After maybe a week of temperatures continuously below freezing, day and
night, my driveway raises well above the level of the garage's concrete.
The baking soda box is 2" high. The edge of the blacktop closest to the
box is raised about 1.5"; about a foot further from the garage, the
blacktop is maybe 2" high.
The house is on a slab. Soil in central NJ is somewhat heavy, but not
clay-like. The whole property slopes gently down toward the street,
which is 100 feet away. (According to Google Earth, the street end of
the driveway is 3 feet lower than the garage end.) Behind the garage is
a utility room. A little far-fetched that the water under the blacktop
gets there by seeping from the back yard under the 28' slab to the start
of the blacktop.
I have two good gutters taking roof water away from the blacktop. Each
discharges its water at least 12 feet from the sides of the blacktop.
One discharges its water about 25 feet closer to the street; the other
discharges about where the blacktop meets the garage, but as I said 12
feet to one side.
The driveway is 10 years old. The old one, which was completely ripped
out down to bare soil, also showed the same cold-weather behavior.
Even though it's only a cosmetic problem, and the blacktop will be level
with the concrete once the weather warms, any ideas how to prevent this
seasonal rise and fall?