A question about nailing 1/4" HardieBacker to a subfloor

[TomYoung]

Hi all:

I've sent this message to the HardieBacker folks but I thought I'd also ask here, just in case.

I'm a homeowner putting down HardieBacker as part of a bathroom floor tiling project.

I've read the "Floor Installation" instruction which states "Use the fastener pattern as a guide" to placing fasteners. The fastener pattern is, I assume, the slightly depressed circles in the field and the slightly depressed 3/4 circles and elongated circles on the edges of the product. However, while there's a pattern of elongated circles about 8" on center along one long edge of the board, there's no similar nailing pattern on the opposite long edge. The nearest fastener pattern to this edge are field spots about 5 1/4" away from the edge.

I would think all edges would have fasteners nearby, but that's not being indicated by the fastener pattern. Is this correct, that no fasteners closer that 5" or so are needed along one long edge while the other edge has fasteners much closer than that?

Thanks.

[Pat]

I think the position of the pattern can vary. Just use the pattern as a guide for spacing and put the fasteners on the edge and every 8 inches or so everywhere else. Use glue or thinset underneath before fastening.

[keith]

The "fastener pattern" on the HardiBacker I used was printed in blue ink.

There is nothing magic about the pattern. I'd fasten it along the edge, perphaps 1" in. I'd also try to hit the floor joists. One more thing, I didn't think the 1/4" stuff was for floors. I used 1/2". As the other poster said, make sure you use something under it (thinset is recommended).

[TomYoung]

The HardiBacker folks *do* recommend using the 1/4" board on floors, reserving the 1/2" thickness for situations where you want the extra thickness to achieve level with adjacent floors. I got a reply from James Hardie regarding the fastener pattern and they confirm that all sides of the board should have perimeter fasteners 8" on center. They also said the fastener pattern sometimes gets omitted in the manufacturing process, which surprised me.

Thanks to all for your responses.

Tom Young

[keith]

They've changed their minds then. When I did the bathrooms in my previous house they only recommended the 1/4" backer on walls where there was already a stiff substrate, like plywood. That's good to know.

[Jules Richardson]

Yeah, I think mine (bought earlier this year) came with some notes that said exactly that (or possibly I read it on their website). It also came with no pattern on the board - I just used screws on 6" spacings (and around 1.5" in on each edge).

cheers

Jules

[Mikepier]

You can use 1/4" on the floor as long as the sub-floor + plywood underneath is thick enough. In my case I had 3/4" subfloor, and on top of that 1/2" plywood, plus the 1/4" Hardi. Also remember to thinset the Hardi to the floor.