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I'm in the middle of a bathroom renovation, which will be tiled with large format porcelain tiles on both the floor and walls.

I put 1/4" HardiBacker on the floor, laid on top of a bed of thinset as per the installation instructions. I used the "BackerOn" coated screws that home depot sells with the HardiBacker sheets. I was not happy with how the screws tend to split or fracture the hardi, mostly around the edge even when holding back 3/4" from the sheet edge.

When I started putting 1/2" backer on the walls I switched to hot-dipped galvanized ring shank nails, 2" long, using a framing nailgun to set them. I dialed back the drive depth to leave almost all nails either flush or slightly proud of the surface, and then I tapped them flush with a hammer. I had some that broke the surface of the board though.

After completing almost the entire bathroom I then was told that I should have used roofing nails, not framing nails, due to the size of the head. What I'm concerned about is that the backer board might pull through the nail heads of the smaller diameter framing nails. They are full-round head. not clipped head, but still much smaller than a roofing nail.

Am I justified in my worry? Should I go back over and augment the nailed boards with some screws?

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I'd be inclined to add a few roofing nails in critical locations--corners, edges, etc. The nails mostly provide sheer strength, so it's unlikely that you'll see a problem.

  • Ok. I just bought a roofing nailer (for another project) and the only nails locally available are electro-galvanized, will those work? – cathode Mar 30 '15 at 20:01
  • Considering that hot-dip cracks off half the time anyway, sure. Really we're talking about a few dozen nails here. Is it worth pulling out the hoses for that? Give the ol' hammer some exercise. – isherwood Mar 30 '15 at 20:03
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Depending on what is behind your backer you need long roofing nails. I use HB 30-40 times a year and and I use the HB screws and long roofing nails. For shower walls that are a little tough I will double predrill for my backer screws. I will use a small bit for the hole then I will through each hole and use a larger bit. The larger bit I just give a tap into the board - about a 1/16th of an inch. This will allow the head to sink in well and also keep my backer from breaking on the corners. It might seem like a lot of work to double predrill but when you need to end up with flat right angles... well you will spend more time screwing and unscrewing - and backer screws are really good at pulling your board out 1/8" to drive you nuts.

Another note on the roofing nails. I strategically use them. They are fine to use, they are easy, they are faster... until you need to take the board out or add a shim. Then you are screwed.

  • I'm guessing you don't use collated screws if you predrill. You don't like 'em? Having to re-set 10% of the heads seems better than predrilling all of them. – Mazura Mar 31 '15 at 1:30
  • @Mazura I use collated. It isn't about resetting them, it is more about them causing the board to pull out. If you use 1/2" HB and one hole in the middle pulls out 1/32" by the time you are at the top it is 1/8". – DMoore Mar 31 '15 at 3:33
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I have always used a handful of nails around the perimeter, then use screws for most, but I countersink every single hole first.

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