--- url: https://qsteelcad.com/en/blog/light-steel-fire-design-turkey language: en alternate: https://qsteelcad.com/blog/hafif-celik-yangin-tasarimi updated: 2026-11-06 publisher: RENMAE Teknoloji ve Yazılım LTD. ŞTİ. --- # Fire design in light steel: what does Section 11 of the regulation require? For the first time, fire design for light steel buildings has its own section. Test or calculation? How much strength does steel lose at 500 °C? The tables and methods are in this article. ## Short answer Section 11 of the 2027 light steel regulation requires fire resistance to be shown by suitable fire tests or, where none is done, by calculation. In the calculation, steel yield strength and modulus of elasticity are reduced with the Table 11.1 factors; at 500 °C the yield strength factor is 0.45. ## Key points - Fire performance is shown by test or by calculation. - Test standards: EN 1365-1 (load-bearing wall), TS EN 1365-2 (floor and roof), TS EN 1364-1 (partition). - The yield strength factor is 0.68 at 400 °C, 0.45 at 500 °C and 0.28 at 600 °C. - There is a separate reduction table for joints: 0.55 at 500 °C, 0.22 at 600 °C. - Analysis with reduced properties is done under dead and live loads only. A thin-walled profile heats up quickly in a fire. That is why fire resistance in light steel comes mostly not from the steel itself but from the boards and insulation around it. Section 11 of the new regulation describes the fire resistance design of load-bearing wall and floor members and requires compliance with the principles of the Regulation on the Fire Protection of Buildings. ## How is fire resistance shown? The regulation requires one of two methods to be applied: | Method | How it is done | Output | | --- | --- | --- | | Fire test | Members are put through a standard test under loading; the temperature rise and the change in capacity are recorded | Test report and a document that the limit values are met | | Heat transfer analysis | Fire scenarios are set up, and the temperature distribution and load capacity are calculated numerically | Performance assessment | | Calculation with material factors | Member temperature is found from the ambient temperature curve, and material properties are reduced using the table | Load/capacity check | For testing, EN 1365-1 (load-bearing walls), TS EN 1365-2 (floors and roofs) and TS EN 1364-1 (non-load-bearing partition walls) are cited. Where no test is done, the calculation route is open. For the ambient gas temperature the text gives the following curve: Equation 11.1.1: ``` T ambient(gas) = 20 + 345 · log10(8t + 1) [°C] ``` ## How much strength does steel lose with temperature? | Temperature (°C) | Yield strength factor | Modulus of elasticity factor | | --- | --- | --- | | 100 | 1.00 | 1.00 | | 200 | 0.98 | 0.95 | | 300 | 0.88 | 0.83 | | 400 | 0.68 | 0.66 | | 500 | 0.45 | 0.48 | | 600 | 0.28 | 0.33 | | 700 | 0.16 | 0.21 | | 800 | 0.09 | 0.13 | | 900 | 0.05 | 0.08 | | 1000 | 0.03 | 0.04 | According to Table 11.1, linear interpolation can be used for values in between. What the table shows is simple: between 400 and 600 °C, steel loses most of its strength. The regulation also writes that properties at high temperature depend on the chemical composition, the level of cold forming and the production process. ## What does it say about joints? Section 11.4 sets a separate rule for connection points: the maximum thickness of protection material needed for the connected member to meet its fire resistance value is also maintained at the connection. This thickness is maintained throughout all joints. The variation of the strength factor with temperature for the tension and shear checks of connection elements is in Table 11.2: | Temperature (°C) | Strength retention factor | | --- | --- | | 20 | 1 | | 100 | 0.97 | | 150 | 0.95 | | 200 | 0.94 | | 300 | 0.90 | | 400 | 0.78 | | 500 | 0.55 | | 600 | 0.22 | | 700 | 0.10 | | 800 | 0.07 | | 900 | 0.03 | | 1000 | 0 | The difference between the numbers is notable: at 600 °C the joint factor of 0.22 falls below the profile's yield factor of 0.28. In fire design, the connection can be the limit before the member. The regulation also requires a check of whether the connection retains adequate strength after the fire. ## Which loads are used in the calculation? According to the text, the analysis is done with the reduced material properties under dead and live loads only, and an adequate load/capacity ratio is checked. In the member temperature calculation, convection and radiation are included; if there is sheathing, its thermal resistance is added to the calculation. ## What changes for the designer and the manufacturer? - Choose at the start which route will be used for your wall and floor types: test or calculation? - If you use a system with a test report, check that its scope matches your project. - Board type and number of layers are part of the fire resistance; they should not be changed on site. - Show in the detail that the protection thickness continues at connection points. - Restore the fire stop after service penetrations. - Tie the fire design to item 7.1 of Table 10.1 and to the calculation report. ## Does QSteelCAD do fire calculations? No. The program does not calculate fire resistance. Cladding and interior lining information is for presentation and takeoff; it does not replace a fire decision. Fire design is the responsibility of the project designer and engineer. ## Frequently asked ### Is light steel fire resistant? Resistance depends less on the profile itself than on the layers that protect it. The regulation requires performance to be shown by test or by calculation. ### At what temperature does steel lose strength? According to Table 11.1, the yield strength factor falls to 0.88 at 300 °C, 0.68 at 400 °C, 0.45 at 500 °C and 0.28 at 600 °C. ### Which fire test standards are cited? EN 1365-1, TS EN 1365-2 and TS EN 1364-1. Section 11 cites these standards for load-bearing walls, floors and roofs, and partition walls. ## Related solutions - [Create architecture from plan](https://qsteelcad.com/en/solutions/plan-to-architecture)