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Unread 11-08-2004, 09:05 AM   #1
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Join Date: Nov 2004
Location: Florida
Posts: 6
Raised screws

I am new to installing backerboard. My project is an entrance
foyer of about 50 sq ft. The slate install in early 70's came up
after the installation of a new entrance door. We are replacing
same with 12 x 12 ceramic tile. The floor is pier and beam with
1 x diaganol planking that is then covered with exterior grade

The flooring guy at a large home improvement store recommended
1/4 inch Rhin Board over thinset. He sold me Hillman ceramic coated,
self countersinking screws, 8 x 1-1/4, sharp point, high-low thread, specifically labeled for "cement board".

I started by cutting the Rhino board to fit the foyer, leaving room for a
1/8 inch gap between boards and a 1/4 inch gap at the walls. I mixed
up some thin set and put the first 2 pieces down (using a square notched
1/4 inch trowel). But every screw I put in would only countersink part
of the head, leaving each one raise just enough to put your thumbnail
under the head. I changed bits often (#2 phillips drive). Needless to
say I need some feedback before completing the installation.

I was using a 14.4V Craftsman drill to drive the screws. So after the thinset
had hardened I went back with a corded 3/8 in drill and backed out the screws, blew away any debris, and tried to rest them. None went any further
into the Rhino board than they had originally.

I think I can still set tile on top of this by floating some thinset over the raised heads, but I am extremly worried that the backerboard is well secured
to the subfloor. Any advice?

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Unread 11-08-2004, 10:53 AM   #2
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Jim, it the screw heads are flush to within 1/16" of the surface, you're good to go. If not, remove them, countersink the CBU, and reset them. If you have to go through that much trouble, either get square drive screws or use hot dipped galvanized roofing nails instead of screws. Phillips head screws are hard to get enough torque on them before they "cam out". You really gotta lean on the drill, and keep the speed up as you drive them home.
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Unread 11-08-2004, 10:53 AM   #3
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Welcome. The guys here are excellent at helping you with your tile and mud projects. I guess we're continuing this from the dyi.com forum! The nice thing about here is you get quick and friendly advice. The guys here are big on knowing who you are, and the specifics of your project. They also like project pics, and lots of Q and A so there's no confusion and they can give the best advice.

Remember that thinset under the backerboard is really to eliminate any voids or shifting under the backerboard, to essentially eliminate any movement. You're not really setting the board onto the subfloor, although that is a nice side effect. As long as you didn't wait too long to drive your screws (when the thinset was still wet), or you used the same screw holes without stripping them you'll be fine. Another way to say it is if you waited for the thinset to set up, and then used your screws in different places you might have cracked the thinset under the board, which means you may have to pull it up and start over.

Does it pop and creak when you walk over it? Are there areas where the board gives?
* Corey Graham - Molly is now 6yrs old and started school this year! Morgan (my 3yr old son) thinks papa setting tile looks funny
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Unread 11-08-2004, 11:14 AM   #4
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I gave up on screws years ago.

They cam out, e.g., strip out.

They back off, e.g., when on the final quarter inch of sinking, they actually back out the backerboard. In other words, the backerboard lifts off the substrate. I don't know why it does this, but it does.

You can't them in longer increments.

So we use stupid galvinized nails.
"Sir, I May Be Drunk, But You're Crazy, and I'll Be Sober Tomorrow"
WC Fields, "Its a Gift" 1934
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Unread 11-08-2004, 11:30 AM   #5
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Raised screws

Hi Cobalt,

Yes this is a continuation from DoItYourself forum. Thought I might get
a few more ideas as well as a little ecouragement to continue on. That
seems to have worked. I'll lay the rest of the backerboard today.

To answer your questions, I did not try to reset the screws until the
thinset had cured for over 24 hours. No new screw locations. What's
down seems to be solid. No creaking or cracking noises. I just want
to make sure it stays that way. Seems like the general consensus is
that I can put down thin set over slightly raised heads and still believe
that the backerboard is solidly secured to the floor.

I appreciate everyone's help and advice. Its tough gaining confidence
on the first job. In the interim I finished a front porch project which
included crown molding, extending the door jambs, and putting up molded
polyurethane pilasters. It came out nice.

I'll get some photos of this project and see if I canlearn how to post them
for all to view.

Thanks again,
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Unread 11-08-2004, 05:35 PM   #6
John Bridge
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Hi Jim, Welcome aboard.

I used to help out at the Do-it-yourself board until they got some new moderators in there who thought they knew everything. Haven't been over that way in a while.

What I have to say has already been said. I've just recently completed a large bathroom where I used Hardi-backer. I used the square drive screws, and they work great. Never had any luck with the phillips heads. I've also used roofing nails.
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Unread 11-08-2004, 08:31 PM   #7
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Raised screws

Thanks John,

I just joined and already have had some positive results. I wouldn't take
anything away from DoItYourself.com, as I've gotten a lot of good info
there as well. You can never have too many sources of information.

I completed installing my backerboard today. My fiancee took a few photos, so I will come back and post them when they are available. I had a much better experience today than when I started with the first sheet of backerboard. I incorporated a lot of the advice I had gotten (from both sites). Before starting today I did use a masonary bit to prepare the countersink for each screw. Rhino board comes with "dots" printed for
screw positions (except of course where you've made a cut), which made it
easy to do this prework. I had 10 #2 phillips bits from Dewalt at hand, and used a corded drill (with no clutch I did snap 2 bits off). I used at least 7 bits today. Some seemed to work for quite a while and others seemed to
die after just a few screws. I found a tap with a hammer on each screw
helped to get it started and reduced my frustration level. I used a straight
2 x 4 (checked before startingting) and found my finished floor was pretty level. Taped the joints and for today's coutnersunk screws scraped some
thinset over them as well. All in all I'm fairly pleased.

One thing I did, that everyone might think about; I dry test fit the last sheet. Good thing. The two on either side were a liitle off when I dropped
them on the thin set, hence I needed to trim the last sheet just slightly.
Nice to find that problem before putting the thinset down.

Thanks again everyone,
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