BMT vs TCT in Light Steel: What the Thickness Means, AZ100 and SNI 8399 Checks
The terms BMT vs TCT light steel often lead buyers to compare prices wrongly. BMT (Base Metal Thickness) is the core steel thickness before coating, while TCT (Total Coated Thickness) includes the anti-rust coating and paint. A C-channel labelled "0.75" may mean 0.75 mm TCT with only 0.70 mm of core steel.
Key Facts
- BMT is the base steel thickness before resin, aluminium-zinc or paint coating, and indicates strength in structural design (2024-06-03, source: PT Kencana Baja Trada (KS light steel), 3 Jun 2024).
- TCT is the thickness after coating; it does not reflect core strength but helps prevent rust (2024-06-03, source: PT Kencana Baja Trada (KS light steel), 3 Jun 2024).
- KS C-channel with AZ100 coating: BMT 0.70 mm and TCT 0.75 mm, so the coating is 0.05 mm or 50 microns (2024-06-03, source: PT Kencana Baja Trada (KS light steel), 3 Jun 2024).
- KS products follow SNI 8399:2017 (light steel framing profiles), SNI 4096:2007 base material and G550 grade for C-channels (2024-06-03, source: PT Kencana Baja Trada (KS light steel), 3 Jun 2024).
BMT vs TCT light steel: which one to design with
Roof truss design uses BMT because strength comes from the core steel. TCT only indicates rust protection. When comparing quotes, ask for the BMT, the coating class (AZ100 = 100 g/m² aluminium-zinc) and the steel grade (G550).
How to check on site
- Measure with an analogue or digital micrometer in millimetres; a field reading is TCT.
- Subtract the stated BMT from TCT to get coating thickness.
- Check the print on the profile: brand, SNI, size and thickness.
Common mistakes
- Comparing two "0.75" prices without knowing one is BMT and the other TCT.
- Using thin profiles for wide spans without an applicator's calculation.
BMT vs TCT light steel: related articles and products
- Light steel prices per bar 2026
- Light steel factories in Indonesia
- Light steel roof truss cost per m² 2026
- homeX building materials catalog
FAQ
What is the difference between BMT and TCT? BMT is the core steel thickness before coating and sets strength; TCT is total thickness after anti-rust coating and paint.
How is coating thickness calculated? TCT minus BMT; the KS example is 0.75 − 0.70 = 0.05 mm or 50 microns.
Which SNI covers light steel profiles? SNI 8399:2017 for light steel framing profiles; the sheet material follows SNI 4096:2007.
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