Leveling a monster tank

[Quo Vadis]

I am currently building a 700g tank (8'x4'x3') in my basement. (See this thread for more.) I was planning to use concrete blocks for the stand if that makes a difference.

Initially I was going to use self leveling concrete to build a pad for it, because my basement is poured concrete, and slopes to a drain, so the area the tank will occupy drops about 1.5in from one end of the 8ft length to other other. But I did not realize how expensive self-leveling concrete is, and I would need quite a bit to cover that area, deep enough. So then I was considering normal concrete, but because the tank is going in a corner I am not sure how to build a frame that would allow me to easily level it myself, plus I do not have the equipment to mix that large an amount of concrete. In addition I feel a lot more confident in my carpentry ability for the tank than in my concrete working ability. I built my own chicken coop recently and when I was a teenager helped my dad build our horse barn, but I have never worked with concrete.

Help! This is the first thing I need to do to build the tank,I have all the other plans pretty much done and would like to finish most/all of the tank in the next few weeks because I have a lots less for my job in January.

Any other ideas on how to level either the floor under the tank or the tank/cement-block-stand itself?? Please help! I am using pond liner and plywood, so if it is a little uneven it is not as big of a deal as if it were glass but obviously with that big of a tank it has to be pretty dang close to even.

 

[justarn]

im a builder mate, you could build the block sides and centre support then lay lintels on mortar to span the gaps. then shutter the edges temporarily, use wet mortar slurry to fill the gaps in the lintels and around the shutter then pour an inch or so of self levelling mix on it, remove the shutters and done... make sure all the gaps are filled as self levelling compound will find a hole!-)
another option is a 19mm marine ply 6 sided box, glued and screwed with centre supports, my 7x3x2 is on that and it is rock solid.

 

[Quo Vadis]

You sound like you have some good ideas, but tbh I I don't understand half of it. I put my questions in your text. Thanks!

im a builder mate, you could build the block sides and centre support (Do you mean here the cement blocks I was going to use as the stand?) then lay lintels (I googled this, are lintels those metal pieces you use above windows in brick?) on mortar to span the gaps. then shutter the edges temporarily, (I have no idea what this means) use wet mortar slurry to fill the gaps in the lintels and around the shutter (don't understand this part either) then pour an inch or so of self levelling mix on it (on what), remove the shutters and done... make sure all the gaps (which gaps, where?) are filled as self leveling compound will find a hole!-)
another option is a 19mm marine ply 6 sided box, glued and screwed with centre supports, my 7x3x2 is on that and it is rock solid.

 

[Quo Vadis]

Any other ideas anyone?

 

[Drstrangelove]

I've used self leveling concrete and it didn't seem expensive. I'm calculating $100 including tax. (165 lbs @ $32 over 55 lb bag.)

You need 8' x 4' x .75" of concrete if the slope is smooth. That's 24 cubic feet, and one 55 bag will provide around 7.5 cubic feet.

If I fully understand him, I'd probably follow Justarn's approach and lay the blocks first and self level at the top, not the bottom. I've never used lintels (well past my experience) so I can't offer any help on that. If you do level at the top, you'll need to work up a form to hold it in place while it sets and to keep it from finding a way down from the top.

Shutter = concrete form work. It's typically a set of wood boards/wedges, nails/spikes, metal stringers, etc. that holds concrete in place in a particular shape while it sets.

If you mortar the lower blocks, you will still have gaps in the top blocks where they meet, and along the forms, unless you take care to fill them. If you leave any holes, you may see the concrete drip out. I'd mortar the blocks and the gaps at the forms. You can remove the forms after it's completely set. I'd use plastic if it's work, but I'm unsure if the concrete will melt it from it's chemical properties.

 

[justarn]

Thats what i meant dr, concrete lintels are reinforced concrete joists, they come in various sizes, 65mm x 200mm x 4ft would be a good size, then you will only need 3 block work piers. In between the lintels there will be gaps that leveling compound can seep through so just smear mortar in the gaps. I would use 5mm hard bourd and screw it around the top edge to form a lip (shutter) to hold the levelling compound then seal the gaps with mortar. Leveling compound is almost like water so fill every hole. You will prob get away with 25mm i.e 1 bag as long as the lintels are level.
I would suggest getting the block piers level on the first course either by cutting the blocks or having a thicker mortar bed at the low edge.

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[Drstrangelove]

You will prob get away with 25mm i.e 1 bag as long as the lintels are level.

Thanks for including this part. I have a math error in my post, and 1 bag (not 3) should be fine.

 

[justarn]

A 25kg bag covers 3m2 at 5mm... so we are both wrong lol, 1 bag per 5mm on an 8x4 platform!-) 2 bags and 10mm should do it as long as your lintels are good.