Flooring Tile - Backerboard Installation

I am having a problem with installing backerboard.

I am putting down rhino board over a plywood base. I laid out the
oards and made all the cuts. Put down thinset (for the first 2 pieces),
placed the boards, then started putting in screws (8 x 1 1/4, sharp point,
labled "cement board"). Here my problem started. I could not get the
screw heads to sink into the board. I changed bits a couple of time just
to be sure I had a good connection. I decided to stop my installation with
these 2 boards after putting in all the screws (using recommended spacing).

So I have two questions:

What should I be doing so that the screw heads sink flush (or lower) in
the Rhino Board?

What should I do about the 2 boards I have installed as each screw head
is slightly raised?

Thanks,
Jim

1. How high are the screws standing up?

2. What type of screws are you using?

My screws stood up after I put my board in. Sometimes it's debris under the screw head, and other times you have to back the screw out, and ram it back in to get them to sink. A few of them I couldnt' get in, so I took care of them with some thinset after the seams had dried.

The screws are made by Hillman, listed (on the box) as "ceramic coated, self countersinking". The box is specifically labeled as "Cement Board" screws.
They are "sharp point", #8 x 1 1/4 inch long.

Almost all the screws I put in are standing up enough to easily slip your
fingernail under the head.

Have you tried backing out the screws and re driving them? Blow out the dust and debris from underneath the head before you reset them. If you are using a cordless drill, it probably won't have enough torque to set the screws down either. As a last resort, Custom Building products allows for the use of 1 1/4" galvanized roofing nails every 6" oc for setting the backer board to the thinset and subfloor. What's your subfloor now?

Thanks for the info, I was using a cordless drill, 14.4 volt Craftsman.
I had called the store where I bought the screws and they said it
might be the driver. I have a corded 3/8" Craftsman drill I can try
with a driver bit. Will also try backing out the screws, blowing out
the debris and redriving. The store also recommended I wait the
full 24 hours for the thinset to harden before trying to reset the screws.
(Not a problem as 2 days have passed now).

If the above techniques don't help maybe I can borrow a better driver.

Thanks again,
Jim

Tilebri,

I tried the techniques everyone has suggested; a corded drill, backing out
screws removing debris and trying to set the screws again (using new screws
if the heads looked at all stripped), including using new phillips bit(s). The
screws (listed as self countersinking) still go no further into the backerboard.

The subfloor I'm working with is heavy plywood over diaganol one by boards
(a traditional floor, originating from the early 70's). The wood is in great
shape, and I have removed the thinset from the slate that was previously
laid directly on the plywood.

What should I try next? :confused: The area is not large (just 4 sheets of backerboard)
so a labor intensive solution is ok by me.

Thanks,
Jim

I'd consider leaving them alone. Drive them in, and leave them.

If they're so high you think they'll prohibit setting tile then I'd think about using thinset to flatten the area. Use some thinset and a trowel to smooth over where the heads are when you mud and tape your seams. Apply just enough so you can still see the screw head, but the mud is even with it. Then come back later when they've dried and screed another layer of thinset over the entire area to fill in the gaps. Use a set of straight edges to do it, and pull the mud diagonally across the areas that are raised to get it uniform in all directions...it'll take a couple of days, but the results can be quite nice. I had to screed my entire bathroom floor because of various flaws and waviness, and some of my screws didn't go down either. I loved the result. I used a modified thinset do do the job: Custom Building Products's VersaBond.

Thanks Cobalt. The heads aren't up very much, probably I got about
half the head depth countersunk. I was as much worried about the
backerboard being secured sufficiently to the subfloor as I was leveling
the tile. I do believe I would be able to put the tile in with just thinset over
these, but I like your suggestion of an extra layer of thin set screeded level.

Thanks again,
Jim