john cunningham
Hi Cameron It's probably 5" because it's a 4" brick wall with plaster either side. Things to check. 1/. Is there a wall above it. 2/. Do the floor joists run into it, check the floorboards do they run paralel to the wall, if so the floor joists run into it and wll need support 3/. The thickness of the wall does not mean it is not load bearing. 4/. It's best to contact building control. They will have to check the size of the r.s.j. Before it is boxed in. 5/. Structural engineer will be required to decide the size of the r.s.j. I understand you can find a structural engineer on line. You send them the details and they will send you the calculations, for a fee Best of luck Jkcunningham
