help: poured floor not enough elevation

[farnsworth]

building a garage with the help of my brother. trying to keep it cheap we mixed the concrete ourselves. and i ended up with the floor lying as low as the driveway concrete. although the dirt around the concrete floor sits about 2" lower, im still concerned that puddles might fill up around the concrete slab and seep into the garage floor.

so how high must a concrete slab be so that water cant get in? also i was thinking of correcting this by mixing a new batch of concrete and pour about 2 inches on top of the existing slab, or is it a bad idea?

 

[larry4406]

Typically, in new construction, a garage slab will pitch about 3" in the depth direction. Then the civil engineer will grade the exterior at a minimum of 2% (2 inches in 100 inches) to get water to pitch away. A 2% slope is extremely shallow and problematic if not deadnuts on with a hard surface (grass or gravel does not flow well at 2%). I would not use 2% if you have a choice.

Yes you can cap the slab with a new one. You will need to scarify the floor and apply a bonding agent and then pour. I think a 2" cap is too thin, we did 4" inches.

 

[logical]

Typically, in new construction, a garage slab will pitch about 3" in the depth direction. Then the civil engineer will grade the exterior at a minimum of 2% (2 inches in 100 ft) to get water to pitch away. A 2% slope is extremely shallow and problematic if not deadnuts on with a hard surface (grass or gravel does not flow well at 2%). I would not use 2% if you have a choice.

Yes you can cap the slab with a new one. You will need to scarify the floor and apply a bonding agent and then pour. I think a 2" cap is too thin, we did 4" inches.

2 inches in 100 feet is not 2%....you mean 2 inches in 100 inches or 2 feet in 100 feet if you really mean 2%.