"Hello, I would definitely do this myself, so I encourage you to do the same. Below are my recommended steps to apply the cement board to your existing floorboards: First, you should check that all floor boards are fitted correctly and suitable to use. If there are any loose parts or corrections needed for the existing floorboards, now is the time to make them. Ensure the floorboards are clean afterwards to be usable surface. Then the mortar bed can be set by a thin set mortar (follow manufacturer’s advice of use where possible). After this, you can begin laying cement board. You should use cement board ideally between 6mm to 12mm, depending on your needs and judgement.
Answered on 5th Mar 2019 - Member since Mar 2019 - report
When laying the boards, ensure the first board has around a quarter of an inch gap from any walls nearby. Additionally, staggering the joints will make for a stronger base for the tiles, this can be done by keeping cement board edges no more than 8 inches to the joints. The board can then be fastened to the subfloor using quarter-inch cement board screws. These have special coatings and protection for this use – other nails would insufficient as they would corrode over time, leaving them ineffective and in need of repair/replacement. You can repeat this process for all the boards until the floor has been boarded. Continue to leave quarter-inch gaps between panels and staggering the joints – as mentioned above. For the last board of each row, they can be cut; holding a drywall T-square along the cutting line and indenting using a standard utility knife along the edge. Ideally have a few deeper scores through the fibreglass layer, which will allow you to lift the panel (along the indented edge) to snap the panel backward, to break the panel’s core. This makes it much easier to then cut through the remaining fibreglass layer, to finish the cut into two pieces.
These panels can then be installed for the remaining rows, continuing with quarter inch gaps for all panel edges. You can then use self-adhesive cement board joint tape to cover the joints between all panels. This will ensure it can bear contact with cement, unlike ordinary drywall joint tape. After the tape has been applied (be sure to double check it is adhering to the cement board correctly), add a very thin layer of mortar over the joint tape with a small drywall knife. Ensure that the mortar is applied smoothly and evenly, to be flush with surrounding surfaces. After the mortar has completely cured, then you can begin with the tile installation itself. "