Do I Need a Permit to Convert a Bathtub to a Walk-In Shower?
Converting a bathtub to a walk-in (curbless or low-threshold) shower is one of the most popular aging-in-place and bathroom modernization projects. In most jurisdictions, it requires a plumbing permit because the conversion involves relocating or resizing the drain from a bathtub drain (typically 1.5-inch with an overflow) to a shower drain (2-inch minimum per code, often with a linear drain body), modifying the water supply rough-in for a new valve position, and changing the waterproofing membrane (the shower pan liner or sheet membrane system must meet code requirements that differ from a bathtub surround). An electrical permit is also required if the project adds or relocates a GFCI-protected outlet, exhaust fan, or recessed lighting in the wet area. The conversion frequently involves structural work — cutting into the subfloor to reposition the drain, adding blocking for grab bars, or modifying the curb — which triggers a building permit in addition to the plumbing permit.
Do you need a permit?
Usually yes
What triggers a permit
- Relocating or resizing the drain from a 1.5-inch bathtub drain to a 2-inch shower drain
- Modifying the water supply rough-in (moving valve body, adding a thermostatic mixing valve or diverter)
- Cutting into the subfloor or floor joists to reroute the drain line to a new position
- Installing a new shower waterproofing system (pan liner, sheet membrane, or liquid-applied membrane)
Country-by-country detail
United States
Usually yes
- Permitting authority
- Local Building / Plumbing Permits Office
- Typical fee
- $100–$500
In the US, converting a tub to a walk-in shower requires a plumbing permit because the drain size must change from 1.5 inches (standard tub drain per IRC P3005.4.2) to 2 inches (minimum shower drain per IRC P3005.4.2), and the trap must be accessible. The shower receptor or finished floor must slope uniformly to the drain at ¼ inch per foot (IRC P2709.1), and the waterproofing membrane must extend at least 3 inches above the finished threshold height on all sides. For a curbless (zero-threshold) shower, the entire bathroom floor may need to be re-graded, which typically requires removing the existing subfloor — this triggers a building permit for structural work in addition to the plumbing permit. GFCI protection is required for any receptacle within 6 feet of the shower (NEC 210.8), and the exhaust fan must provide at least 50 CFM (IRC M1507.4). If the bathroom has only one bathtub and no other tub in the house, some jurisdictions flag the removal during plan review — while no IRC provision requires a bathtub, appraisers may note its absence as a functional deficiency in homes with multiple bedrooms.
Netherlands
Sometimes
- Permitting authority
- Gemeente (Omgevingsloket)
- Typical fee
- €0–€300
In the Netherlands, converting a bad (bathtub) to an inloopdouche (walk-in shower) within an existing badkamer is generally classified as internal renovatiewerkzaamheden (renovation work) that does not require an omgevingsvergunning, provided the work does not alter the draagconstructie (load-bearing structure), the brandcompartimentering, or the afvoer-aansluiting op het riool (sewer connection point). However, the new afvoer must comply with NEN 3215 for drainage capacity, and the waterproofing must meet the manufacturer's garantie-eisen (warranty requirements) — most gemeenten recommend using an erkend installateur for the leidingwerk. If the conversion requires cutting into the betonnen vloer (concrete floor slab) to relocate the afvoer, a constructief advies (structural assessment) may be required by the gemeente, particularly in gestapelde bouw (apartments/flats) where cutting into the vloer affects the draagvermogen for the verdieping below.
Poland
Sometimes
- Permitting authority
- Powiatowy Inspektorat Nadzoru Budowlanego (PINB)
- Typical fee
- 0–300 zł
In Poland, converting a wanna (bathtub) to a kabina prysznicowa (walk-in shower) within an existing łazienka is typically classified as a remont (renovation) under Prawo budowlane, which does not require a pozwolenie na budowę or zgłoszenie as long as the work does not alter the strop (floor structure), ściany nośne (load-bearing walls), or the location of the pion kanalizacyjny (main drain stack). A simple swap where the new shower drain connects to the same pion at the same point usually qualifies as a remont. However, if the conversion requires cutting into the strop to reposition the drain, adding a pompa zatapialna (waste pump) for a below-grade installation, or moving the pion, it becomes a przebudowa (reconstruction) requiring at minimum a zgłoszenie. In budynki wielorodzinne (apartment buildings), the wspólnota mieszkaniowa (housing community) may require notification or approval for work affecting wspólne instalacje (common systems). The instalacja wod-kan must comply with PN-EN 12056 for drainage sizing.