Establishing ‘relative grade’ is extremely important in the site work phase of new construction.

When ‘placing’ a structure on any lot the grade from the top of grade to the bottom of the ‘cut’ is critical. The cut must be figured from bottom of foundation wall, in caisson construction or bottom of footing. Wall height and the amount of foundation to be exposed above grade must be considered. The worst scenario is when the cut is made too deep. This usually will not allow for enough ‘fall’ away from the foundation to allow the surface water to run off. Great care should be taken to make sure the excavator knows and follows the established ‘sub-grade’.

On sloped lots the grading is equally important for the same reasons, but there are new factors to consider. First, is where the ‘walk-out’ or ‘garden-level’ grade is going to intersect the existing slope of the lot. The frost wall, which is below the grade at the lower slope must be adjusted to a depth where it can have the minimum of 3’ below grade without having to add too much fill. Too much fill creates and even steeper grade ‘below’ the structure.

Notice in this example that in order to keep the frost wall at 3’ below grade the wallabove grade has to be quite tall. The foundation steps are often set on site, so the adjacent grade can be examined to determine the best location for them.

Proper relative grade is the first step towards a properly constructed foundation. Good bench marks set by a surveyor and/or an experienced construction field supervisor are recommended for this important phase of construction.