sufficient. The firm that designed the building has come up with a plan to retrofit the slab, and it involves:

-Mechanically scabble 25mm (1”) off of the existing surface.
-Add new concrete on top of existing with slopes to drains ranging from 1.5%-3.5%

The thickness of the new concrete will vary, but my concern is that at the lowest points the top coat will be 1”. I feel that 2” would be more appropriate for a floor, especially one that will have vehicles constantly driving and parking on it. However, taking 2” of concrete off of the existing slab will be a major challenge for the contractor in my opinion (1” may present a challenge).

Just looking for some thoughts, ultimately the engineer in charge of the retrofit is the one with the experience on the job, but as a representative for the owner of the building, it is important to be comfortable with the plan.

 

[msquared48]

I wonder how the water drainage that goes to the storage rooms will be diverted to a drain with only a 2" cut-down of the slab. At the best case, the drain would have to be within 16 feet of the rooms for a 1 percent slope - the minimum for decent drainage.

Also, if you have to remove 2" in the area of the storage rooms, and leave it with no topping as I envision, this will decrease the thickness of the slab, severly weakening it.

Do I have the correct picture here?

Depending on the topping used, you can get away with 1", but 2" would be better, I agree.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[benwr]

The floor in the storage rooms is not being touched. The storage room doors will be adjusted as needed due to the floor being raised. This will also result in a downward ramp into these room areas. The entrance to the garage door openings will require a slight upward ramp as well.

Thanks for the response.

What type off topping came to mind when you though of the job?

 

[benwr]

also is it common to but wiremesh in the top coat, if it is 2" plus?

 

[benwr]

This has been resolved. thnanks for any input