Our contractor just installed a new A/C system and he built this platform outside our house for the new condensing unit. It looks like it is a 4" concrete slab sitting on top of brick "legs". Looks like he poured some sand under the bricks to help keep them from sinking into the earth.

I can't tell if this is acceptable or if I need to ask the contractor to make it more stable.

I did use a level and confirm that the platform and unit is level. Having the bricks on the bottom seems like it would let any water runoff flow under the unit without getting blocked by the platform which is a good thing.

But we are worried that as time goes by some of the bricks will sink and it will start slanting or something.

I'm looking for honest opinions on whether this platform is reasonable.

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  • 3
    should be fine if there's not a lot of hydraulic activity. You can also shim it over the years to keep it level if needed.
    – dandavis
    Commented Jul 25, 2018 at 18:39
  • 1
    Model number? Can't look up the manufacturer's installation instructions without that.
    – Dan D.
    Commented Jul 25, 2018 at 21:42

2 Answers 2


That upper pad is probably not concrete, it's more likely Styrofoam covered with a coating to make it LOOK like concrete. That Styrofoam is actually better in some ways because it doesn't degrade or crack as easily as concrete and it absorbs vibration, making the unit quieter. Some jurisdicions however do not allow the styrofoam pads to be in direct contact with earth, hence the bricks.


Typical job for a contractor that wants to cut costs/corners. Seriously, how much more effort/money would it have taken to buy several bags of quikrete, formed it, and poured concrete? Then there would be no question as to the pad's performance over the life of the unit (and probably future replacement units as well). The unit itself looks like a high SEER/costly unit. Why scrimp on the pad?

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