A tub-to-shower conversion takes out the tub, moves the drain and valve, sets a molded base or a sloped tile floor over waterproofing, then adds walls and glass. National guides put it at $1,500–$8,000 (HomeAdvisor) or $2,000–$12,000 (This Old House). In Duluth, it needs a building permit and a plumbing permit.
The eight steps of a conversion
A conversion looks like a fixture swap, but it's really a small remodel inside a five-foot alcove. Each step covers the one before it, so the order below doesn't change, and the plumbing steps get inspected before the walls close.
| Step | What happens | Good to know |
|---|---|---|
| 1. Tub out | Water off, spout and handle removed, the tub pulled or broken up in place and hauled away | A cast-iron tub can weigh several hundred pounds, so it usually leaves in pieces |
| 2. Floor and framing check | Subfloor and joists under the tub inspected for rot from years of small leaks | Soft wood gets replaced now, before anything covers it |
| 3. Drain moved or resized | Drain line and trap reworked to land where the new base or tiled floor needs it | Plumbing permit work; the floor may need opening between joists |
| 4. Valve and supply | Valve moved up the wall or replaced, supply lines reworked, showerhead arm set | Plumbing permit work; inspected while the wall is open |
| 5. Base or sloped floor | Molded base leveled and set, or a mortar bed sloped to the drain | The biggest single choice for price and look |
| 6. Waterproofing | Backer board or foam board, then a membrane tied into the drain; flood-tested where the system calls for it | Grout alone never keeps water out of the wall |
| 7. Walls | Tile, or panel walls glued and sealed to the base | Tile needs grout cure time; panels go up faster |
| 8. Glass and trim | Opening measured after the walls are done, glass fitted, trim, caulk and final inspection | Custom glass is ordered from final measurements, which adds a wait |
The drain is the step homeowners tend to underestimate. Minnesota's plumbing code sizes a bathtub trap at 1-1/2 inches and a single-head shower trap at 2 inches (Minn. R. 4714.0702), so the old tub trap usually gets replaced, not just reconnected. Molded bases come with the drain at the left, right or center, and picking one that lines up with the joists under the floor can keep the drain move short.
The valve matters too. Most tub valves sit low, where you reach them from outside the tub, and a shower valve belongs higher on the wall. If yours is an old two-handle valve, replacing it with a new pressure-balancing valve is the time to do it, since the wall is already open.
Molded base or tiled floor
A molded base, acrylic or solid-surface, is one piece with the slope and drain built in. It goes in quickly, has no grout lines on the floor, and pairs with panel walls or tile. Its limits are size and shape: it comes in set widths and depths, and a standard 60-inch base drops right into most tub alcoves, but an odd-sized or out-of-square alcove in an older Duluth house may need shimming, filler strips or a custom-order base.
A tiled floor is built on site: a mortar bed sloped to the drain, or a foam tray system, then a waterproof membrane and tile. It fits any footprint, allows a lower curb or a linear drain, and matches tile you already love. It also costs more and takes longer, because every layer has to cure. Small floor tiles, or ones with a textured finish, give better footing when wet than a large polished tile.
Either way, the waterproofing is what keeps the wall dry. With a liquid membrane such as RedGard, each coat typically dries in 1 to 1.5 hours but can take as long as 12, and the shower can be flood-tested only after both coats have fully cured (Custom Building Products). On an outside wall, a sound membrane also helps keep shower moisture out of a cold wall cavity through the winter.
How long a conversion takes
Plan on the bathroom being out of service for the whole job, not just the working days. A molded base with panel walls is the quicker build, and a fully tiled shower takes longer because every layer has to cure, but what sets the pace isn't the hours of labor so much as the waits between them:
- Inspections. The plumbing rough-in gets inspected before the wall and floor close, so the schedule includes the inspector's visit.
- Curing. Mortar beds, membranes, thinset and grout each need their cure time, and a cold, unheated bathroom in January slows every one of them.
- Glass. Frameless and custom glass is measured after the tile is done, then made to order, so a curtain rod may stand in for a stretch.
- Surprises. Rot under an old tub or a corroded drain adds repair time before the new base goes in.
When your flat written quote comes, ask us to mark the days you'll be without the shower, so you can line up another one to use.
Permits in Duluth and Superior
Duluth is clear on this one: "If a shower is replacing the current tub, then a building permit is needed" (City of Duluth). The same page lists what a bathroom remodel usually needs on top of that: a plumbing permit, an electrical permit, and an HVAC permit for the exhaust fan. A conversion takes the plumbing permit, since the drain and valve change, and a new light or fan adds the other two.
In Superior, the Permits Not Required list covers wall tile and cement board, but not moving a drain or valve, so plan on a plumbing permit for the altered piping and ask building inspection at (715) 395-7288 about the rest. Our Duluth and Superior permit guide covers other bathroom work.
How long does a tub-to-shower conversion take?
Longer than the working days alone, so plan for the shower to be out of use from tear-out until the final caulk has cured. A molded base with panel walls is the quicker build; a fully tiled shower takes longer, because the mortar bed, membrane, thinset and grout each need cure time. The plumbing inspection and made-to-order glass add waits of their own, and rot found under the old tub adds repair time. Ask for the days you'll be without a shower to be marked on your written quote.
Can a new shower base use the old tub drain location?
Sometimes, but the drain usually still gets reworked. Molded bases come with left, right or center drains, so one may line up close to the old opening, but Minnesota's plumbing code calls for a 2-inch trap on a shower, larger than a typical tub trap. The fitting under the floor usually changes even when the hole barely moves, and that work is done under a plumbing permit.
Is a molded shower base or a tiled floor better?
A molded base is quicker, cheaper and has no floor grout to clean; a tiled floor fits any shape and allows a lower curb or a linear drain. In a standard 60-inch tub alcove, a molded base is usually the practical pick. In an odd-sized alcove, or when you want a near-level entry, tile built over a sloped bed and a membrane is often the better answer.
Converting your tub? See shower remodeling for options, or bathroom remodeling if the vanity, floor and fan are due too. Call or text (715) 919-7956 with photos of the tub and the wall with the valve, or send your project. You'll get a flat written quote before work starts, and our on-site service fee is waived when you approve the work (pricing).