Gaithersburg is a very-high cost-of-living market — pricing guide and permit rules below.
Gaithersburg window replacement rates: $3,000-$10,000 per system. Always get 3 written quotes and verify MD licensing at Maryland MHIC (dllr.state.md.us). Sales tax on materials: 6%.
Gaithersburg requires permits when work exceeds $500 or involves full system replacement. Your licensed contractor pulls the permit — if they ask you to pull it, that's a red flag.