Bathroom Remodel Permit in Derby, KS (2026)

Research by DoINeedAPermit Research Team · Updated May 2026

The Short Answer

A full bathroom remodel in Derby requires a permit if you relocate plumbing fixtures, add electrical circuits, install a new exhaust fan, convert a tub to shower, or move walls. Surface-only work (tile, vanity swap in place, faucet replacement) is exempt.

Derby follows Kansas State Building Code (currently the 2015 IBC/IRC) with minimal local amendments, which means your permit pathway is straightforward but code interpretation occasionally hinges on how the Derby Building Department reads duct termination and waterproofing details. Unlike some Kansas cities that have adopted the 2021 code, Derby's current code edition can be slower on items like low-slope shower pan requirements — verify duct routing and membrane specs directly with the inspector before rough framing. The City of Derby Building Department reviews plans in-house (no outsourced review), so turnaround is typically 1–2 weeks for a complete set; expect questions on GFCI layout and trap-arm length if you're relocating drains. Derby's frost depth of 36 inches matters mainly for exterior vents and any foundation-level work, but interior bathroom work rarely triggers that. Fee structure runs roughly 1.5–2% of declared project valuation: a $15,000 bathroom remodel pulls a $250–$350 permit. Owner-builders are allowed for owner-occupied homes, so you can file without a contractor license if the home is your primary residence.

What happens if you skip the permit (and you needed one)

Stop-work order issued by City of Derby inspector: $250–$500 fine, plus you'll be required to pull the permit retroactively and pay double the original fee (total $500–$700 depending on valuation).
Insurance claim denial if a plumbing or electrical failure traces back to unpermitted work; water damage from an unpermitted shower pan failure can void coverage entirely, costing $5,000–$25,000 out-of-pocket.
Lender or appraiser discovery during refinance or home sale triggers mandatory remediation: you'll need to hire a licensed contractor to complete unpermitted work legally, adding 20–30% to the original project cost.
Neighbor complaint on visible scope creep (dumpster, extended construction) can escalate to city enforcement, forcing removal of non-permitted work and additional fines of $100–$300 per day of non-compliance.

Derby, Kansas full bathroom remodel permits — the key details

The threshold for a permit in Derby is clear: any work that involves moving a fixture (toilet, sink, tub/shower, vanity), running new electrical circuits (including a new exhaust fan circuit), installing a new or replacement exhaust fan with duct, converting a tub to a shower (which changes the waterproofing assembly under IRC R702.4.2), or altering walls triggers the requirement. The City of Derby Building Department does not exempt 'minor' fixture moves or 'quick' electrical runs — if the work shows on a plan or involves code-regulated systems (plumbing, electrical, ventilation), a permit is due before you start. Surface-only cosmetic work — tiling over existing substrate, swapping a faucet aerator, replacing a vanity in the exact same location without new rough plumbing — is exempt. The distinction is strict: if existing pipes and drains stay in place and you're not opening walls or running new circuits, you're clear. Many homeowners confuse 'full remodel' with 'gut remodel'; a full bathroom remodel often means new finishes but may not include new fixture locations, which is why the calculator questions are essential to your permit decision.

Derby applies the 2015 IBC/IRC without significant local amendments, so you're looking at baseline code: IRC P2706 for proper drainage slopes and trap-arm length (max 42 inches for a 1.5-inch trap), IRC E3902 for GFCI protection on all receptacles within 6 feet of a sink, and IRC M1505 for exhaust fan CFM sizing (typically 50 CFM for a full bath, 100 CFM if there's a tub enclosure). The exhaust fan duct must terminate to the outdoors (not into the attic — a common rejection reason); IRC M1505.2 requires hard ducting with proper slope and insulation in Kansas climate zones 4A/5A to prevent condensation. For shower/tub work, IRC R702.4.2 mandates a waterproofing membrane (cement board + liquid membrane, or a pre-formed pan liner system) behind all tile; the Derby inspector will want to see the membrane brand/type on the plan or in a material specification sheet. If you're relocating a drain or moving the toilet, the trap-arm (the horizontal pipe from the trap to the vent stack) cannot exceed 42 inches, and the slope must be 1/4 inch per foot minimum. These details are where most plans get flagged: an undersized duct, a missing membrane callout, or a trap arm that's 48 inches long will require a revision before the rough-in inspection. Pressure-balanced valves (mixing valves) are not mandated for a basic tub/shower conversion, but the inspector may ask if the new valve is identified; if you're reusing an old valve and moving it, it should be tested for proper operation.

Derby's Building Department processes plans through a single in-house reviewer, which is typically faster than regional plan-review services but also means less tolerance for incomplete submittals. You'll submit two sets of plans (some jurisdictions ask for three); include a floor plan showing fixture locations, a plumbing riser diagram (especially if you're moving drains), an electrical layout with GFCI and circuit info, and a detail or note specifying the shower waterproofing system. The fee is calculated on declared valuation: a $15,000 full bathroom remodel (fixtures, tile, plumbing, electrical, labor estimate) yields roughly $250–$350; a $25,000 scope runs $350–$500. Derby does not charge for plan review separately; the permit fee covers staff time. Once submitted, expect 1–2 weeks for first review; if there are no major issues (missing details, code conflicts), you'll get approval or a request-for-information email. Do not start work while waiting for approval — the city has had enforcement actions against contractors who begin framing before final approval. Inspections follow the standard path: rough plumbing (drains, vent stacks, water supply stubouts in place), rough electrical (circuits, boxes, GFCI protection verified), and final (fixture installation, duct termination, waterproofing sealed). In a full remodel, the inspector usually requires all three rough inspections; if you're doing a cosmetic-only job (no wall moves), you may skip the framing inspection. Call ahead to schedule each — don't assume a walk-by is automatic.

A key local wrinkle: Derby's frost depth is 36 inches, and the city sits on a mix of loess and expansive clay, especially on the east side. This doesn't directly affect interior bathroom work, but if your vent duct has any exterior termination or if you're tying into a new drain that runs near the foundation, the inspector will check that the duct or pipe penetration is sealed properly to prevent frost heave over time. Loess is prone to settlement, so older homes (pre-1970) in Derby sometimes have slightly uneven floors; when you're relocating a toilet or tub, pay attention to slope — if the floor is not level, the trap-arm slope becomes trickier. Use a laser level and run the new drain lines slightly higher than the existing one if needed. The 36-inch frost depth also means that any exterior vent duct must be buried at least that deep or sloped to drain (per IRC M1505.3) to avoid freeze-up in Kansas winters — not a trivial detail in Derby's 5A climate zone. Lead-paint testing is not required by the city (that's federal EPA jurisdiction), but if your home was built before 1978 and you're disturbing existing paint during demolition, you should follow EPA RRP Rule practices: contain dust, use HEPA vacuums, and document your method. The city doesn't enforce it, but your contractor's liability insurance will; skipping lead containment on a pre-1978 home is a common coverage denial.

From a practical standpoint, the fastest path to approval is a complete, clear submittal: a scale floor plan with all fixture dimensions and rough locations, a one-line electrical diagram showing the new circuit(s) and existing panel load, a detail drawing or photo of the planned waterproofing system (especially if you're using a product the inspector hasn't seen), and a duct routing sketch if you're adding or relocating an exhaust fan. Include the product names (e.g., 'Schluter Kerdi waterproofing membrane') rather than generic descriptions — the inspector can then verify code compliance without a follow-up email. If you're hiring a contractor, they'll handle the permit filing; if you're owner-building, you'll file it yourself at City Hall or via the city's online portal (verify the current URL with the city directly, as portals are sometimes updated). The turnaround from submission to approval is typically 10–14 days; inspections can often be scheduled within 2–3 days of a request. Plan for 3–4 weeks total from permit to final sign-off, assuming no rejections. Many full bathrooms in Derby take 6–10 weeks of actual construction time, so the permit process is usually not the bottleneck — material delays or contractor scheduling are more often the constraint.

Three Derby bathroom remodel (full) scenarios

Scenario A

Moving toilet to opposite wall, new tile surround, exhaust fan duct reroute — 1960s rambler in central Derby

You're gutting a small bathroom in a 1960s rambler on the west side of Derby (sandy loess soil) and relocating the toilet from the south wall to the east wall, about 15 feet from the existing stack. You're also replacing the tile surround with a cement-board-and-liquid-membrane shower system, adding a new ADA-compliant vanity, and rerouting the exhaust fan duct to exit the roof (current duct is shared with a bedroom, which is a code violation). The scope is $14,000 (materials and labor). This absolutely requires a permit. You'll file a plumbing/electrical combo permit; the fee will be roughly $250 based on $14,000 valuation. The plumbing plan must show the new toilet location, the trap-arm length (you'll measure 12 feet from trap to stack, which is well under the 42-inch max for the horizontal run, so the inspector will approve it), and the vent routing (reusing the existing stack is fine as long as the new toilet ties in above the existing connections). The electrical plan must show the new exhaust fan circuit (a dedicated 20A circuit if it's a 100 CFM fan, which is standard for a tub/shower combo) and GFCI protection on the vanity outlet(s). The shower waterproofing detail is critical: you must specify 'cement board substrate with liquid-applied waterproof membrane per ASTM D6904' or name a specific product (Schluter Kerdi, Redgard, etc.); the inspector will verify the membrane is applied to the threshold pan and up 60 inches on the walls (IRC R702.4.2). The duct rerouting plan must show the duct terminating above the roofline with a proper cap and slope; if you're running new duct through the attic, it must be insulated to prevent condensation in the 36-inch frost zone (common failure in Derby's 5A climate). Inspections: rough plumbing (new drain stubout, vent routing), rough electrical (new circuit, GFCI wiring), and final (fixture set, duct termination, waterproofing sealed). Timeline: 2 weeks plan review, 3 days to schedule rough plumbing, 3 days rough electrical, 5 days framing/drywall, 2 days final inspection. Total project 6–8 weeks. Cost: $250 permit fee + $14,000 labor/materials = $14,250.

Scenario B

Tub-to-shower conversion with new waterproofing, existing plumbing stays, GFCI receptacle swap — 1980s bi-level in east Derby

Your 1980s bi-level on the east side of Derby (expansive clay soil zone) has a dated 5-foot tub enclosure that you want to convert to a walk-in shower. The existing drain, trap, and vent stack all stay in place — you're not moving the plumbing, just changing the finish. You are, however, replacing the wall finish with a full cement-board-and-membrane system (the current walls are likely original drywall, which cannot be exposed behind a shower per IRC R702.4.2). You're also upgrading the electrical: adding a second outlet with GFCI protection (current bathroom has one unprotected outlet). The scope is $8,500. This requires a permit. The trigger is the waterproofing assembly change: tub-to-shower conversions are exempt if you're installing a traditional acrylic or fiberglass shower base in the existing footprint with no wall reconstruction, but a full tile conversion requires a waterproofing plan. You'll file a plumbing/electrical combo permit; fee is $200 (lower valuation). The plumbing submittal is minimal — essentially a note saying 'existing trap, drain, and vent remain; new shower pan with cement board and membrane per ASTM D6904' — because nothing is being relocated. The electrical plan shows the new GFCI outlet location and confirms the circuit is a bathroom dedicated branch (not shared with other rooms per NEC 210.11(C)(1)). The waterproofing detail is the main focus: you must show the membrane extending from the pan up to at least 60 inches, covering all tile substrate behind the shower valve, faucet, and controls. Because the lot sits on expansive clay, the inspector may ask about grading and foundation issues (unrelated to the permit, but worth noting: expansive clay can cause differential settlement over decades, so check for cracks near the bathroom exterior wall — if your foundation is settling, the new waterproofing won't help much). The inspection sequence is plumbing (drain/trap check), electrical (GFCI installation), and final (membrane sealed, tiles grouted). You skip the framing inspection because no walls are being moved. Timeline: 1 week plan review, 2 days rough plumbing, 2 days rough electrical, 3 days tile work, 1 day final. Total 4–5 weeks. Cost: $200 permit + $8,500 labor/materials = $8,700.

Scenario C

Vanity swap in-place, faucet and sink replacement, existing tile patch — 2000s ranch in west Derby, owner-builder

Your 2000s ranch home on the west side of Derby (sandy loess soil, well-draining) has an older vanity and faucet in the master bathroom that you want to replace. You're removing the existing vanity and sink, patching some loose tile on the wall above (re-grouting only, no membrane work), and installing a new 30-inch vanity with a new faucet in the exact same location. The plumbing stubouts (hot/cold lines and drain) remain unchanged. You're not moving the toilet, tub, or any fixtures; there are no electrical circuit changes (the existing outlet stays where it is). The scope is $1,800. No permit is required. This is surface-only work: fixture replacement in the same location with no new rough plumbing, new electrical, or structural changes. You file no permit. However, verify that the new faucet you're buying will fit the existing hole spacing and drain size (usually 1.25-inch or 1.5-inch trap); if the new vanity's drain doesn't align with the existing drain, you'd need to move the drain, which triggers a permit. For this scenario, assume it's a straight swap — existing countertop has a pre-drilled faucet hole at 8 inches on center (standard); new vanity has the same spacing. You'll turn off the water at the main shutoff, unscrew the old faucet supply lines and drain tailpiece, remove the vanity, install the new one, and connect the new faucet. A plumber isn't required (though helpful if you're unsure about water-line connections); a licensed plumber would charge $200–$400 for the labor. For the tile patching, you can use a grout float and touch-up grout (no membrane involved, since you're just regrouting existing tile, not opening walls or replacing substrate). Cost: $1,800 materials (vanity, faucet, sink) + $200–$400 labor (if you hire help) = $2,000–$2,200. No permit fee. Derby Building Department will never know you did the work — and that's correct, because it's permit-exempt. However, if you're a detail-oriented owner and want to confirm the existing drain and supply lines are code-compliant (maybe the home was built in 1998 and you want to ensure the GFCI outlet is present), you could call the building department and ask for a brief verification, but it's not required.

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Waterproofing details that trip up Derby bathroom remodels

The single most common reason a bathroom remodel plan gets rejected in Derby is a vague or missing waterproofing specification. IRC R702.4.2 requires a waterproofing membrane behind all tile in wet areas (tub surround, shower, wet wall next to sink if tiled), but the code doesn't mandate one specific product or method. The Derby inspector will accept cement board + liquid-applied membrane (Redgard, Schluter Kerdi, etc.), a pre-formed synthetic pan liner (like a Schluter pan), or even a mud-bed pan with a PVC membrane if you document it. What fails is a submittal that just says 'tile surround per code' with no detail. You must show one of these systems on your plan or in a material specification sheet. The membrane must extend from the floor (under the threshold or in the pan) up at least 60 inches on the walls and cover all rough framing. If your shower has a built-in niche or bench, the membrane must wrap around it entirely (common miss: the niche is tiled but the back wall behind it is just drywall, which absorbs water and rots over time). The Derby inspector will ask to see a photo or sample of your chosen membrane product during the final inspection; don't wait until finish-out to decide — specify it now in the permit submittal.

GFCI and AFCI requirements for Derby bathrooms

All receptacles within 6 feet of the sink require GFCI protection per NEC 210.8(A)(1). In a full bathroom remodel in Derby, that typically means the vanity outlet and any other outlets on the sink wall. The GFCI can be installed as a receptacle (an outlet that has GFCI built-in) or as a breaker on the main panel (a GFCI breaker protects the entire circuit). For a new bathroom circuit, a GFCI breaker is cleaner; for an existing circuit being extended, a GFCI receptacle is simpler. The electrical plan must show which method you're using. Arc-fault circuit interrupters (AFCI) are required for all bedroom circuits in newer code (2020+), but Derby is on the 2015 IBC, so AFCI is not mandated for a bathroom remodel unless the bathroom is in a bedroom (rare). However, if you're running a new circuit for the exhaust fan, the NEC does not mandate AFCI for that circuit, only GFCI if the fan outlet is near water — which it typically isn't (the fan is mounted in the ceiling). The inspector will verify during rough electrical that the GFCI receptacle or breaker is correctly wired and tested (a GFCI test button must click when pressed). Many homeowners install a GFCI receptacle in the first position on a vanity circuit, which protects all downstream outlets — make sure the label is clear so a future homeowner knows the outlet is protected.

City of Derby Building Department
Derby City Hall, Derby, Kansas (verify current address with city website)
Phone: (316) 788-1500 or check city website for current number | Check derbykansas.org for online permit portal or call city hall for current URL
Monday–Friday, 8:00 AM–5:00 PM (verify locally)

Common questions

Can I do a bathroom remodel myself in Derby, or do I need a contractor?

Derby allows owner-builders to pull permits and perform work on owner-occupied primary residences. You do not need a contractor license to file the permit, but some work (plumbing, electrical) may require licensed subcontractors depending on the scope and your skill level. If you're moving plumbing or installing new electrical circuits, hiring licensed plumber and electrician subcontractors is strongly recommended — the inspector will verify their work. A full bathroom remodel is generally not a DIY task unless you have significant experience with plumbing, electrical, and tile waterproofing.

How long does the permit process take in Derby?

Plan review typically takes 1–2 weeks from submission. Once approved, inspections can usually be scheduled within 2–3 business days of a request. The actual construction time varies widely (4–10 weeks depending on scope and contractor availability). Total timeline from permit to final sign-off is usually 3–4 weeks of calendar time, but the actual work duration is much longer. Delays often come from material backorders or contractor scheduling, not the permit process itself.

What if my bathroom is in a pre-1978 home — do I need to test for lead?

Lead-paint testing is not required by the City of Derby; it falls under federal EPA jurisdiction (EPA RRP Rule). However, if your home was built before 1978 and you're disturbing existing paint during bathroom demolition, you should assume lead is present and follow EPA containment practices: HEPA vacuum, plastic sheeting, and wet-wipe cleanup. Your contractor's liability insurance may require this — skipping it could deny a claim if someone is exposed. Lead disclosure is required at sale but not by the building permit.

Do I need a separate permit for just replacing the toilet, faucet, or vanity?

No. Replacing a toilet, faucet, or vanity in the same location with no new plumbing rough-in is permit-exempt. You're only required to permit work if you move a fixture, add new circuits, install new vents, or change waterproofing (e.g., tub-to-shower conversion). A simple swap of fixtures in place is surface-only work and does not need city approval.

What happens if the inspector finds code violations during rough inspection?

The inspector will issue a correction notice or require a remediation plan (not a full rejection). Common items: a trap-arm that's too long, a GFCI that's not properly wired, or duct routing that doesn't terminate outdoors. You'll have a set time (usually 7–14 days) to correct the issue and request a re-inspection. Expect to pay for the re-inspection ($50–$100) if the violation is significant. Plan on 1–2 additional weeks if corrections are needed.

How much does a bathroom remodel permit cost in Derby?

Derby's permit fee is roughly 1.5–2% of declared project valuation. A $15,000 full remodel costs $250–$350 for the permit; a $25,000 remodel costs $350–$500. There is no separate plan-review fee; the permit fee covers staff time. The fee is due when you file the permit application. If you later discover the project scope is larger than originally declared (e.g., unexpected structural damage), you may need to amend the permit and pay an additional fee.

Can I start work before the permit is approved?

No. Derby Building Department requires a final approval before you begin any work, including demolition. Starting before approval can result in a stop-work order, a fine of $250–$500, and a requirement to pull the permit retroactively (paying double the original fee). If a neighbor reports visible construction activity, the city may enforce. Always wait for written approval (or a permit card issued by the city) before you begin.

What is the exhaust fan CFM requirement for a bathroom remodel in Derby?

IRC M1505 requires 50 CFM for a bathroom without a tub or shower, and 100 CFM for a bathroom with a tub or shower enclosure. Derby applies this standard. The duct must terminate outdoors (not into the attic) with a proper hood and slope to prevent condensation. If you're installing a 100 CFM fan, use a dedicated 20A circuit. The inspector will verify the duct routing and termination during the rough electrical and final inspections.

Do I need to pull a separate electrical permit for a bathroom remodel, or is it combined with plumbing?

In Derby, you can file a single 'combo' permit that covers plumbing, electrical, and mechanical work (e.g., exhaust fan). Some cities require separate permits for each trade; Derby typically allows one permit for a bathroom remodel. If the electrical work is extensive (adding multiple circuits, upgrading the panel), the city may request a separate electrical plan or recommend splitting the permits — call ahead to confirm. The fee structure is the same either way.

What is the frost depth requirement for bathroom remodels in Derby?

Derby's frost depth is 36 inches, which is relevant mainly for exterior vent duct and any foundation-level plumbing. Interior bathroom work is not affected. However, if your exhaust fan duct exits the roof or side wall, it must be insulated and sloped to drain to prevent freeze-up in the Kansas 5A winter climate. The inspector will check duct routing during the final inspection. If any new drain lines run near the foundation, they should be deep enough to avoid frost heave — though this is rare in a typical bathroom remodel.

Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current bathroom remodel (full) permit requirements with the City of Derby Building Department before starting your project.

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