A wet bed is used for installing ceramic tile for several reasons, such as when the the surface to be tiled is uneven, a slope must be created to get water to a drain, the floor needs to be raised, or the surface is an inappropriate material, such as vinyl tile Once installed properly, the wet bed will dry to the consistency of concrete, although not quite as strong as it does not contain gravel. After the bed has dried for at least 24 hours, it is ready for tile installation with thinset mortar.
Determine Needs and Prepare the Surface
Multiply the square footage by the depth in feet to get the cubic footage required. The bed should be a minimum of one to two inches deep and could be deeper depending on your needs.
Remove any material that is loose or rotten before beginning the floor prep. Smooth out or remove any irregular high spots that will interfere with the desired surface.
Nail down the roofing felt and lath if required, using a hammer. Use enough galvanized nails so there is no bounce or movement in the surface. Just before beginning to put down the cement bed, mix a slurry of cement and water and spread this over the surface. Use a broom to spread the slurry evenly. This will help ensure a good bond.
Install the Bed
Mix the sand and cement in a large commercial wheelbarrow. Using a five- or six-cubic-foot wheelbarrow, this should require a half of a bag of Portland cement to an almost full wheelbarrow. Mix the two thoroughly, using a hoe and shovel, until you have a consistent light gray mix. There should be no visible sand or cement unmixed in the wheelbarrow.
Add water slowly to the wheelbarrow and mix it thoroughly before adding more. You want a consistency like wet beach sand. Pick up a handful and make a fist. If it sticks together without being soggy, it is ready.
Shovel two parallel lines of the mixture on the floor at the approximate desired depth. The distance between the two lines will be determined by the width of the room and the length of your longest straight edge. They should be at least one foot away from the wall and at least one foot closer together than the length of your straight edge.
Tamp down on the mixture with the flat trowel to make a firm bed. Place a section of lattice strip on each line. Use the level to make sure the top of the lattice strip is even with the desired depth. Use a back-and-forth motion with the level, mashing down on the bed to get it to the correct depth.
Move the level back and forth on top of the lattice strip to achieve either a level surface or the desired fall. Once this is complete, you should have two thin lattice strips at the correct depth and either level or with the desired amount of slant.
Fill the area between and around these two strips with more of the mixture, spreading it with the shovel and trowel until you have the area covered and at a depth several inches above the lattice strip. Use the trowel to tamp it down firmly and compactly.
Force your straight edge through the mixture until it comes in contact with both of the wood strips, starting at one end of your lattice strip. Use the same sawing motion and pull the straight edge toward you to make the cement bed even with the top of the lattice strips. Use the trowel to smooth and compact the surface.
Remove the lattice strip carefully and fill these small gaps with more mixture. Smooth it out and tamp it down, using the trowel. You now have a completely smooth surface at the height you need and the desired fall. Repeat the process, starting with Step 3 backing through the room, until the entire floor is covered.