  Complex integrated circuits require multiple wiring layers. In complementary
metal-oxide-semiconductor (CMOS) processing, these layers are robustly
separated by amorphous dielectrics. These dielectrics would dominate energy
loss in superconducting integrated circuits. Here we demonstrate a procedure
that capitalizes on the structural benefits of inter-layer dielectrics during
fabrication and mitigates the added loss. We separate and support multiple
wiring layers throughout fabrication using SiO$_2$ scaffolding, then remove it
post-fabrication. This technique is compatible with foundry level processing
and the can be generalized to make many different forms of low-loss multi-layer
wiring. We use this technique to create freestanding aluminum vacuum gap
crossovers (airbridges). We characterize the added capacitive loss of these
airbridges by connecting ground planes over microwave frequency $\lambda/4$
coplanar waveguide resonators and measuring resonator loss. We measure a low
power resonator loss of $\sim 3.9 \times 10^{-8}$ per bridge, which is 100
times lower than dielectric supported bridges. We further characterize these
airbridges as crossovers, control line jumpers, and as part of a coupling
network in gmon and fuxmon qubits. We measure qubit characteristic lifetimes
($T_1$'s) in excess of 30 $\mu$s in gmon devices.
