Do I need a permit for a full bathroom remodel in
Fairfax, Virginia?

You're replacing an old vanity sink with a new one (same location, 24-inch wide), new faucet (code-compliant), and new toilet in the existing location. No wall moves, no new drains, no new vent lines, no electrical circuit additions (existing GFCI outlet is adequate). This is cosmetic surface work and is exempt from permitting under Fairfax code. However, if the existing vanity drain is 1.25-inch and your new vanity has a 1.5-inch drain (different P-trap size), you'd need to adapt or re-route the P-trap under the sink; as long as you're not moving the drain location in the floor or wall, this is still exempt. The toilet swap is similarly exempt if you're not moving the closet flange location. You do not need a permit. However, you should verify existing GFCI protection is within 6 feet of the sink (measure from sink basin edge)—if it's not, upgrading to a GFCI outlet (or replacing the vanity outlet with a GFCI combo outlet) is not a permit trigger but is required by NEC 210.8. Cost: Vanity $400–$1,500, faucet $150–$500, toilet $200–$400, labor $800–$2,000. Total: roughly $2,000–$5,000 out of pocket, zero permit fees, done in 3–5 days with a licensed plumber or handyman. Inspection: None required.

You're relocating the toilet from the north wall to the south wall (roughly 8 feet away), relocating the sink vanity from east to west (4 feet), and adding a new exhaust fan that doesn't currently exist (home has no duct, just an old wall louver). New drains and vent lines will run through the existing floor joist cavity or may require notching studs. This triggers permitting because: (1) relocated toilet requires a new branch line, P-trap, and vent connection, (2) relocated sink requires a new drain and hot-water line, (3) new exhaust fan requires a 4-inch duct to the exterior. The home was built in 1970, so lead-paint rules apply (EPA RRP notice required, contractor must be RRP-certified or you must assume the RRP burden). Your plan submission must include: floor plan with old and new fixture locations, drain routing showing P-trap locations and slope (1/4 inch per foot), vent stack tie-ins (size and connection point), electrical plan showing new 20-amp circuit for exhaust fan and GFCI/AFCI outlets, exhaust duct routing (4-inch diameter, exterior termination with rain cap, no damper). Fairfax plan review will flag if trap-arm length exceeds code (roughly 2.5x pipe diameter in horizontal run before the vent stack), so pre-measure: if your toilet is 8 feet from the main stack and you're using 3-inch drain line, the maximum trap arm is about 7.5 feet (3 x 2.5), so you're close—a 3-inch line might require an 1.5-inch secondary vent drop to the toilet location. Bring a plumber into plan-phase conversations. Exhaust duct routing: if the bathroom is interior and the attic is 20 feet away, plan for 20+ linear feet of rigid 4-inch duct (not flex duct, which can sag and trap moisture), with a rain-cap terminator through the soffit or roof. Fairfax inspectors will ask to see the terminator location during rough mechanical inspection. Cost: Plumbing work $3,000–$7,000 (new drain lines, vent, traps, fittings), electrical $500–$1,500 (new circuit, GFCI outlets, fan wiring), exhaust fan and duct $400–$1,200 (fan unit, 20+ feet of duct, rain cap, misc.), labor $2,000–$4,000. Permit fees: $350–$600 plus $150 per inspection (rough plumbing, rough electrical, final = 3 inspections = $450). Total project: $6,500–$15,000. Timeline: 4 weeks plan review, 2–3 weeks construction, 2 inspections minimum (rough and final). Lead-paint containment: contractor must follow EPA RRP protocols (plastic sheeting, HEPA vacuum, etc.), cost roughly $500–$1,500 built into labor estimate.

You're gutting the tub, capping the old tub drain (or using it for the shower drain), and building a new shower enclosure with a curb-less threshold and floor pan. The floor framing will be modified to slope toward a central drain or linear drain channel (minimum 1/8 inch per foot slope), and the wall framing will change to accommodate a corner shower seat or niche. This triggers permitting because: (1) tub-to-shower conversion changes the waterproofing assembly (IRC R702.4.2), (2) floor framing modification for slope and drain support, (3) wall framing changes. You qualify for an owner-builder permit if you own the home, occupy it as your primary residence, and are not hiring a general contractor (you can hire subs for specific trades). Fairfax owner-builder permits require you to pull the permit and schedule inspections yourself; you're liable for code compliance. Plan submission: floor plan showing new shower footprint, drain location, slope direction; wall section showing waterproofing system (e.g., cement board + fabric-reinforced membrane, or Schluter preformed curb system), substrate specification, grout sealant brand (name it specifically), framing changes if joists are sistered or notched. Fairfax plan reviewers will ask for a waterproofing system specification sheet; generic 'membrane' is not acceptable. Expected rejection points: (1) missing waterproofing detail, (2) unclear floor slope direction, (3) grout sealant not epoxy-grade (acrylic sealers fail in 2–3 years in humid climates like Fairfax piedmont), (4) old tub drain being reused without trap inspection (old trap may be damaged or have improper slope). Pro tip: have your plumber scope (camera inspect) the old tub drain before plan submission; if it's corroded or has a belly, you'll need a new P-trap and drain line (adds $500–$1,500). Waterproofing system choice: pre-fabricated Schluter Linear shower (factory-assembled curb + pan, certified assembly) is the fastest and most defensible option for a curb-less design and costs $2,000–$4,000 all-in; site-built cement board + membrane (Schluter KERDI, Hydroban, or equivalent) costs $1,000–$2,000 but requires careful installation and is a common re-inspection point. Fairfax inspectors will visually inspect the waterproofing membrane before tile application (do not tile until rough waterproofing inspection is signed off). Electrical: if you're adding a heated floor mat in the shower pan, that's a dedicated 20-amp GFCI circuit ($300–$800). Cost: Plumbing (drain scope, new trap if needed, P-trap fittings) $800–$2,000, waterproofing system $1,500–$4,000, framing/flooring modifications $1,000–$2,500, tile and grout $2,000–$4,000, heated floor (optional) $400–$1,000, labor (DIY or owner-builder responsible for permits and scheduling; tile work is typically hired out) $2,000–$5,000. Permit fees: $300–$600 plus $150 per inspection (rough plumbing, rough framing, waterproofing before tile, final = 4 inspections = $600). Total project: $8,000–$19,000. Timeline: 3–4 weeks plan review (waterproofing detail often requires revision), 4–6 weeks construction with inspection pauses (roughly 1 week per inspection cycle). Owner-builder advantage: you save contractor markup (typically 20–30% of labor), but you're on the hook for code compliance. Fairfax Building Department staff are helpful with owner-builder questions; call ahead (phone below) to clarify plan requirements before submission.