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kebwi 02-04-2010 11:23 AM

Hardibacker vs. Durock...and how to cut
What's your preference between Hardibacker and Durock?...and why? I can get both. Durock is cheaper but Hardibacker is "prettier", none of those frayed mesh edges...on the other hand, I can imagine that the rough durock might adhere better to other substances (poured cement (vermicrete in my case) behind a retaining wall or thinset for ledgestone/tile).

Any general thoughts on this. Should I choose fairly arbitrarily or are there arguments for and against?

How do you like to cut them...assuming I'm just making straight cuts? There seem to be countless possibilities: score/snap (with some special carbide blade I think), diamond blade on angle grinder, some strange uses of skil/table saws, jigsaws (presumably a toothless blade?), and at least one suggestion to just run the stuff right through my tile/brick saw like a table saw...which in some sense seems like the easiest suggestion assuming it would work with my standard cheapo blade that I used for the firebricks. I would have to remove the rubber splash flap I suppose.


egalecki 02-04-2010 11:59 AM

Re: Hardibacker vs. Durock...and how to cut
There's a scoring tool for hardibacker you should use to make straight cuts. I think they actually DON'T want you to cut it with a saw. That said, when I have to make cut outs for things like outlets, I mask up and use a rotozip to cut it, but for the straight cuts, I just use their tool.

Durock (which I tend to not use, it's too heavy for me to manipulate lots of it) can be cut with a saw, but it's horribly messy. And I'd still wear a mask.

I don't know that one product is better than the other, I just prefer the hardibacker for the nice edges and being able to score and snap it.

kebwi 02-04-2010 12:37 PM

Re: Hardibacker vs. Durock...and how to cut
My intention is to use cement board as a retaining wall to shore up a vermicrete structure. I had, in fact, fully intended to proceed without any cement board at all...perhaps wrapping the vermicrete in chickenwire after it cured, but then this cement board idea hit me. The goal is simply to support the vermicrete against lateral collapse (unlikely) and more importantly to protect the corners which would otherwise be very weak of course.

Do you think this makes any sense?

Should I use the thinner or the thicker hardibacker for this?

Will the vermicrete "glue" to the hardibacker or do I need to hold it in place? I envision a rod projecting from the hardibacker into the void were the vermicrete will be poured with a plate on the end that would would locked inside the vermicrete. I'm a little unclear how to do this. I could drill a hole in the hardibacker, then insert a long bolt and hold a plate (a washer or a tie plate) in place at the end of the bolt between two nuts. The problem is that the bolt head would protrude on the outside of the hardibacker, which might be problematic when I stucco the exterior.

Any thoughts on this crazy idea?

SCChris 02-04-2010 12:53 PM

Re: Hardibacker vs. Durock...and how to cut
I use the thicker produce of hardie backer and my reasoning is that the work to apply it and the cost are about the same but the rigidity is much better with the 1/2 inch, so flex isn't an issue what so ever. I have also used the 4 by 8 foot sheet, exterior concrete panel Hardie Panel I think it's called, thinset as a base for floor tile where I had some cracking in the concrete underneath. My reasoning here was that it gave me some isolation over any new movement that might occur.

Just my thoughts.

Wiley 02-04-2010 02:26 PM

Re: Hardibacker vs. Durock...and how to cut
2 Attachment(s)
Kebwi, if you are just going to use it for a form I would suggest using 1/8 inch fiberboard. It's alot easier to cut and you can bend it into a ring around the base of your WFO to get a start when pouring your insulation. That's what I did save that I was shaping my refractory not the insulation.
Perhaps I'm not understanding your intended use.
A picture being worth a thousand words ... here's a couple showing what I mean:

Hope it helps,

egalecki 02-04-2010 03:09 PM

Re: Hardibacker vs. Durock...and how to cut
My vermicrete was thick enough to support its own weight. I scooped up handfuls and plopped them into place- patting it like a sand castle. I brought up the walls (mine were over the blanket, which I'd covered with chicken wire) to the crown of my igloo and then started dumping the stuff on top, keeping the depth a pretty uniform 4 inches all around.

If you're after an igloo shape, I'd bag the form and just use your hands. I think there are some pictures on my thread of how the walls went up. If you really want a form, then I'd say Wiley is right. (as he frequently is!)

RTflorida 02-04-2010 03:40 PM

Re: Hardibacker vs. Durock...and how to cut
I prefer the HardiBacker. As others have said, smoother edges, no mesh, no crumbling of the edges. I have only used the 1/2" of both, so no comment on the thin stuff. As for straight cuts - I use a backer board blade in my cheapie circular saw, a lot dust but is faster than scoring, scoring and more scoring, then snapping... AND a perfectly smooth edge.


kebwi 02-04-2010 03:45 PM

Re: Hardibacker vs. Durock...and how to cut
No, with reference to my terrace thread, the idea is to secure the walls of the first terrace, a 20" high square-edged wall, which will ultimately support a little additional weight as well. The second and third terraces will probably be formed with 2" cement block, but the first terrace is too high for that.

Actually, I found concrete blocks at Lowes that are exactly 20" square, but they are expensive and I wouldn't be long enough, requiring some strange additional pieces.

I think cement board will be perfect, assuming it adheres or can be locked to the vermicrete.

Tscarborough 02-04-2010 06:06 PM

Re: Hardibacker vs. Durock...and how to cut
1/2" hardi, bonded with mortar, no mechanical fasteners needed. Mortar set the brick for the walls.


kebwi 02-04-2010 07:16 PM

Re: Hardibacker vs. Durock...and how to cut

Originally Posted by Tscarborough (Post 79635)
1/2" hardi, bonded with mortar, no mechanical fasteners needed. Mortar set the brick for the walls.

So, this idea of bounding the vermicrete pours with brick (and hardibacker). You're suggesting I mortar the brick and board to the vermicrete wall? How do I do that if I'm pouring the vermicrete into the brick and hardibacker as if they were the pour form?

...or was that never your intent? Were you think I should first form and pour the vermicrete and then, after the fact, mortar the brick up against the side of the vermicrete wall?

Sorry, I'm afraid I may have misunderstood you.

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