Converting a tub to a walk-in shower
Swap an old tub for a walk-in shower in Simi Valley. What happens to the drain, curb versus curbless entry, and why the conversion needs a City permit.
The most common bathroom request in Simi Valley is the simplest to describe: take out the tub nobody bathes in and put in a shower you can walk into. In most tract homes that means working inside the existing five-foot alcove, so the room keeps its size while the shower gets wider and easier to use.
It is still real plumbing work. The drain moves from the end of the tub to the center or edge of a shower pan, the valve usually moves up the wall, and the floor gets a new waterproof pan. That is why a conversion is permitted and inspected, not a weekend swap.
What happens to the drain when the tub comes out
A tub drains at one end, through an overflow and trap sized for a tub. A shower pan needs its drain where the floor slopes to it, and the trap and vent have to match. On a raised floor we reroute the line from the crawlspace. On a slab, the concrete around the old drain is cut out, the line is moved and the slab is patched before the pan is built.
This is also the moment to look at the original drain in older homes. If it is cast iron and already cracked, replacing the short section under the shower now is far easier than after the tile is down.
Low curb or no curb
A standard shower has a curb, a small wall at the entry that keeps water in. A low curb is the easy upgrade. A curbless shower, where the bathroom floor runs straight into the shower, needs the shower area to sit lower than the rest of the floor so water still runs to the drain.
- Low curb: works on any floor, smallest change to the existing structure
- Curbless on a raised floor: the floor framing is lowered or reworked in the shower area
- Curbless on a slab: the slab is recessed, which adds concrete work and inspection
- Linear drain: lets a curbless floor slope one direction, helpful in narrow alcoves
Should the house keep one tub
If the home has two bathrooms, converting one and leaving a tub in the other covers both small children and anyone who prefers to shower standing up. If the hall bath is the only full bath in the house, think about who will live there in five years before removing the only tub. This is a judgment call, not a rule, and we will tell you plainly what we would do in your house.
Permit and review time
Because the conversion changes the drain, the valve and the waterproofing, the City expects a permit. As a non-structural bathroom remodel it falls in the group the City reviews in up to one week. A permit requirement also means an unlicensed handyman cannot legally take the job, even for less than $1,000, under the rule CSLB explained in its AB 2622 bulletin.
Questions homeowners ask
Is a tub-to-shower conversion a good idea for aging in place?
It is usually the single most useful change. Stepping over a tub wall is where many falls start. A low or curbless entry, a built-in bench or a spot for a shower seat, a handheld shower on a slide bar, and wood blocking inside the walls for grab bars make the shower usable for years longer. The accessible bathroom page goes further.
How long does a conversion take?
Less than a full remodel, because only the tub area is rebuilt. The City review is up to one week. On site, the pace is set by the pan curing, the tile and the glass, which is measured after tile is set. Your contract lists approximate start and finish dates.
Can the new shower be bigger than the old tub?
Within the alcove the shower can be as long as the tub was, and taking a linen closet or a vanity section next to it can widen it. Going past the room's walls makes it a different project with a longer review.
Glass door or curtain?
Either works. A curtain costs little and suits a curbless shower where a door would block a walker. A fixed glass panel or a hinged door keeps water in better and is measured after the tile is finished.
Sources
Facts on this page last verified: .
- City of Simi Valley Building and Safety, Online Permit Submittal Instructions: https://www.simivalley.org/departments/environmental-services/building-safety-division/online-permit-submittal-instructions (2026-10-05)
- CSLB Industry Bulletin #24-07, December 31, 2024: minor work limit rises to $1,000 (AB 2622): https://www.cslb.ca.gov/Resources/IndustryBulletins/2024/AB%202622%20Implementation.FINAL.pdf (2026-10-05)
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