Jimy B

Hello all, I am an artist and architectural researcher. I plan on later renovating a building in Suffolk, but am currently converting a former barn in Germany into an exhibition space for contemporary art. If all goes well I will post quite some questions on this forum! Thanks for having me!! If I may, my first dilemma: I need to build a staircase with full (human) height access to the 1st floor of the said barn. Ideal would be to cut through the lower joist. I realise this is structurally challenging, but I am wondering if there is any kind of precedent for this kind of intervention? I am thinking of bracing both sides of the remaining rafter to the wall below, as this has significant mass and is around 27 inches thick (70 cm). The reason to cut through the lower joist, is that the distance between bottom and top joists is about 62 inches (160cm), - terrible for bumping heads. The loads on the bottom joist: You can see central poles resting in centre of lower joist, stress which is distributed downwards through smaller vertical poles and a wall on the far side. I am quite sure it serves as a tension tie to prevent lateral spreading/bowing of the exterior walls. Any advice, pictures, examples very much appreciated! Thanks in advance, James