Hello! We are in the process of installing new plumbing for the kitchen, and for this, we need to make holes in two of the floor joists (there's a basement underneath). The plumber suggested making the holes as low as possible in the joist, about 5mm from the bottom. This is to ensure the correct slope and because it’s best for the joist.
The joists are about 3 meters long and run from the middle of the house to the outer wall. One of the joists rests on a basement wall. The holes to be made are 80mm, and the joists are approximately 170mm high. Will we encounter problems from this? How can we reinforce the joists in the best way?