Light Steel Roof Truss Guide: Check SNI 8399:2017, AZ100 Coating and BMT vs TCT
Quality varies on the market, so check two SNI standards, the AZ100 coating and BMT versus TCT before buying a light steel roof truss.
Light steel (baja ringan) has become the main choice for house roof frames in Indonesia. But product quality on the market varies, so buyers should know how to read labels and specifications before purchasing.
The 2026 regulatory context
The Ministry of Industry is tightening SNI enforcement on steel products. According to ANTARA (23 February 2026), SNI for zinc-coated steel (BjLS) has been mandatory since 2008 and for aluminium-zinc coated steel (BjLAS) since 2009, with Ministerial Regulation 67/2024 as the basis for the latest strengthening. The Indonesian Iron and Steel Industry Association (IISIA) welcomed mandatory SNI for a number of steel products from 20 May 2026 and called for harmonised standards from raw material through downstream products such as roofing, walls, light steel and floor deck.
Two SNI standards to check
As explained by distributor PT Kencana Baja Trada, two standards matter for light-steel roof trusses: SNI 4096:2007 for the raw material, aluminium-zinc alloy coated steel sheet and coil, and SNI 8399:2017 for light-steel roof truss profiles. The profile standard requires an aluminium-zinc coating of at least AZ100 and a minimum thickness of 0.65 mm for roof truss products.
Understanding BMT and TCT
BMT (Base Metal Thickness) is the thickness of the steel before coating. This figure indicates the material's strength and is used in structural calculations.
TCT (Total Coated Thickness) is the thickness after aluminium-zinc, resin or paint coating. TCT does not indicate core strength, but it matters for corrosion resistance.
Coating thickness is TCT minus BMT. For example, an AZ100-coated C-channel with BMT 0.70 mm and TCT 0.75 mm has a 0.05 mm (50 micron) coating. Both can be measured with a micrometer.
Buying checklist
Check the print on each member: brand, SNI mark, BMT/TCT values and coating class (e.g. AZ100). Measure a sample with a micrometer if possible. Make sure the installer's structural calculation uses BMT, not TCT. Ask for proof of SNI certification and a written warranty. Do not be tempted by much lower prices without clear specifications, because a roof frame is about occupants' safety.
Buying materials with homeX
homeX, a one-stop building materials and furniture service platform in Indonesia, offers a showroom where you can see products in person, warehousing with tracked stock and delivery from Tangerang. Our team can help you choose materials that suit your project.
FAQ
Which SNI standards apply to light steel roof trusses? SNI 4096:2007 for the aluminium-zinc coated steel raw material, and SNI 8399:2017 for truss profiles, which requires at least AZ100 coating and 0.65 mm minimum thickness.
What is the difference between BMT and TCT? BMT is steel thickness before coating and indicates strength for structural design; TCT is thickness after coating and relates to corrosion resistance.
Light steel roof truss: related articles and products
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Source: PT Kencana Baja Trada – Pentingnya SNI pada Baja Ringan; PT Kencana Baja Trada – Perbedaan BMT dan TCT; ANTARA News, 23 Feb 2026; IISIA, 13 Mei 2026