A base material is not always needed when constructing a new concrete driveway in Minnesota. If the subgrade is uniform and compactable, it is ideal for concrete placement. Below are examples of when a base material is needed:
In most cases the sub-grade or base is not visual at the time of the estimate so an evaluation of the sub-grade is done once the old driveway is removed. If the soil is poor and un-compactable, four to eight inches of the original poor sub-grade will need to be excavated and removed and a base material will be brought in and compacted. In this instance a change order will be drafted and signed by all parties prior to work proceeding.
In some instances the elevation of the driveway needs to be raised. Base material will be brought in and compacted. This is determined at the time of the estimate.
Enlarge or Extend
Many times new concrete driveways are extended to go along the side of the garage for additional parking and/or enlarged for ease of use. Base material may need to be brought in to enlage or extend the base.