Wood joist I-JOIST – a structural element used in the construction of the walls, ceiling and roof of the house. The wall of the beams is made of OSB-3 board, and the shelves are made of glued, planed wooden chips. The secondary beams I-BEAM are dimensionally accurate, light and strong. They do not bend over time like regular wooden beams. Also, secondary beams are much lighter than reinforced concrete or wooden beams, which is why they are especially popular with roofers, as