how flush to make screws for hardibacker - Ceramic Tile Advice Forums

gadjtguy · 05-25-2002, 11:44 AM

How flush do I really have to get those hardibacker screws in the 1/4" hardibacker board? They are supposed to "cut" themselves flush with the top surface. But most do not get perfectly flush. I even pre-drilled the holes to help the situation.

I plan on laying 12" - 13" floor tiles which would require a pretty thick mortar bed, right?

Would 1/16" be fine?

Thanks for you reply

Rick

Bud Cline · 05-25-2002, 12:10 PM

12-13 inch tiles require a suitable bed. This bed would be determined by the size trowel used to apply (comb) the thinset.

Fastener heads that are sticking up above the surface of the substrate could cause some lippage in the installation.

I wouldn't think 1/16" would be a problem but in my opinion "no more" than 1/16" should be allowed.

See...this is one of my many complaints about the suitability of the product Hardibacker. I personally believe Hardibacker is not a good product for a tile underlayment. For many reasons!!!

Bri · 05-25-2002, 01:34 PM

I'll tell you what I do, when I can't get the heads to seat in the board...I go the caveman route..and HIT THEM WITH A HAMMER. Works for me!

gadjtguy · 05-25-2002, 01:52 PM

Thanks for your input. I think I figures out the trick to getting most of them flush. Speed is the key. Make sure your drill is at full speed as the head hits the surface.

As a woodworker, my instinct is to slow down at the end of driving a screw in. That doesn't work well with this stuff.

Thanks again.

Sonnie Layne · 05-26-2002, 02:22 PM

you are exactly right, if you use a slower speed, you'll have to back the screw a bit and re-drive it home. This is where you'll find out if you have good bits. They can sure break off doing this.

Louie · 05-28-2002, 09:06 PM

What I found real handy was in having the type of drill that you can adjust the torque. Using this type of drill you can adjust when it starts slipping and not drilling. Adjusting it might take a couple of screws but once you have it set right it will drive them flush because of the ratchet effect it drills them in. It worked for me. good luck Gadjtguy.

DavidT · 05-29-2002, 08:42 AM

I also just found recently that there are some of the CBU screws that have ridges on the back of the head so it helps them to drive flush. I just threw away the ones that I had that didn't have that feature. Made life a little easier. Something to check.

diemeto · 05-29-2002, 08:51 AM

make sure what ever screws you use have the proper coating as CBU is generally corrosive to normal metal screws

Bud Cline · 05-29-2002, 05:09 PM

A GOOD CBU screw has many features.

Corrosive resistant, (coated)
pierce point for stabbing into board,
square tip for drilling cement board,
hi-lo threads for gripping, (two sets of threads)
head-gafs for clearing the "set",
wide head for better holding power,
square drive.

See....a screw is not necessarily always just a screw!

John Bridge · 05-29-2002, 05:11 PM

A rose by any other name is yet a rose.

Joe · 05-31-2002, 09:42 AM

OK John, now you've gone too far. I thought this was a classy forum. The Brits are weeping and hugging each other while the earth trembles as Shakespeare turns in his grave. Imagine, combining a line from Romeo and Juliet with Gertrude Stein!

John Bridge · 05-31-2002, 11:15 AM

Uh, which part is Shakespeare?

Tom · 06-05-2002, 07:09 PM

Use square drive coated decking screws and you won't have a problem. Screws don't pull through Hardibacker as easily as they do with CBU's.

Bud Cline · 06-05-2002, 08:50 PM

QUESTION!

Are deck screws alkaline resistant?

Tom · 06-05-2002, 09:11 PM

Yes

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