Shower Pan Slope and Drains: How Much Slope, and Linear vs Centre

The short answer: the common minimum is 1/4 inch of slope per foot toward the drain (LATICRETE’s HYDRO BAN instructions say the same). A centre drain needs the floor sloped from all sides into one point, which suits smaller tile. A linear drain lets the floor slope in one direction, which suits large-format tile and curbless showers.

Why slope matters

Too little slope and water sits in puddles, which means soap scum, mould and grout that never dries. Too much and the floor feels like a ramp. The slope is built into the mortar bed under the waterproofing, so it has to be right before anything else goes on.

Ahh ahh ahh! Beware of crumbly floor mud. A basic bagged sand mix that’s mixed too dry or too wet can crumble under the tile. We use LATICRETE 3701 Fortified Mortar Bed, mixed right. Why it matters. Best way? Do your research and hire a pro.

Centre drains

• The floor slopes down from every wall to one point.
• Big tile can’t bend into that shape, so it needs cuts along the slope lines, or a mosaic floor.
• Classic, reliable, and often the simplest option in a tub-to-shower swap.

Linear drains

• One long drain, usually at the back wall or at the entry.
• The floor slopes one way, like a single flat plane, so large-format tile and slabs can run straight across.
• Pairs naturally with curbless showers.
• The drain body’s flange has to sit flush with the top of the bed so the membrane can lap onto it.

Getting the slope right

The drain height comes first; the slope is measured from it out to the walls. Longer showers need a thicker bed at the far wall. On a curbless build, that extra height has to come out of the floor structure (see Curbless Shower Build).

Remember: flat and sloped aren’t opposites. A good shower floor is a perfectly flat plane that happens to be tilted.

Frequently asked questions

How much slope does a shower floor need?

The common minimum is 1/4 inch per foot toward the drain. Check the instructions for the membrane and drain you’re using.

Is a linear drain better than a centre drain?

Not better, different. Linear drains suit big tile and curbless entries. Centre drains suit mosaics and smaller showers.

Why does water pool on my shower floor?

Usually the slope is too shallow, uneven, or the drain was set too high. It’s built into the bed, so fixing it usually means redoing the floor.

How much does a linear drain cost?

I DON’T KNOW without the size, brand and finish. Ask for a quote on your specific shower.

Changing the drain is often part of a bigger bathroom renovation, from the floor structure up.

By Mike Bourdages, Burlington Tile. Last reviewed Mike to confirm review date.