Python 2, 123 112 110 109 100 98 bytes
i=n=input()
while i:a=i%2;print' '*(n-i)+'\%s/'%['_',((-~i/2)*'/ \ |'[a::2])[a:-1-a]][i>1];i-=1
Saved a bunch of bytes by using input and string formatting as in Rod's answer