Garden state size up on Instagram: "TJI (trus joist I-joist) burn tests What to know…. Testing demonstrated that engineered wood I-joists generally fail faster than traditional 2x12 lumber in fire conditions, often collapsing under 4 mins due to rapid adhesive degradation. These tests show I-joists can burn faster, with potential for catastrophic, unexpected collapse, although they can be protected with gypsum board to meet 40-minute or 1-hour ratings. Key Findings from TJI Burn Tests: Rapid Fai