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Steel Reinforcement Bars: Key Information about Rebar Sizes

A reinforcing bar, also known as rebar, reinforces concrete in building work. 

Choosing the right rebar for your project requires a certain amount of knowledge and skill. The size of the reinforcing bar can vary greatly, but it will always be thicker than other types of metal.

When it comes to the steel bar, the part that makes it strong is the concrete’s ‘spine’. There are three different kinds of reinforcing bars, each stronger than the last. The size of the rebar will vary, but it will always be bigger and thicker than other types of metal.

Quality Control

Things to take into account when buying rebar include quality and size. Thankfully, there are global standards for rebar manufacturing to have consistency and safety in place. Concrete in itself is crucial for construction, supporting the likes of:

  • Allowing light to pass
  • Allowing water to pass
  • Building
  • Temperature insulation

The composition of concrete is what dictates its strength. When strength is necessary, that should become one of the main considerations for design. 

Size Variety

There’s structural integrity with rebar in concrete. However, the compression strength that concrete material has generally has the trade-off of tensile strength. It’s extremes on either end: high compression strength means little to no tensile strength. When there’s no reinforcement in place, concrete’s weakness is clear when it’s brittle or fragile.

  • Domestic, Small Scale Projects – 6mm, 8mm and 10mm rebar diameters will do the job. Patios and driveways do well with the lightest (6mm) option. Tensile stress levels then become minimal since the loads are. 8mm or bigger is ideal for columns, piers and walls. On the other hand, foundations and building footings are suitable for 10mm rebar.
  • Civil Engineering, Large Scale Projects – Tunnel or bridge construction do best when the rebar is a higher diameter. 

The installation of the right-sized rebar is critical for the overall project’s success. When installing flat slabs, such as pour-in-place concrete floors, use ⅜ inch rebar with a grid spacing of one foot. In most applications, a spacing of one foot is sufficient. For other flat slabs, like concrete driveways and patios, use a half-inch rebar with a spacing of approximately 3 feet.

It’s essential to ensure that the rebar conforms to standards both nationally and worldwide. Take these into consideration:

Rebar steel quality

Proper mechanical testing is the best way to produce the rebar to have quality and authenticity assessed. That way, rebar can have published specifications met for sure. Categories for components to test include, but are not limited to:

  • Compression
  • Fatigue
  • Malleability/Bending
  • Tensile strength

Yield strength

This measurement indicates steel’s overall strength. Heavy-duty rebar works well for high yield steel with grade 500 reinforcement.


Steel reinforcement bars are beneficial for construction; as such, rebar sizes have to be considered. Rebar quality and size need to be held to national and international standards. Consider the rebar yield strength alongside the steel’s quality.

Do you need a structural steel and fabrication specialist on the Sunshine Coast? Reach out to Phoenix Reinforcing today! We specialise in building products, reinforcing productions and cage fabrication, reinforcing sales, builder and concreter’s hand tools, and so much more.

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