Excavation

EXCAVATION

Before site layout can be performed, a site plan prepared by the municipality in accordance with the zoning status must be obtained.

Based on the dimensions given in this plan, a survey engineer determines one corner and the building line of the structure. The remaining corner points of the building are then established using a tape measure, and stakes are driven at the building corners.

The foundation pit is then excavated using excavation machinery.

DETERMINING THE EXCAVATION DEPTH

Buildings are generally assigned an elevation datum from the top of the curb stone (sidewalk level) of the widest road to which the building faces. If the sidewalk has not yet been constructed, the sidewalk level is taken as 0.18 m above the road surface. If the road has not yet been constructed, the top-of-curb elevation is determined by the municipality within 20 days at most, based on the project prepared for that road.

When assigning an elevation to a building, the highest sidewalk level at the midpoint of the road frontage from which the parcel takes its datum is accepted as the benchmark.

*** If there is a difference of 3.50 m or more between the corner elevations of the road frontage from which the parcel takes its datum, the building footprint is terraced and the elevation is determined by taking the top of the curb stone at the midpoint of each terrace as ±0.00. However, the height of each terrace measured from its own lowest curb stone must not exceed 1.75 m.

EXCAVATION DEPTH = (Storey Height + Foundation Bond Beam Height) − (Sidewalk Elevation + Ground Floor Elevation)

MEASURING THE DEPTH OF THE FOUNDATION PIT

Elevation transfer is carried out to measure the depth of the foundation pit.

First, the elevation is transferred from the road to a stake using a water-level hose or a surveyor's level. When using a water-level hose, the water level on the road side of a transparent hose filled with water and free of air bubbles is equalized with the water level on the stake side, thereby completing the elevation transfer. The elevation is then transferred in the same manner from the referenced stake to other stakes or fixed points such as walls or trees. A string line is stretched between the referenced points, and a steel tape measure attached between the string lines is used to measure the depth of the foundation pit.