How to Create Correct Floor Falls to a Drain in Wet Areas
- Jax Tiling
- 1 day ago
- 3 min read
How I Create Correct Floor Falls to a Drain in Wet Areas
Creating the correct floor falls is an important part of preparing any bathroom, laundry, toilet or other wet area containing a floor drain. The purpose of the fall is to direct water toward the drain instead of allowing it to sit in low or flat areas of the finished floor.
In this guide, I’ll explain how I use a laser level and tape measure to work out the required levels and create a consistent fall toward the drain.
Establish a level reference
I begin by setting up a laser level inside the wet area. The laser projects a horizontal line around the walls, giving me one consistent reference point for the entire floor.
The position of the laser line itself is not the important measurement. What matters is that the line is level and remains in the same position while I measure different parts of the room.
I then use a tape measure to measure vertically from the laser line down to the floor. Taking all measurements from the same laser line allows me to compare the height of the perimeter with the height at the drain.
A shorter measurement means that section of the floor is higher. A longer measurement means the floor is lower.
Measure the perimeter
Next, I measure the floor level around the perimeter of the wet area. In the example shown, the measurement from the laser line to the perimeter is approximately 385 millimetres.
I check more than one location because the existing floor may not be completely level. It is important to measure near the walls, corners and doorway so I understand the starting levels across the entire room.
These perimeter readings help me decide where the finished floor needs to begin before it slopes toward the drain.
Set the drain level
I then measure from the same laser line down to the floor drain. In this example, the measurement at the drain is approximately 401 to 402 millimetres.
Because this measurement is larger than the 385-millimetre perimeter measurement, the drain is lower than the outside edge of the floor.
The difference between the measurements gives me the amount of fall:
Perimeter measurement: approximately 385 millimetres
Drain measurement: approximately 401 to 402 millimetres
Difference in height: approximately 16 to 17 millimetres
This means the floor has an approximate fall of 16 to 17 millimetres from the measured perimeter point down to the drain.
Create the floor fall
Once I have established the perimeter and drain levels, I can form the floor between those two heights.
I work from the higher perimeter level toward the lower drain level, creating a gradual and consistent slope. The surface should transition smoothly without sudden dips, humps or flat sections.
I continue checking the floor with the laser level and tape measure while forming the fall. This allows me to identify any areas that are too high or too low and adjust them before moving on to the next stage of the wet-area preparation.
The drain may not be located in the centre of the room, so the distance from each wall to the drain can be different. For this reason, I check the floor from several directions. Each section needs to meet the drain cleanly while still working with the perimeter levels and the overall layout of the room.
Check the complete wet area
After forming the floor, I take additional measurements around the room. I check the corners, walls, doorway, areas around plumbing and the surface immediately surrounding the drain.
The laser line makes it easy to compare these points using the same level reference. If a measurement does not match the intended floor height, I can correct that section before the finished surface is installed.
Careful preparation at this stage helps make the later waterproofing and tiling work more straightforward. It is much easier to correct the floor levels while preparing the substrate than to rely on the tile installation to fix major height differences.
The exact fall required for a project can depend on the wet-area design, the distance to the drain, the tiles being installed and the applicable building requirements. Always follow the relevant regulations and the instructions for the products and systems being used.
Using a laser level, accurate measurements and regular checks allows me to create a smooth floor fall that directs water toward the drain. The key is to establish the perimeter height, set the lower drain level and form a consistent transition between the two.
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