Durock concrete board instead of plywood.

[rodger]

I am building a 675 with glass sides and plywood bottom (thanks Joey) and someone on the local forum suggested I go with Durock instead of plywood for the floor. The pluses to that are obvious, no rot ever. I can still use the pond armor on it. Can be cut drilled and screwed. My concern is will it be to brittle and possibly crack on me? Can I cover the seam I will have with fiberglass? If not, how would I seal the seam? I did a search and didn't find any reference to it being used like this. Maybe someone in construction that works with it could give me some input.
Thanks
Rodger

 

[jworth]

I would be worried that the Durock would tend to crumble under any sorts of pressure points as to where the plywood would not. The worst that could happen with plywood is rot and bend. With durock you have to worry about complete failure.

 

[coolkeith]

I've used it for building countertops and laying tile. You'd still need to use a plywood subfloor for the backerboard. Cement boards have great compact strength, but have little tensile strength. It will crack/break if it's not fully supported. Handle the sheets with care.

Anyways, I do like the idea of using cement board on plywood tanks, as it adds a rot proof barrier over the plywood.

TheFishGuy lined his 1000+ gallon plywood tank with cement board and it's been running for about 7 years now. He used Pond Armor to seal it the 2nd time, then used silicone over all the seams. He probably should of used fiberglass and resin on all the seams, before he applied the Pond Armor, but his way worked nevertheless. Google search his build, it was quite epic, and the 1st of it's kind.

 

[jsc]

TheFishGuy used Hardibacker. That will work.
I dont think Durock will, and it is next to impossible to get clean cuts!

 

[coolkeith]

TheFishGuy used Hardibacker. That will work.
I dont think Durock will, and it is next to impossible to get clean cuts!

Use a circular saw with a carbide tipped blade. Wear a good respirator too.

 

[godog427]

Concrete board is very brittle similar to drywall, I don't think any type of fiberglass is going to help it support weight.

 

[wantingmore]

I've used both in the past setting tile and if your going to try it I would definatly go with hardibacker over a standard cement board. It's not brittle, has great rot resistance but I would still use a plywood backer for extra support because it does have a bit of flex.


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[charliemac]

have done the durarock lining thing before, but as thefishguy did lots of fiber glass resin( marine grade is a good idea)

 

[Drstrangelove]

Yea, this sounds like a nice option when building a tank as a liner (water tight barrier over the walls or floor), but not as the actual floor or wall. Pretty nifty idea though.

 

[CJH]

have done the durarock lining thing before, but as thefishguy did lots of fiber glass resin( marine grade is a good idea)

I don't believe TheFishGuy used any polyester (aka "fiberglass") resin on his build. As I recall he started with Drylok and then later topcoated that with Pond Armor? That's a long thread so I don't want to go check.