GB/T 11263-2017 specifies strict dimensional tolerances:
1) Height (H): ±1.5mm for H≤200mm, ±2.0mm for 200mm<H≤400mm, ±3.0mm for H>400mm;
2) Width (B): ±1.0mm for B≤150mm, ±1.5mm for B>150mm;
3) Web thickness (d): ±0.15d (e.g., ±0.98mm for d=6.5mm);
4) Flange thickness (t): ±0.15t (e.g., ±1.35mm for t=9mm);
5) Length: ±50mm for fixed-length delivery (e.g., 12m beams can be 11.95–12.05m).
These tolerances ensure structural compatibility-e.g., consistent height allows beams to fit into prefabricated steel frames without modification.