What is a TMT bar?
A TMT (Thermo-Mechanically Treated) bar is a steel reinforcement bar that is rolled hot and then quenched with water. The outer layer cools fast and forms a hard skin. The core cools more slowly and stays tough and ductile.
That hard outer layer over a ductile core is what makes TMT the standard for houses. It grips the concrete well and bends on site without cracking.
TMT vs cold-twisted bars
- TMT bars get their strength from heat treatment. They keep a ductile core, so they bend well and absorb energy before they break.
- Cold-twisted (CTD) bars get their strength by twisting a ribbed bar cold. The twisting uses up much of the ductility, so the bar fails more suddenly.
For a house that has to stand for decades and ride out settling, wind and the odd tremor, TMT is the steel to specify.
TMT bar grades for a house
All RD TMT bars are made to IS 1786:2008 and carry the ISI mark under BIS licence CM/L-6200193709. We make three grades.
| Grade | Yield min | Elongation min | UTS/YS | For a house |
|---|---|---|---|---|
| Fe 500 | 500 N/mm² | 12% | ≥ 1.08 | The standard grade for most houses |
| Fe 550 | 550 N/mm² | 10% | ≥ 1.06 | Heavier, commercial and government work |
| Fe 550D | 550 N/mm² | 14.5% | ≥ 1.08 | Where the engineer asks for a ductile grade |
Which grade for which part of a house
- Slabs, beams, columns and footings in a normal house: Fe 500. It covers the great majority of residential work. See Fe 500 TMT bars.
- A house in a higher seismic zone, or a drawing that calls for a ductile grade: Fe 550D. See Fe 550D TMT bars.
- Fe 550 is for heavier commercial and infrastructure work, not a typical house.
If the drawing says Fe 500, buy Fe 500. If the engineer calls for ductility, buy Fe 550D. Our team will confirm the grade fits your drawing before the steel is loaded.
TMT bar sizes and uses in a house
We supply all seven sizes in 12 m standard length. The size for each element comes from the structural drawing.
| Size | Weight per metre | Typical use |
|---|---|---|
| 8 mm | 0.395 kg/m | Ties and stirrups |
| 10 mm | 0.617 kg/m | Slabs |
| 12 mm | 0.888 kg/m | Slabs and beams |
| 16 mm | 1.580 kg/m | Beams and columns |
| 20 mm | 2.470 kg/m | Columns |
| 25 mm | 3.850 kg/m | Footings and heavy columns |
| 32 mm | 6.310 kg/m | Heavy footings and columns |
As a general guide: 8 mm for ties and stirrups, 10 to 12 mm for slabs, 16 mm for beams and lighter columns, and 20 mm and above for heavier columns and footings.
How to tell good TMT bars from bad
This is where a home builder loses the most money. Not in the price per kilo, but in substandard steel.
The ISI mark and the test certificate
Genuine bars carry the ISI mark and the maker’s name on the bar. Every RD TMT dispatch also carries a NABL lab test certificate traced to the heat number on the bundle tag, so you can match the bars on site to the lab results.
If a bar has no ISI mark, or the supplier cannot give you a test certificate for the heat you are buying, walk away.
The bend test
IS 1786:2008 requires a bend and rebend test in every size. A genuine TMT bar bends to the set angle without cracking on the outer surface. It is the simplest check on site: bend a piece and look at the outside of the bend.
- NABL lab accreditation
- NABLT0826KA18884
- BIS licence, IS 1786
- CM/L-6200193709
- On every dispatch
- Heat number to test certificate
How much TMT steel does a house need?
A common rough guide for an RCC framed house is 3.5 to 4.5 kg of steel per square foot of built-up area. On that guide a 1,000 sq ft house uses about 3.5 to 4.5 tonnes, and a 2,000 sq ft house about 7 to 9 tonnes. The real figure moves with the number of floors, the spans, the soil and the seismic zone.
- 1,000 sq ft house
- 3.5–4.5 t
- 2,000 sq ft house
- 7–9 t
- Rough guide
- 3.5–4.5 kg/sq ft
The quantity you order comes from your structural engineer’s bar bending schedule. Buy to the schedule, and keep the dispatch notes so you can match what you bought against what the design calls for.
Where TMT bars are used in a house
Foundation and footings
The foundation carries the whole house to the ground. Heavier bars, 16 mm to 25 mm and more, go into the footings and the plinth beam. A weak foundation is the one failure you cannot fix later.
Slabs, beams and columns
Slabs use 10 to 12 mm bars in a mesh. Beams and columns use 16 mm and above, held by 8 mm ties and stirrups. This is the main body of the structure and most of the tonnage.
Lintels, stairs and openings
Lintels above doors and windows, staircases and the steel around openings use 10 to 16 mm bars plus ties. Smaller in quantity, but still the grade on the drawing.
Buying TMT bars for a house in Bengaluru and Karnataka
RD TMT supplies home builders, residential contractors and dealers across Karnataka and South India from our plant at Somanahalli, Mandya, with our registered office in HSR Layout, Bengaluru.
- Approved by BDA
- The Bangalore Development Authority has approved RD TMT Fe 550 and Fe 550D bars for its housing projects.
- Priced to your schedule
- Send your bar bending schedule and we price it by size and weight within one business day.
Price depends on size, quantity and the current market rate. See the projects we supply, or contact our team for a quote for your house.
A simple TMT bar checklist for home builders
Before the steel goes into the structure, check these six things.
- Check the grade on the tag.
The bundle tag names the grade. Check it matches your drawing, usually Fe 500.
- Look for the ISI mark.
The bar should carry the ISI mark and the maker’s name.
- Match the test certificate.
Every dispatch should carry a test certificate. Match its heat number to the bundle tag.
- Do the bend test.
Bend a piece and check the outer surface of the bend for cracks.
- Check the ribs and straightness.
Ribs should be even in pitch and height. Bars should be straight and free of kinks.
- Check the size.
Confirm each diameter matches your bar schedule.
If a bar fails any of these, it does not belong in a house you want to stand for decades.
Frequently asked questions
What grade of TMT bar is best for a house?
Fe 500 is the standard grade for most residential buildings. If the house is in a higher seismic zone or the engineer specifies a ductile grade, use Fe 550D.
What is the difference between TMT and cold-twisted bars?
TMT bars are heat treated, with a hard outer layer and a tough, ductile core. Cold-twisted bars get their strength by twisting, which uses up much of their ductility. TMT is the right steel for a house that has to last.
What sizes of TMT bar do I need for a house?
Typically 8 mm for ties and stirrups, 10 to 12 mm for slabs, 16 mm for beams and lighter columns, and 20 mm and above for heavier columns and footings. The exact sizes come from your structural drawing.
How much TMT steel does a house need?
A common rough guide is 3.5 to 4.5 kg per square foot of built-up area, so a 1,000 sq ft house uses roughly 3.5 to 4.5 tonnes. Order from your engineer’s bar bending schedule, not the rough guide.
How do I know the TMT bars are genuine?
Check the ISI mark on the bar and the grade on the bundle tag, and match the heat number to the test certificate. Both come with every RD TMT dispatch.
Is RD TMT's steel BIS certified?
Yes. RD TMT bars are made to IS 1786:2008 and carry the ISI mark under BIS licence CM/L-6200193709, with a NABL lab test certificate on every dispatch.
What is the price of TMT bars for a house in Bengaluru?
Price depends on size, quantity and the current market rate. Send your requirement and we will quote within one business day.
Is RD TMT approved for Bengaluru housing projects?
The Bangalore Development Authority has approved RD TMT Fe 550 and Fe 550D bars for its housing projects. For other listed-brand requirements, ask our team.
How do I get a quote?
Send the grade, sizes, quantity and delivery location, or your bar bending schedule, and our team will prepare a quote.