-
I’m worried about the load baring nature of the joists, surely I can’t just cut one out?
In the short term - depends what it's supporting. It might need propping either side if it's a critical one. But this is how loft hatches are fitted so yeah you can cut one (no more, but if your joists are like mine that should be plenty big enough).
You should really get a structural engineer in to advise, but the answer's likely to be noggins either side of the hatch and sistering the joists either side of the one you cut. If your joists are like mine they'll be old size (mine are 63 x 175) which is overspecced so you can use 47mm C24 carcassing instead. I had a structural engineer round on Friday and he said that was AOK (and joist hangers for your noggins > skew nailing).
-
Why do you need to cut a joist? Are you not cutting through floorboards, which are perpendicular to the joists? You just need to find the joist, then cut the floorboards above at the central part of the joist and lift the boards, that gives you access.
You can make it a hatch by joining the cut floorboards together. We have a few in our place and its just a hatch in the floorboards, no joist has been cut. Or am I misunderstanding your setup?
Do you have an under stairs cupboard. My parents house had a hatch in there. You can square out the joists once you've lifted a few boards, it's the same setup as a loft hatch really.