laying concrete for a slab ?

[Icom]

Well,my basement is just too dang un-level to set up my 75g:cry:,so I'm gonna have to lay a slab of concrete to get a level area :mad2:

Would a 4.5ft x 2ft slab , 2" thick be enough to support a loaded 75

I've never layed concrete before,so I have no idea what I need or how to do it:1zhelp:

 

[Sploke]

Why not just shim the stand?

 

[Icom]

Why not just shim the stand?

well,I tried that,but it's not a problem of the basement floor merely sloping a little this way or that way..it's like drunken sailors in 1880 poured the concrete floor,so it slopes,dips,drops,rises,rolls and then some.(floor also has a drain in the center that everything slopes toward)

I found one spot that I could get the stand pretty close,still not perfectly level,but most of the stand base isn't touching the floor;looking under the stand,the boards that run lengthwise,are off the floor a good bit;so there isn't much actual contact between the stand and the concrete if that makes sense,just the one end,most of the back,and the other shimmed side

 

[The Zigman]

Can you build a wood base for the stand to sit on?
70 gal of water will weigh about 560 pounds..plus the weight of the stand, rock, sand, etc...
It wouldn't be as simple as just pouring concrete on the floor, and you would have to wait about 3 weeks to put your aquarium on the new slab.

I would build a box out of 2x4's on edge, and plywood. Place it on the floor where you want the tank. shim it level, Then use a pencil on a block of wood, or a compass to transfer the profile of the floor onto the 2x4 frame, and cut it to match the profile of the floor..

use 2x4's around the edge, and double thickness of 3/4 ply on top (since there will not be any center bracing to support the tank, the 1 1/2 inch total thickness of the plywood will be fine.) You could use stick on floor tile to cover the base and make it look nice too!

 

[Icom]

I could,but that seems like more work/harder to do than just building a 5ft x 2ft frame,leveling the frame,and filling it with concrete. mixing and pouring the concrete seems like a simple idea to me,what do you meen it isnt as "simple to pour concrete on the floor" ??
The couple week wait for concrete to dry isn't a problem ( spring turkey season starts here Monday:grinyes:,so I'll be pre-occupied with that anyway until the middle of May or I fill tags,which-ever comes first)

 

[Sploke]

I have a footing drain in my basement too. I went out and bought about 2 dozen fender washers (large flat washers, about 1" in diameter with a very small hole in the center) and used those to fill the large gaps under the stand for my 150. A few packs of shims would do the trick also, most likely. I was using an iron stand, so it was only a matter of shimming the 6 legs rather than the entire perimeter of a wood stand, which made it easier, but I can't imagine much more than a half-inch gap at any one point over a 4 foot span, which would be easily taken up with shims. I mean, if you really feel the need to pour the concrete feel free, but there are definitely easier, cheaper and faster ways.

 

[Icom]

thats an idea with the washers. and no,there wasn't any where with gaps that big,more like 1/4" or less. I'll pick up a few more packs of shims from HD tomorrow and some washers and see if I can get the thing set good and all the spaces taken up with shims and washers and whatever..
just worried the tanks gonna crack or the stands gonna do something ,but I suppose as long as a level says its set flat,thats all that matters as long as I get as much of the stand to contact the floor somehow

I got a sheet of 1/2" styrofoam too,for a piece between tank and stand

 

[gsparsan]

Being a structural engineer, my advice will be:

If you cast a solid layer of concrete on top of the existing floor, without leaving air pockets, the concrete will be strong enough no matter what the thickness is because the load is going straight through to the existing slab. So don't worry about the new slab being strong enough.

You have to be careful about the area of stand that is actually bearing onto the concrete (irrespective of thickness). You cannot have more than 1 kg per mm2 unless its a stronger grade of concrete mixed by a proper builder. So if the stand has 4 legs and each leg does 2"x2", thats 10,000 kg in all ! Will your stand take that or not is a different matter.

You don't want to pour too thin a slab layer as it will crack out with time, even without the weight of the tank on it. Anything less than 1" will easily crack. I will go with 2" just to be on the safe side.

 

[The Zigman]

Also, the cured concrete floor will draw the moisture from the new concrete..drying it from the inside out. making it more brittle... As with tuckpointing masonry, you have to keep the old concrete damp, so the new concrete will dry and cure correctly, also you will have expansion issues, whick could crack your new slab.If you pour less than an inch or so of concrete, you could buy a bonding concrete, which has some vinyl adhesion promoters in it, to aid it in bonding to the old floor..
You could use some sort of membrane between the floor and the new slab, but this just seems exhaustive to me. If you want this to be a permanent installation, then you need to consider these issues...
just my 2 cents.

 

[stevep70]

I wouldn't use anything less that 3" of conc. w/4"x4' welded wire mesh imbedded in it and cut an inch short on each side so it doesn't come to the edges. Allow to cure for 21days and you will be ready to go. Be sure to wet the existing conc and make sure it it clean to get the best bond. I would even go so far as to spall off the top surface of the existing conc. to allow a better adhesion.