Formwork Flashcards

What is the main structural concern when designing formwork for a concrete slab?

Answer: Supporting the dead load of wet concrete and live loads during construction

Slab formwork must support the substantial dead load of wet concrete (approximately 24 kN/m³) plus construction live loads including workers, equipment, and material storage. Shoring and reshoring must be engineered accordingly.

What are walers (wales) in wall formwork systems?

Answer: Horizontal members that stiffen the form panels and distribute the pressure from ties

Walers are horizontal members (typically doubled 2×4s or steel channels) attached to the outside face of form panels. They stiffen the forms, distribute lateral concrete pressure, and provide attachment points for form ties and bracing.

What is the purpose of chamfer strips in formwork?

Answer: To create a bevelled edge on exposed concrete corners

Chamfer strips are triangular pieces of wood or plastic placed in the inside corners of formwork. They create a bevelled (angled) edge on the finished concrete, preventing sharp 90-degree corners that are prone to chipping and damage.

In cold weather concreting in Canada, what is the minimum concrete temperature at placement recommended by CSA A23.1?

Answer: 10°C

CSA A23.1 recommends a minimum concrete temperature of 10°C at the time of placement during cold weather conditions. Insulated forms, heated enclosures, or concrete blankets may be needed to maintain adequate curing temperatures.

What is the purpose of reshoring (backshoring) in multi-storey concrete construction?

Answer: To re-support previously stripped floors that haven't reached full design strength

Reshoring involves reinstalling temporary vertical supports under concrete floors that have been stripped of their original formwork but haven't yet achieved full design strength. This distributes construction loads from upper floors to lower levels.

What material is most commonly used for residential foundation formwork in Canada?

Answer: Plywood and dimensional lumber

Plywood (typically 19 mm or 3/4 inch form-grade) combined with dimensional lumber for studs, walers, and bracing is the most common formwork system for residential foundations in Canada due to its low cost and availability.