HardieBacker with Hydrodefense very difficult to drill

Question

I'm attaching a substrate onto my new shower wall. I'm using HardieBacker with HydroDefense as the substrate (it's the red kind). I was very careful to read the instructions, and I bought the accompanying Backer-On screws. They are described as "Backer-On #9 x 1-5/8-in Zinc-Plated Star-Drive Interior Cement Board Screws." They are the green-colored kind. Please see the image below:

I'm finding these screws to be very difficult to drill into the board. The description says "eliminates the need to pre-drill," but I cannot do so without pre-drilling. Also, the screws won't go in all the way so that they are flush with the board.

The manufacturer says to use "Minimum 1-1/4 in. long No. 8 by 0.375 in. head diameter, self-drilling, corrosion resistant, ribbed wafer head screws." As far as I know, that's what I'm using, and I don't see any other product that would be more appropriate.

Am I using the wrong screws? If not, what am I doing wrong here? Why is it so difficult to get these to drill in all the way so that they are flush? Hopefully someone out there has used HardieBacker with HydroDefense and knows how to screw that in without so much trouble.

I tried to contact customer service but they don't reply to email.

Answer 1

My guess is it is just more resistance than you are used to. It is probably worth taking an extra/scrap piece of the Hardiebacker, setting it flat on a couple of 2x4s on a workbench or flat surface, and practice drilling in a few screws with the ability to put your whole body weight on the drill, to get a feel for how hard you will need to push to get the screws to go in all the way. I have not installed Hardiebacker interior boards before, only Hardieplank exterior siding, and while the screws did have more resistance than normal, it wasn't too difficult once I knew how hard to actually press.

If you are using a drill instead of an impact driver, or are unfamiliar with drilling into cement fiber board (or wood that doesn't have pre-drilled holes), you may find it surprisingly difficult... you will need to exert some force even with an impact driver. See this James Hardie installation video (queued up to the screw installation part) to see how much effort the professional model is putting in even with an impact driver:

https://www.youtube.com/watch?v=83BTI1HvZ-o&t=158s

If you can borrow or rent an impact driver, though, it's worth it for an installation where you have lots of screws to install (especially if no pre-drilling needs to be done). Heck, I personally think it's worth it to buy one if you don't have one yet.