Topic 3 – Site Investigation and Building Layout with Hand Tools

Site investigation is a two-stage process consisting of a surface evaluation and a subsurface investigation. The surface elevation will provide information to the builder on site conditions such as how level the area is and if materials like rock or soil need to be added or removed. The subsurface investigation is important to determine if the conditions below the surface will support the structure being built. Soil samples are taken to determine bearing strength and shear capacity of the soil. Knowing the bearing and shear capacity is important. A low bearing capacity may require deeper or larger piles or a different type of foundation altogether. Determining the level of groundwater and level of frost penetration can be determined as part of the subsurface investigation. Compaction testing will determine if the surface supports foundations, sidewalks, roadways and parking lots.

Other important factors in a site investigation are:

1) site access

2) utilities and services

3) site safety and local bylaws.

Building Layout

The dimensions and location of a building are laid out from the property corners marked by the surveyor and referenced on the plot plan. Typically, we establish the front of the building line first. From there the main corners are staked and offsets (wings and additions) are located from the main building. Layout of irregular shaped buildings can also be done by staking out a larger rectangle and locating additional building locations by measuring along the length and width of the rectangle.

One method to ensure the corners are square is to apply the Pythagorean theorem (3-4-5 method). Square or rectangular layouts can also be verified by checking dimensions and the diagonal measurement are the same.

Batter Boards

Building layout often occurs before excavation is done. Batter boards are used to run stringlines so that the layout can be transferred to the bottom of the excavation and re-staked. Batter boards are located well outside the excavation, so they are not disturbed during excavation and allow room for equipment.

For more details, review Instruction Sheet (IS) on Brightspace:

CNST 102/126 (P. 66 – 70):

IS 3.2 Constructing Batter Boards

IS 3.3 Setbacks and Restrictions for Buildings

For further information and diagrams, review in texts:

Principles and Practices of Commercial Construction – Chapter 1

Carpentry, Chapter 28 – Laying Out Foundation Lines

Review Questions

What may happen to a house foundation resting on moist fine-grained soil (clay) if freezing takes place under the footings?

True or False:

Coarse grained soils under footings are more stable than fine soils.

Wet, coarse-grained soil will heave more than fine grained soil.

Soil testing may be done by auger borings, test pits, or checking nearby excavations.

Dry soils have a greater bearing capacity than wet soils.

Fine sands expand more than clays when wet.

Which building line is located first?

Explain three methods used to square the side building line off the front building line.

What is the diagonal measurement of a building 32’ x 42’?

What is the name of the horizontal members of batter boards and what height are they usually fastened to?

Batter boards should be kept a minimum of _____ outside the building lines.