I-joists are engineered truss joists that are lighter and less expensive than typical floor joists. There are two parts to an I-joist, the flange and the web. The flange cannot be modified. Cutting, notching, or putting holes in the flange will weaken an I-joist. The web can be drilled, but should not be over cut. The distance between holes in the web must be no less than 2x diameter of the hole, minimum.