When building a tile shower pan it is important to start with a floor that slopes to the drain. The slope is built with a mortar bed on top of a vapor barrier to eliminate the possibility of water damaging the wood structure of your home. This article teaches you how to build a mortar shower pan for tile. Mortar has everything that concrete has in it except for the stones, mortar is made from sand and cement.
There are other products and systems that have been developed in recent years. They include sloped foam floors coated with a water proof membrane and then tiled.
brief how to
In this article, you will find information about:
The shower pan must be framed properly to support the pan liner and cement installation. Use a 2x8 or larger board placed on edge between each stud on the shower side of the wall. It does not need to be pretty, just be sure it is flush with the face of the wall. As a safety precaution you should stuff a loose rag down the drain so that any tools or cement you drop down the drain will be easily retrievable while you are building the tile shower pan.
Using the staple gun, install building paper on the floor and up to the top of the shower pan blocking. This is to keep the mortar and any moisture it may hold from touching the wood.
Install expanded wire mesh on the entire floor of the shower with staples. Cut out the area around the drain large enough to put the drain assembly thru it.
The drain assembly comes in two major parts, an lower end and upper end. Separate the upper and lower ends of the drain assembly from each other and attach the lower end to the drain pipe. The top of the lower end of the drain assembly should be no more than 3/8" to 1/2 inch above the wood floor.
A clamping shower pan drain assembly sits off the floor about 1/4". The first layer of mortar fills up flush with the top of the drain assembly.
Mixing Mortar: Pre bagged mortar is the best option for building a single shower pan. It comes with additives that make it very strong. It has 7000 psi when mixed with water. You do not need to mix an additive with it. Additives or modifiers will only make it harder to work with.
You will be installing two layers of mortar with a PVC liner in between them, just like two layers of cake with frosting between them. The first layer of mortar is embedded into the wire mesh and slopes from the drain upward toward the perimeter walls.
Start at the drain by making it level with the top of the lower end of the drain assembly which should be no more than 1/4" above the wood floor and sloping it up and away from the drain at about 1/4" per foot towards the walls.
Find the wall or corner farthest from the drain and find the height of the mortar at that corner with the 1/4" per foot slope. Make this level line all the way around the shower and install the mortar to this line all the way around the shower. Your slope may be greater in some areas of the shower but you will have a level line to start your all tile at later on.
Make sure the mortar floor slopes from the wall to the drain and has no bumps or dips in it. Make a straight line around the perimeter of the tile shower pan so you know how deep to trowel and pack the mortar. Since you are putting 1/4" per foot slope the following thickness of boards will work. Always round up.
Mix the mortar, place it on the wire mesh and form the slope using a trowel and a piece of wood cut approximately long enough to reach from the mark around the perimeter to the top of the drain assembly.
Let the mortar set for a day to harden. After 24 hours the mortar will still be green and you will be able to chip it and scratch it, this is normal. You can work on it in this state, just be careful with it, ie. Don't hit it with a hammer or drop heavy objects on it or cut it with a utility knife.
Let the pvc shower pan liner run up the walls above the 2x8 blocks around the perimeter. Make sure it goes over the curb at the shower entry and down to the floor in front of the curb. Feel for the bolts at the drain and use the utility knife to cut a X over each bolt. Then press the PVC liner down over the bolts.
Locate the drain between the bolts by pressing down in the center of the drain. This will reveal where the edges of the drain are.
Cut the PVC liner out around the drain, about a 2 inch circle.
If there are weep holes on the flange you will need to cut out around them so the water will be able to flow past the liner and into the drain. Each model of tile shower pan drains is different so study yours and make sure the water will run from off the top of the PVC liner and into the shower drain.
Attach the PVC liner to the Drain using 100% silicone sealant. Only apply sealant under the PVC liner and on top of the Drain Clamping Assembly. DO NOT PUT SEALANT ON TOP OF THE PVC LINER. After the sealant is on you will install the top of the Drain Clamping Assembly by bolting it to the bottom. This will sandwich the PVC pan liner which forms a waterproof seal.
The inside corners will have excess liner bunched up because of the two adjacent walls. Make a nice fold to one wall or the other and temporarily staple the top into the closest stud, so you don't have a hole down by the floor.
You can transfer the fold to the outside and use a "grabber screw" to hold it in place. Just make sure the screw is at least 4 inch's above the top of the shower pan deck.
The shower curb is a little trickier because of the different types of folds around the curb. This technique cuts the pvc liner at the top of the curb and not near the shower floor. Cut the liner on the lines shown below. double check your cuts before you cut to make sure it will fold in the right way after it is cut. Marking the liner with a permanent marker where you will cut helps to visualize the cuts.
After cutting the liner it will lay down and fold as shown below.
Tuck the fold behind the wall flap for a cleaner install and to allow the patch to have a flat surface to adhere to.
For the outside corners, on the curb to the shower entry you can either install a pre-formed corner or make a patch using scrap pieces of pvc pan liner as shown here. You can purchase a outside corner and liquid cement to weld it to the PVC liner where you purchased the PVC pan liner.
Creating a liner patch from a scrap piece of liner, cut a single line from about the center to an outer edge so that two flaps are hanging off.
Apply glue to both pieces of pvc liner. Let one flap sit on top of the curb and the other flap run down beside the curb to the shower floor.
Let it dry. It is always better to have the patch a little larger.
Finished and sealed shower pan liner! Ready for the cement backer board and wire mesh.
Install 1/2 inch thick cement backer board on the walls, 1/2 inch makes it the same thickness as any adjacent drywall. Start by leaving a 1/2" gap between the cement mortar shower pan and the edge of the cement board. I use a scrap piece of cement board as a temporary spacer to hold the cement board off the floor. Install screws in the center of the panel first and work your way toward the edges. Drive the screws so that the heads are flush with the surface of the panel and make sure the panels have good contact with the wall studs. For more information on installing cement board on walls read the article: How to Install Cement Backer Board on Shower Walls
Before installing the final layer of mortar on the shower pan you will need to install expanded wire mesh on the shower curb, over the PVC pan liner. The wire mesh will cover the entire curb from the inside of the shower pan at the top of the mortar floor over the top of the curb and down to the bathroom floor. Make it fit snug and only put staples on the bathroom side, OUTSIDE, of the curb, (so you don't make holes in the liner on the wet side). The inside will be held in place by the second layer of the mortar. You can overlap joints in the expanded metal by 6 inches or so if you need to use more than one piece.
Before it installing the mortar on the top of the PVC liner you will need to protect the weep holes on the drain. There are three holes, next to the bolts that attach the top to the bottom of the drain assembly. Use tile spacers or pea gravel or some other thing that you can remove later to keep mortar from getting into the weep holes.
Set the drain so that the top of it is 1-1/4 inch from the top of the PVC liner. (Make sure the top of the drain has enough turns to back it off high enough to accommodate the tile and thin set, another 1/2 inch, when the tile is laid on top of the mortar).
Figure out the slope and use a pencil to make a level mark around the perimeter walls to mark the depth of the mortar. You will slope the mortar from this line to the shower drain. Provide a 1/4" slope per foot just like you did for the mortar bed under the pvc liner.
Mix the mortar using water (do not use latex modifier because it makes it hard to get a good level floor because it becomes too sticky), and pretty dry almost like cake after it has been cooked. You should be able to make a mud ball in your hand and when you open your hand the ball stays in tact and you don't have moisture or parts of the mud stuck to your hand.
Place the deck mud in the shower pan.
Create the screed line around the edges by leveling the deck mud along the line that was drawn earlier. When you level along the walls you will have less of a slope in the corners because they are farther away from the drain but you want a level mortar line along the walls so the tile sets level against the shower floor.
Pack mortar around the drain over the top of the tile spacers.
The metal lath is held in place by the staples on the outside of the shower and by the mortar on the inside of the shower. The mortar bed for the shower pan is complete.
After the floor is finished you will Install mortar over the metal lath and PVC Liner on the curb. Build up the curb by pressing the mortar into the expanded metal on the curb building it up to 1" thick on the top and 1/2" thickness on the sides. Make it smooth and straight, remember you are going to install tile on top of this and it.
Use two trowels together to form nice tight square edges.
The top of the shower pan curb is usually about 1" and slopes slightly into the shower so water will run back into the shower. The sides of the curb need to be about 1/2" so they can line up with drywall on the outside and the cement board on the inside. Then the tile can overlap the joint between the shower curb and the drywall or cement board butting up to the curb, this allows the tile to overlap the joint to create a finished look.
The shower floor and curb complete and ready for tile.
Unscrew the shower drain 1/2" or to the height of the top of the tile. It should be about 1/16" below the top of the tile when finished so you don't stub your toe on it.
Let it set for a day and start installing your tile.
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