403A Blueprint Reading

Question 1

On a Canadian construction blueprint, what does the abbreviation 'O.C.' stand for?

Accepted Answer

On centre

Answer

O.C. stands for 'on centre,' referring to the measurement from the centre of one framing member to the centre of the next. It is one of the most common abbreviations on construction blueprints.

Question 2

What type of line on a blueprint indicates a hidden or concealed feature below the surface?

Accepted Answer

Dashed line (hidden line)

Answer

Dashed lines (hidden lines) represent features that exist but are not visible from the viewing angle, such as footings below grade, beams above a ceiling, or pipes within a wall.

Question 3

On a floor plan drawn at a scale of 1:50, how long would a 5-metre wall appear on the drawing?

Accepted Answer

100 mm

Answer

At a scale of 1:50, every 1 mm on the drawing represents 50 mm in real life. A 5-metre (5000 mm) wall would appear as 5000 ÷ 50 = 100 mm on the drawing.

Question 4

What does a section view on a blueprint show?

Accepted Answer

An imaginary cut through the building to reveal interior construction

Answer

A section view shows what you would see if you sliced through the building along a cutting plane. It reveals wall assemblies, floor construction, foundation details, and vertical relationships between building elements.

Question 5

In Canadian blueprint conventions, what does the symbol of a triangle with a number inside typically represent?

Accepted Answer

An elevation reference or detail marker

Answer

A triangle with a number is commonly used as a detail marker or elevation reference. The number refers to a specific detail drawing or elevation view found on another sheet.

Red Seal Carpenter 403A Practice Test

Red Seal Carpenter 403A Practice Test

403A Blueprint Reading