strength of 4x4

[steven0161]

I need a little advice on the above, i have built a u shaped wall from concrete blocks that i am going to use as a base for a large fish tank.im planning on bolting some 4x4 joists to the top of this stand, the gap is 1.1 metres and the distance front to back is 70cms.

the weight of the tank will be about 600Kg. the two sides of the concrete base will be under each of the 2 side edges of the tank.

can anyone tell me how many 4x4 joists i will need to be safe ?

 

[Davey]

Think I understand what you mean

If the tank is over the walls the weak point will be the base of the tank - not the beams.

I would imagine that one would be plenty although two (one each side)would be safer (no wobble) and more asthetically pleasing.

Just spread the weight as much as possible.

 

[steven0161]

thanks for the reply, on top of the 4x4 beams there will be a 18mm sheet of marine ply to spread the weight. the 4x4 are just for support. if i put 3 (one at the front, one at the back and 1 in the middle), do you think that would be more than enough ?

 

[gcol]

As mentioned, one in the middle should be fine. The trick is to ensure that the ply is evenly supported cause glass doesn't like bending too much.

 

[fathead]

could you use concrete lintels and cap them with timber??

 

[Softus]

600kg?! For a fish tank full of water?! I'd start to be concerned about the floor underneath the brickwork.

How have you calculated this weight?

 

[gcol]

How have you calculated this weight?

I would imagine, length x width x height. He's already said that the base is 1.1 x 0.7 metres meaning that it's probably about 0.8 metres high. That works out at roughly 0.6 m3 which would be 600 kgs. Of course you'd need to add the weight of the tank too.

 

[steven0161]

the floors concrete so im not too worried about that, thanks for all the replies, much appreciated

 

[eggplant]

Hi,

I'm sure you will be fine, I have made a couple of tank stands in the past, largest was for an 800 litre tank which weighs in at about a ton when full. My construction didnt involve concrete, but mainly kitchen worktop and 2 x 2. A smaller one to hold a 4 x 2 x 18" 330 litre actually went upstairs, this was a cichlid tank and held about 200k of rock as well as the water etc, I was a little concerned about the weight upstairs but then I compared the weight to a bathtub full of wawter with 2 adults in it....

 

[Davey]

600kg is only the weight of say 7 people and the tank weight will be negligible.

Think of a party New Years Eve - loads of people jumping up and down (well if they dance like the people I know ).

Shouldn't cause any probs.

 

[steven0161]

Thanks for the replies, im putting the wood onto the wall tomorrow.

not sure if ive explained very well, just to clarify. the wall is u shaped. made from concrete blocks, 1 layer thick, and 3 bricks high. the 2 side walls will be directly under the tank supporting it. (after the wood is screwed to the brickwork), and the back wall will also be underneath the tank.

im putting 1 4x4 along the back wall (to keep everything level), then another 4x4 at the front spanning the 1.1 metre gap. and 2 more 4x4's, in the middle, (also spanning the 1.1 metre gap.)

on top of that im putting an 18mm sheet of marine ply, then some polystyrene sheets, then the tank on top.

the tank will weigh 600Kg when full.

do you think that 4 pieces of 4x4 spreading the weight in this way will be enough ?

Thanks again for the help, its much appreciated.

[/img]

 

[gcol]

do you think that 4 pieces of 4x4 spreading the weight in this way will be enough ?

Yes already.