Constructs Footing, Formwork, and Installs Piles

Chapter C1 – Constructs Footing Formwork and Install Piles

The National Occupational Analysis (NOA) for Carpenter (2013) identifies the required competencies (skills) for the task of constructing footing formworks and piles.

Key Competencies (NOA, p. 36)

1. Select materials according to site-specific requirements such as soil conditions and size of footing
2. Place formwork and ensure components are plumb, level, square and accessible for steel reinforcement and finishing work
3. Use benchmarks to determine elevations of footing in the excavation using tools such as laser levels, builders’ levels and string lines off batter boards
4. Place bracing to maintain square, straight and level footing
5. Brace step footings to maintain plumb, square and level, and to prevent blowouts
6. Build footing steps according to drawings and building code requirements
7. Install required components such as keyways, water stops, templates, bulkheads and miscellaneous inserts
8. Fasten components using fasteners such as duplex nails and threaded rods for ease of dismantling
9. Inspect assembled formwork to ensure it is straight, square and level, and that it is adequately braced and correctly measured

Foundation construction includes the excavation, setting of formwork, such as piles and footings as well as the placing and finishing of concrete. The carpenter is responsible for a lot of this work even if they do not physically complete tasks such as surveying and excavation.

Topic 1 – Excavation and Footing Forms

It is important to ensure the excavation is to the proper depth as well as provide room for the work that needs to be done below grade. Soil type will be a determining factor in how much the banks of the excavation will be sloped.

Footings will distribute the load of the structure it supports to the area below. The type of footing is determined by its purpose and may be continuous, independent or a floating slab. Continuous footings may be stepped for changes in elevation or widened to create a pilaster. Footings can be made from various materials such as dimensional lumber, plywood, manufactured or trench poured. Reinforcement (rebar) is placed in footings and pads to control shrinkage and provide tensile strength to the foundation. A keyway will provide a stronger connection point between the footing and foundation wall to resist lateral pressure and improve watertightness.

Source: http://r3construction.ca/

For additional information:

Review reading assignment LO 1 LS 1 Reading Assignment 1.2, LO1 LS 2 Reading Assignment 2.1

• Principles and Practices of Commercial Construction, study sections on “Foundations, Formwork (Footing Formwork)
• Carpentry, study section on “Footing Forms” up to section “Forms for Slabs”
• Canadian Wood-Frame House Construction, in the chapter titled “Footings, Foundations, and Slabs” read all information beginning at the section “Footings” up to but not including the section “Foundations”
• National Building Code of Canada, refer to “Footings and Foundations”

Review Instruction Sheet (IS) on Brightspace:

FNDT 100-120:

• IS 1.1 Excavations – Residential
• IS 2.2 Types of Footing
• IS 2.3 Footing Forms

Review Questions

1. Where should excavated material be stored?
2. From the NBC, what is the minimum depth of foundations in clay soils (good drainage) containing a heated basement?
3. What is the minimum depth of a foundation in well-drained clay soils containing an unheated crawlspace?
4. Backfill that is within 600 mm of a foundation shall be free of what?
5. What is the minimum amount a foundation must extend above finished grade?
6. True or False:

1. Excavations should be kept free of standing water
2. The bottom of excavations should be kept from freezing throughout the construction period

7. Describe a battered (tapered, pyramid) footing.
8. What is the purpose of a spread footing under a foundation wall?
9. In un-reinforced footings, the projection of a footing beyond the supported element should not exceed: ______________________
10. When using step footings

1. The maximum height of each step is:
2. The minimum length of each step is:
3. The thickness of the vertical connection must be:

11. What is the minimum thickness of footings allowed for in the NBC?
12. What is the minimum width of footings under an exterior basement wall supporting one floor?
13. What is the minimum area of a column footing? (columns spaced 3 m O.C.)
14. If the footings rest on gravel, sand, silt, or clay and there is a high-water table present, the footing width should be: _________________________
15. If brick veneer is added to the front of the house, what must be done to the footing under the brick?
16. Concrete for unreinforced footings must have a compressive strength of:
17. Two methods of anchoring a foundation wall to a footing are: ________________________
18. Which footing forms are usually installed first: inside or out? Why?
19. Explain the “key”

Topic2 – Layout and Install Piles

Deeper foundations will require more than a footing resting on soil to support larger structures or if the building is constructed where poorer soil conditions exist. In these cases, piles may support the rest of the foundation to a stable bearing area below the frost line. Piles are classified in many ways including material, how they are placed or how they transfer load. Soil movement can displace piles causing the foundation to shift. End bearing and friction piles are designed to eliminate movement.

Review:

Instruction Sheet (IS) on Brightspace:

FNDT 100-120 (p. 26-27):

• IS 1.2 Types of Piles

Text:

• Principles and Practices of Commercial Construction, Chapter 5 – Foundations

Review Questions

1. Name the materials piles are constructed from.
2. Loads are transferred to the soil from the pile by:
3. Name some advantages of using piles instead of footings.
4. What are sheet piles used for?
5. Describe the difference between a pile shoe and a pile ring.
6. What are wood piles treated with to prevent decay?
7. Name two types of concrete piles.
8. How are precast concrete piles installed?
9. Describe a bored caisson.

Topic 3 – Perform Takeoff for Footings and Piles

Determining the amount of material needed for footings and piles relies mainly on calculating the basic data. Perimeter and center line length are essential in calculating many material calculations such as:

Basic information for piles includes size (depth and diameter) and number of piles to determine:

Review Instruction Sheet (IS) on Brightspace:

PROJ 402 (p. 15 – 22):

• IS 2.2 Wall Footings
• IS 2.4 Pilings and Round Columns

Review Questions – 8.01.3

1. Find the center line length for the following footings:

1. Outside dimensions of footing 20’-6” x 34’-8”, footing 18” wide.
2. Outside dimensions of footing 14.5 m x 22.6 m, footing 450 mm wide.

2. Calculate the amount of concrete required (in yd³) for a footing 16” wide x 8” thick and outside dimensions of 24’ x 36’. Add 5% for waste, round up to nearest ¼ (0.25) yard³.
3. Calculate the amount of concrete required (in m³) for the following footings:

4. Calculate the amount of concrete required, in yd³, for 10 piles 14” wide and 18’ deep. Add 5% for waste and round up to nearest yd³.
5. How many cubic meters of concrete is required for 22 piles with a diameter of 600 mm and 9000 mm deep? Add 5% for waste and round up to nearest m³.