Hardibacker board is a product of the James Hardie Company. It is a product consisting of 90% portland cement and sand. It is mold resistant and approved for wet areas. If fact most building codes are now requiring some kind of backerboard in bathrooms, kitchens are not too far behind.
One thing to keep in mind is that Hardibacker is not a structural element. If your floor flexes due to undersized joists, it will not help you until you strengthen the underlying structural issues. These types of boards only provide a way to bridge the gap between plywood and the tile, as plywood is not the best underlayment for tile.
Please read the installation instructions as I am human and may forget some things. Consider this an overview and not a guide.
First of all hardibacker is not hard to cut. To cut this board you simply score a line with a straight edge and snap it. To cut more difficult shapes you can use any power saw. Please keep in mind that power saws make a lot of dust and proper respiratory care must be taken, such as a wearing the proper mask and cutting outdoors.
Installing backerboard on the walls is very easy. In Fact if you've ever hung drywall you can hang cement board. It's just a little more difficult to cut, that's all. In fact you may want to invest in a good carbide scoring tool designed just for backerboards. It's an added expense yes, but the time and aggravation saved will more than make up for it.
I have gone directly over studs, as well as over sound wall coverings, be sure to follow the manufactures instructions as some require direct to stud application. Just be sure you use the proper screws, and screw directly into the studs. I like to use screws that are 1 5/8 inches long as long as there is a minimum of 3/4's of an inch of penetration into the stud. Countertops must use shorter screws.
You could use the shorter screws (1 1/4 inch) on the walls and floors when using 1/4 backerboard, but I just like the extra hold the longer screws give me. Make sure you use approved screws, these screws need a special coating to resist rust.
You also need to tape the seams of the backerboard with an alkali resistant tape and the same thinset you're using for the tile. These are both sold in the same aisle as the backerboard. Oh, and he boards have little marks where the screws are supposed to go, these don't always line up with your studs but they give you a good idea of the spacing required.
Now it's time to "tape" the boards. If you've ever taped drywall then this should be easy for you, you simply stick the fiberglass mesh tape to the seams and corners, then knife on your thinset. The thinset doesn't have to be perfectly flat, just make sure there are no high spots that can interfere with the tile later on.
That is pretty much the skinny on hardibacker board for he walls. It's not very difficult just be sure to get enough screws and tape the joints for a long lasting, quality job.
The floor and countertop are both the same when it comes to installation. On the floors you can use both the 1/4 inch and 1/2 inch boards. Unless you have to raise the tile up to meet another floor's height, the 1/4 inch board is fine. The countertop should only need 1/4 inch as well.
When installing the backerboard on the floor and countertop there is an extra crucial step. That step is to set the backerboard on thinset. The boards must be set and screwed into the thinset to eliminate any possibility of the backerboard moving and flexing under the weight of a person. Even if there is a minute amount of movement it will not be good for your tile floor, it will pop and the tiles will come up.
This doesn't necessarily bond the backerboard to the underlayment but give it support and eliminate any low spots
The floors must also be fiberglass taped in the seams and thinset applied over the seams, just like the walls. This ensures the floor is one unit and will move as one. If there is an area where Hardibacker will show it's weakness it's in the seams, but as long as you take the time to tape them and thinset them there is little to be concerned with.
Installing hardibacker is not difficult at all, if you follow the installation guidelines outlined by the manufacturer. Just take your time and everything will turn out good and the next step will be tile.