Reinforcement and Embedded Items
Reinforcement and embedded items covers bar sizes and grades, cover, laps, supports, dowels, anchor bolts and the pre-pour inspection that catches errors before they are buried.
Core rules
- Metric bar designations give the nominal diameter in millimetres: 10M is 11.3 mm, 15M is 16.0, 20M is 19.5, 25M is 25.2, 30M is 29.9, 35M is 35.7.
- Grade 400W (weldable) is common; higher grades and epoxy coating appear where specified. Cut and bend per the bar list; never flame-cut or field-bend without approval.
- Cover depends on exposure class in the CSA A23.1 tables. Ground-contact slabs typically need about 75 mm where cast against earth; formed surfaces exposed to weather need less, so read the table for the project's class.
- Laps are taken from tables by bar size, grade and class, commonly expressed as a multiple of bar diameter. Chairs, bolsters and mesh supports hold the steel at the correct elevation; sagging steel is the most common defect.
- Dowels at movement joints are aligned, half debonded or sleeved. Embeds, sleeves and anchor bolts must be coordinated and held during the pour.
- Before the pour: steel clean of mud, oil and ice; correct size, spacing, lap and cover; embeds present and plumb.
Worked example
An 8 m by 12 m slab is reinforced with 15M at 300 mm on centre both ways. Bars running the 12 m direction are spaced across the 8 m width: 8,000 divided by 300 is 26.7, so 27 spaces, which means 28 bars at 12 m, or 336 m. Bars running the 8 m direction: 12,000 divided by 300 is 40 spaces, so 41 bars at 8 m, or 328 m. Total is 664 m before laps and waste; adding 5 percent gives about 700 m to order.
Traps
Dividing length by spacing and forgetting to add the extra bar: you count spaces, then add one. Omitting lap length from the takeoff. Walking the mesh down into the concrete. Cutting a bar to clear a sleeve without engineering approval.