Concrete Formwork Flashcards

What is the purpose of a hold-down anchor embedded in a concrete foundation for wood frame walls?

Answer: To resist uplift and overturning forces in shear walls by connecting the wood frame to the foundation

Hold-downs (or hold-down anchors) are structural connectors embedded in the concrete that bolt to the end posts of shear walls. They resist the uplift forces that wind and seismic loads generate at shear wall corners, preventing the wall from rotating off the foundation.

What is the purpose of a waterstop installed at a construction joint in a below-grade concrete wall?

Answer: To prevent water migration through the construction joint from the outside to the inside

Waterstops are strips of PVC, rubber, or metal embedded across construction joints in water-retaining or below-grade structures. They create a physical barrier that water cannot migrate through, sealing the joint against hydrostatic pressure from groundwater.

What is the minimum footing depth for residential construction in most of Canada's cold climate regions?

Answer: Below the frost line — typically 1.2 m to 2.0 m depending on the region

The NBC requires footings to be placed below the local frost depth to prevent frost heave from lifting and cracking the foundation. Frost depths in Canada range from about 1.2 m in southern regions to over 2.0 m in northern areas. Local codes specify the exact depth.

What is the purpose of rebar spacers (chairs or bolsters) when placing reinforcing steel in a footing form?

Answer: To maintain the specified concrete cover over the reinforcing steel

Chairs and bolsters hold the reinforcing steel at the correct height above the form bottom (or the ground for footings on grade), maintaining the specified concrete cover. Proper cover is essential for corrosion protection and fire resistance.

What is the maximum recommended spacing between internal vibrator insertions when consolidating concrete in a wall form?

Answer: 1.5 times the vibrator's radius of action (typically 450 mm for a 50 mm vibrator)

The vibrator should be inserted at intervals not exceeding 1.5 times its radius of action so that the zones of influence overlap and all concrete is consolidated. For a standard 50 mm vibrator with a 300 mm radius of action, this means insertions no more than 450 mm apart.

What is the purpose of a sill plate anchor bolt embedded in a concrete foundation wall?

Answer: To mechanically connect the wood sill plate to the concrete foundation, resisting shear and uplift

Anchor bolts are embedded in the concrete (or installed with epoxy) and project up through the sill plate. Nuts and washers secure the plate to the foundation. They resist shear forces (lateral loads trying to slide the wall off the foundation) and uplift forces.