We live in Northern Illinois (-20F in Winter + 1-2 ft snow to 100F summer) and have two a/c units which are now 30 years old and it is time to replace them.
They are located on the north side of our house which also has all of our neighbor's yard sloping toward it and we have continued to have water leakage into our basement from this in spite of draining all our gutters away from the house.
The current ac units sit on plastic footings set in a bed of gravel, problematic both because this conducts water to the nearby window well and because we end up having to "re-level" them every year. We are not sure if the gravel shifts, or the soil below it is settling, or what. We also have/had a sidewalk next to it which has settled/moved at least 1-2 inches over the 12 years we've lived here (due to those same water issues and/or chipmunks).
When we replace the units we are planning to get rid of the current gravel bed and replace that area with clay to try to reduce water infiltration to that side of the house and the nearby window well which results in basement leakage when we have hard rains (3" in a day).
What is the best solution for new A/C mounting?
- Minimal/easy maintenance (re-leveling)
- Quiet (AC units are right outside the home office)
- Water handling (allow water to run AWAY from the house, not act as a water reservoir right next to our house like the current gravel bed)
We've looked at the following options but aren't sure which is best:
1. Pour a new concrete pad
Pros: should be durable
Cons: May be expensive, hard to do, (and/or hard to find contractor to do) and if it still tilts/sinks (which we've seen with both the sidewalk and our driveway) may be expensive/hard to fix. Suggested methods would probably disturb soil and might add to water infiltration to basement.
2. Plastic pad
Pros: Cheap, light, easy install, seems to be favored by contractors
Cons: Not sure how durable these are - seems like it would be hard to replace if expected life is 10-15 years and it goes before we next intend to replace the AC units (which might be another 30 years). Also, may still tilt/sink if the soil below it moves and it's not clear how we'd fix the tilt.
3. Mount on wall of house
Pros: Should eliminate the possibility of tilting/moving
Cons: Not sure if allowed by code in Northern Illinois; Might be noisier since connected to house (but maybe there's a way to prevent noise transmission?); Not sure where to find materials to do or if contractors will be willing/competent to do it.