Installing Hardie board over a subfloor, is fairly easy, and can be done by only one person. A lot of people do not know that they are supposed to use a modified thinset underneath hardy board when installing it on the ground. Hardie board was not designed to go over a concrete or cement subfloor. Hardie board was designed to go over a plywood subfloor. The subfloor needs to be at least a 5/8 inch thick exterior grade plywood.
Many people ask, why do I have to use thinset between Hardie board in the subfloor? The reason consent is required between Hardie board of the subfloor, is to eliminate any deviations between the backer board itself and the subfloor. This decreases the probability that tile will crack, or that the grout lines will crack, causing the tile to pop up in the future.
A lot of people also wonder, can I use liquid nails to glue the Hardie board to the ground? The answer is simple, no you cannot. Hardy board requires a bonding order to ensure that the Hardie is getting a good grout to the subfloor. Liquid nails is just a general adhesive, and is not strong enough, and just will simply not bond correctly.
After the thinset has been applied to the ground and the Hardie board is laid on top, nails or screws should be applied 8 inches apart all way around the exterior edges of the Hardie board.
Then nails or screws should be applied every 8 inches apart everyhwere on the Hardie board. Do not get too close to the edges as the Hardie board will crack or break. It is important to hit the floor towards running underneath the plywood at all possible, with screws or nails.
After the Hardie board has been installed on the ground, the next step is to apply a 2 inch fiberglass mesh tape on the seams. Apply the fiberglass mesh tape on the seams, the exact same way you would do with drywall tape. But instead of using a drywall mud to float the seams, you use the modified thinset as your float. Using the fiberglass mesh tape and thinset is required, and will greatly strengthen your subfloor.