Hello, I'm a timber structure engineer, I've gone through your job description and realized that you are making some renovations to your home, I see that you want to modify the existing rafters or you might need to replace it with new ones with the same depth and add new floor joists, I can provide you floor framing plans for the attic space, in addition to calculation sheets for timber columns, beams and joists as per IBC code, I can also check the safety of the entire floors, please send me the CAD file as I can help you to get permit, I have done similar projects like yours, please check my portfolio, if you want a safe and economic structure just drop me a message to discuss details.