Step 1: Find the Underfloor Joists
The first thing you do need to do is know where the underfloor joists are, to find this out you will need to lift the floorboards up. Once you know where they are, draw a pencil line where the underfloor joist is positioned. This will help to make sure you know where to position the tray correctly.
Step 2: Position the Shower Tray
After making sure the area you have chosen to place the shower tray is level, you can position it with the 90-degree angle flush to the walls. Then with your pencil, outline the shower tray's waste hole onto the floor, as well as drawing a line 8mm from the floor, along both walls. This is to help you to know the depth of your mortar placement.
Step 3: Cut the Shower Tray Waste Hole
Remove the shower tray and using the outlines cut out the space you will need for the shower tray waste. When you have cut out the relevant space, check that the waste trap fits easily into the hole. A jig saw can be used to make the hole a little bigger if the fit is too snug.
Step 4: Prepare Mortar
First, you need to apply a waterproof sealant to the area where the shower tray will sit. The mixture you should use to make your mortar should be 5:1. This means one part cement to five parts sand. You also need to create a thick mix which you will apply as a base for your shower tray, prior to install. This helps to make sure the base is supported, stable and level at all points.
Step 5: Apply the Mortar
Now you can start to apply the mortar to the chosen area. Make sure to level off your mortar at the 8mm line that you measured before. When the bed of mortar is level, you can place the shower tray into the correct position. Make sure to peel the plastic covering off the wall facing sides of the tray before placing. Secure the tray with tape along the top edge.
Step 6: Fitting the Shower Tray
As the mortar is now laid it is more difficult to lift and place the shower tray in position with the required degree of accuracy. This is when glass suction lifters become essential, but make sure you give your shower base a test lift before allowing the lifters to the full weight. Once the shower tray is in position and is level use a small trowel to remove excess mortar from the base. Then leave it for 24 hours to set. When it is set apply silicone sealant around the edges so where the shower tray meets the wall. Fill in any gaps.