In reinforced concrete construction, two types of rebar are commonly used: plain rebar (BjTP) and deformed or ribbed rebar (BjTS). These are not a matter of preference — each has a distinct structural role, and swapping one for the other can weaken your building.

The Fundamental Difference: Bond

Concrete and steel work together only if they move together. When concrete is placed in tension, that force has to transfer into the steel bar inside it. This transfer is called bond, and it is where the two bar types differ most.

Plain bar relies on surface friction alone. Deformed bar carries transverse ribs that mechanically key the bar into the concrete — much like the thread of a screw in timber. As a result, deformed bar can transfer far greater force before it slips.

Plain Rebar (BjTP)

Smooth surface with an even, round cross-section. Its defining property is that it bends readily without cracking, which suits elements that must be bent repeatedly.

Common grade: BjTP 280, with a minimum yield strength of 280 MPa. Typical uses:

  • Stirrups and ties — the binding rings around columns and beams
  • Distribution reinforcement in floor slabs
  • Shrinkage and temperature reinforcement
  • Light construction and non-structural elements

Common diameters: 8, 10, and 12 mm.

Deformed or Ribbed Rebar (BjTS)

Its surface carries transverse ribs whose height, spacing, and angle are governed by the standard. Those ribs are what deliver high bond strength to the concrete.

Available in grades BjTS 420, BjTS 520, and BjTS 550. Typical uses:

  • Main reinforcement in columns, beams, and foundations
  • All load-bearing structural elements
  • Multi-storey buildings, bridges, and infrastructure
  • Structures in earthquake-prone areas, at minimum BjTS 420, which meets ductility requirements

Common diameters: D10, D13, D16, D19, D22, and D25.

Comparison Table

Aspect Plain bar (BjTP) Deformed bar (BjTS)
Surface Smooth Transverse ribs
Bond to concrete Relies on friction Mechanically keyed
Grade BjTP 280 BjTS 420 / 520 / 550
Minimum yield strength 280 MPa 420–550 MPa
Ease of bending Easy Needs tools and a standard bend radius
Structural role Stirrups and distribution bars Main load-bearing reinforcement
Common diameters 8, 10, 12 mm D10 to D25

Both Types Weigh the Same

One point is often misunderstood: at the same diameter, plain and deformed bar have the same nominal weight. Weight is determined by diameter alone, following the SNI formula 0.006165 × d² per metre. The ribs on deformed bar are already accounted for in its nominal diameter.

So a 12-metre bar of 16 mm diameter weighs 18.94 kg whether it is plain or deformed. The full weight table for every diameter is in The Complete Guide to SNI Rebar.

Can One Substitute for the Other?

No, and this is not a matter of preference.

Plain bar as main reinforcement is dangerous. Its bond strength is far lower, so the bar can slip within the concrete before reaching its tensile capacity. The structure would fail at a load well below the engineer’s calculation.

Deformed bar as stirrups is technically possible and sometimes done, but it must be bent to the minimum radius the standard requires. Bending too tightly can crack the ribs and weaken the bar at precisely the point carrying the most stress.

The structural drawings decide. Substituting on site without the designer’s approval is a risk out of all proportion to the saving.

Make Sure Both Are SNI-Certified

Whichever type you use, make sure your rebar meets SNI 2052:2024: actual diameter matching the label, no reduced weight, and steel quality tested per batch. Check the raised marking on the bar, measure the diameter with a caliper, then weigh a full bar and compare against its nominal weight.

Frequently Asked Questions

What do BjTP and BjTS stand for?

BjTP is Baja Tulangan Polos (plain reinforcing bar); BjTS is Baja Tulangan Sirip (ribbed reinforcing bar). The number that follows is the minimum yield strength in megapascals.

Which is stronger, plain or deformed?

Deformed bar, on two counts at once: its yield strength is higher (420 MPa and above versus 280 MPa) and its bond to concrete is far better.

Do plain and deformed bar cost differently?

Per kilogram the difference is usually small, since higher-grade deformed bar passes through tighter process control. Because both weigh the same at a given diameter, the fairest price comparison is per kilogram.

For a two-storey house, which should I use?

Both. Deformed bar for main reinforcement in columns, beams, and foundations; plain bar for stirrups and slab distribution reinforcement. Grades and diameters follow the structural drawings.

Is deformed bar always better?

For main reinforcement, yes. For stirrups that must be bent tightly and repeatedly, plain bar is more practical and structurally sufficient.

SNI Rebar Direct from the Mill

Inter World Steel produces plain and deformed rebar certified to SNI 2052:2024 direct from our mill in Tangerang, backed by more than 50 years of manufacturing. Every bar is guaranteed for size, weight, and grade, and comes with full documentation. See our Product Specification or our Premium Rebar line.

Contact our team through the Order Now page to discuss your project requirements.