Hidden cost is below ground

Q: WHAT comprises 'groundwork' in the construction of a house, and is it a major part of the overall budget?

A: Groundwork is basically everything executed up to ground level - all the digging out surrounding the building of a house, the laying down of your foundations and drainage facilities and subsequent backfilling of everything. That includes excavations necessary for foul and roof drainage.

It might include the preparation of entrances, the digging out and setting up of the septic tank and, most especially, the removal of earth before setting and pouring the foundations.