....ummmm, can't you take this up with the school?  Should there not be enough time left to catch up or at least discuss a redo on an failed assignment?  Also, how do you get into grad school and not be able to carrying a minimum B average?

Getting a failing grade in one course in your first semester, even if it's a studio, won't typically cause you to "fail the program".  The more likely results are one or more of:  a warning letter; academic probation; having to take that course over again in a later semester; or some sort of make-up plan.  If it's a core studio and you did horribly, and it's not something that can be taken in the spring or out of sequence, then it's possible you could be asked to withdraw for the spring semester and return in the fall to take it again then.  In any case you'd likely get a chance to talk with your academic advisors about it and try to negotiate some solution.

It's pretty rare to completely fail out of grad school - it usually wouldn't happen unless you have multiple failing grades, or continued unsuccessful semesters.  If the semester is not over yet you should try to talk to the professor of the course NOW and see what, if anything they recommend to give you a better chance of eeking out a passing grade.

It's not usually possible to jump directly into a 5th year of an undergrad B.Arch program anywhere.  Depending on the school and your past studies you would often be put back in sophomore or junior level studios, so it could take 2-4 years to finish that way.  It wouldn't be the route I'd recommend.  I think you should talk to your current program's people and try to get help charting a way forward.

Also, out of curiosity, what M.Arch program are you attending where anything less than a B makes you fail the whole program?  Almost all the M.Arch programs I know consider a C a "low pass", and you'd only hit even probation level if your cumulative GPA was less than B - not just one course.

Its unclear right now since there is still a final exam but advisors, professors, program director are all aware. It is actually a structures course..so unrelated to design studios...its been a while but I took two years of structures in undergrad which were always fine..If it were a matter of that was the only thing left i had to do and could just study for a while then there would be hope.. but the exam is literally right before studio final so it really puts a limit on how much studying is possible..i might share the later but i think its best not to right now. The rule is anything under a B is not considered passing. 

I failed a required course in grad school. The world didn't end. I just had to take it again the following fall. I had to also wait on the 2 more advanced courses for which it was a prerequisite,  so it changed around my schedule a bit from most of my classmates' but I did graduate on time.  I did get a letter about being on probation for a semester, but it didn't affect financial aid or anything and I even still won competitive awards.  If you fail you won't be the first who ever did, and I'm sure you won't be expelled over it!