Walk-In Shower Planning Guide

Updated September 2026 · 8 min read

A walk-in shower is the single most requested change in a bathroom remodel, and the one most likely to be planned around the wrong things. The tile gets chosen first and the waterproofing last — which is exactly backwards, because one of those decisions you'll live with and the other one you'll pay for twice.

This guide covers the decisions in the order they actually need making: size, curb, drainage, waterproofing, glass, and the details that get forgotten until the tile is already up.

What "walk-in" actually means

The term covers three quite different builds, and the price gap between them is large:

• Curbed shower. A conventional low threshold, typically 4–6 inches, that contains the water. The default, and the cheapest to build correctly.
• Low-threshold / barrier-reduced. A shallower curb, often around 2 inches, easier to step over without the structural work of going fully flat.
• Curbless (zero-entry). The floor runs flat into the shower. Beautiful, genuinely accessible, and the most demanding thing you can ask of a bathroom floor.

Most people picturing a "walk-in shower" mean a curbed shower with a glass panel instead of a tub. That's a well-trodden, well-priced job. Curbless is a different project with different structural consequences — covered below.

Size it before you design it

Showers get planned on mood boards and built in square feet. Decide the footprint first, because it constrains everything else.

Minimum sizes are set by local code and vary. Confirm with your building department rather than a blog — including this one.

The tub-to-shower conversion is the value play

If you have a standard alcove tub, its footprint is already a well-proportioned shower with plumbing in roughly the right place and three walls to tile against. Converting it is one of the few bathroom changes that improves daily life substantially without moving anything expensive.

The one caution: if this is your only full bathroom, think hard before removing the last tub in the house. It's a resale consideration and a small-children consideration, and it's much cheaper to weigh now than to reverse later.

Drainage and slope: the part that's invisible and decisive

Water has to reach the drain by gravity alone. The floor is built with a deliberate slope — commonly around a quarter-inch per foot — toward the drain. Get this wrong and you get standing water, which is a permanent, visible reminder in a brand-new shower.

Two drain approaches:

• Center point drain. The floor slopes from all four sides toward the middle. Requires small tile or mosaic on the floor, because the tile has to follow a compound slope. Cheapest and most common.
• Linear drain. A long channel, usually along one wall or at the entry. The floor slopes in one direction only, which means large-format tile can be used on the shower floor. Costs more, looks cleaner, and is effectively required for a curbless build.

Waterproofing is the whole job

Tile is not waterproof. Grout is not waterproof. Cement board is not waterproof. The waterproofing is a dedicated system installed behind the tile, and it is the only thing standing between your shower and the joists.

Modern builds generally use one of:

• Sheet membrane bonded over the substrate, seams sealed — fast, consistent, easy for an inspector to see done right.
• Liquid-applied membrane rolled or troweled on in coats to a specified thickness, with reinforcing fabric at corners and changes of plane.
• Foam board systems — waterproof panels that serve as substrate and membrane together.

What matters more than the brand is that the system is used as a system: same manufacturer's corners, seams, and drain flange, installed to their instructions. Mixing components is where failures start.

This is also the number one place not to economize. A vanity can be swapped in an afternoon in eight years. A failed pan means demolishing the shower you just paid for, plus whatever the water reached on the way down.

Curbless: what it really requires

A curbless shower needs the shower floor to sit lower than the bathroom floor so the slope has somewhere to go. That depth has to come from somewhere:

• Recessing the subfloor between the joists — possible in many builds, but it is framing work and sometimes needs sistering or an engineer's opinion
• Raising the entire bathroom floor to create the drop, which then has to be transitioned at the door
• Building over a concrete slab, where the slab may need cutting for the drain line

Add a linear drain, a larger waterproofed area (water travels further with no curb to stop it), and usually a longer glass panel. Curbless typically adds meaningfully to a shower budget and is a decision to make at design time, never mid-build.

It's worth it when accessibility matters — aging in place, a wheelchair, or simply not wanting to lift a leg over a curb in twenty years. As a purely aesthetic choice it is an expensive one.

Glass: the line item nobody budgets

Shower glass surprises people more than any other selection, for two reasons. It is measured only after the tile is set, so it arrives as a late invoice. And the price range between options is enormous.

If budget is tight, a fixed panel with no door is frequently both cheaper and better-looking than a mid-range framed enclosure — provided the shower is long enough that spray doesn't reach the opening.

The details people forget

• The niche. Decide its position and size before waterproofing. It has to land between studs, be sloped slightly to drain, and be waterproofed like the rest of the shower. Retrofitting one is not a small job.
• The bench. Same rule. A bench must be built and waterproofed as part of the shower, sloped so water runs off, not into the wall.
• Valve position. Put the valve where you can reach in and start the water without standing under it. Obvious, routinely missed.
• Ventilation. A shower without a properly vented exhaust fan is a mould project with a drain. The fan must vent outside — not into the attic.
• Lighting. A shower needs its own wet-rated fixture. Relying on the room's ceiling light gives you a dark box.
• Curb height and sill. If you keep a curb, it needs a sloped, waterproofed top so water runs back in.

Planning checklist

Frequently asked questions