How to level this surface.

[Grumps]

Sorry about the not very obvious subject.

We have an island in our dining room. It's basically a brick built structure about 1.5m x 0.6m x 1.3m high. It has plastered and painted sides and a ceramic tiled top. Anyway...

We're going to stick an aquarium on top of this, about 600l. The tiled surface isn't completely flat, and if you pop a level on it, it'll touch in the middle, but either end there is a gap of about 2-3mm. We don't want to remove the tiles in case we need to ditch the tank, so need some way of squaring it all up.

My thought was to put a thin flexible plastic/rubber sheet on top of the tiles, then apply some form of no more nails or similar, and then a 20mm MDF board. The glue should squish out in the middle, and then set hard thus leaving a flat surface. If we ditch the tank, all we need do is lift off the MDF and plastic/rubber sheet.

What would be the best sort of glue for this, or is there a much better way? Ta.

[Who?]

Mount the tank on polystyrene tiles. The weight of the water will eventually allow the tiles to flatten off at the highest point over a long period so lessening the stress in the glass. I have seen this method at a local pet shop.

[Andy Hall]

On Wed, 28 Jun 2006 16:28:22 +0100, Grumps wrote (in article ):

I've had the same issue in the past with an aquarium of this size.

The important thing is that the aquarium is properly supported by something that will give a little. It is incorrect to attempt to level the surface to make an apparently flat firm surface and then to place the aquarium on it. There is a very high chance that the aquarium base will crack and seep water or even that it will fail catastrophically.

This is even true of aquaria that have a plastic trim around the bottom. These are OK on small tanks but on a larger one, questionnable.

A heavy load is implied here. An aquarium of this size needs to be constructed from 10-12mm glass , so it's going to be heavy before you put water, rocks and livestock in. All up, it will weigh a good 700kg.

The recommended solution is to cut a sheet of expanded polystyrene of the size of the aquarium base. I used 15mm material - it shouldn't be much less. Although this stuff appears very light and flimsy, it will take compression very well over a large surface area. As long as the surface isn't any more than 2-3mm out of flat it should be able to deal with that also, compressing slightly as required as you fill the aquarium.

You can cut and fit a trim of your choice to go around the base at the bottom.

[shaun]

Lay the tank on polystyrene tiles.

[Andy Hall]

On Wed, 28 Jun 2006 16:55:19 +0100, Who? wrote (in article ):

Too thin for an aquarium of this size, especially as there is an uneven surface ......

Principle is OK, material needs to be thicker.

[Andy Hall]

On Wed, 28 Jun 2006 17:10:09 +0100, shaun wrote (in article ):

Not thick enough for a tank of that size on a non flat surface.

[Paul Andrews]

How about two layers of tiles?

[Grumps]

Thanks. I knew about the polystyrene, but didn't know if 15mm would cater for the

2-3mm out of flat. If the surface was flatter, then could I get away with a thinner poly sheet?

[Guy King]

The message from "shaun" contains these words:

Which has the advantage of insulating the bottom of the tank so you don't get condensation.

[Guy King]

The message from Andy Hall contains these words:

So use two.

[Guy King]

The message from "Paul Andrews" contains these words:

Bloody rays. Pass the allyhat, someone.

[Andy Hall]

On Wed, 28 Jun 2006 18:48:05 +0100, Paul Andrews wrote (in article ):

Possibly.

There's no real point, though, because you can buy expanded polystyrene sheet of thicker dimension very inexpensively from DIY stores and other places

[Andy Hall]

On Wed, 28 Jun 2006 19:09:41 +0100, Grumps wrote (in article ):

12-15mm should be fine. If you were to go for flattening the surface then my concern would be how it is done and the effect of that.

For example, I think that the original suggestion of something flexible, some flexible material and MDF would not really serve to flatten the surface given the load conditions. I suspect that it would bend under pressure such that you would be faced with the same non-flat hard surface with a thin layer of polystyrene on the top.

On the other hand, if you had said that you were going to re-tile it with a solid cement and make sure that the tile surface is flat, then I think that you could probably go thinner.

I don't really see a reason not to go for a thick layer of polystyrene sheet.

- It costs very little in comparison with the aquarium and the damage that could be caused if it breaks

- It is easy to hide aesthetically.

Is there something I've missed that you want to do?

[Andy Hall]

On Wed, 28 Jun 2006 21:54:23 +0100, Guy King wrote (in article ):

No point. It's easier and cheaper to buy the sheet material of the right thickness

[Grumps]

No, that's it really. Except I've just got the spirit level on it and the surface is far worse than I thought. Max difference in levels along the long edge is 7-8mm. Max difference along the short edge is 6mm. I'd be much happier with levelling this out before the polystyrene goes on (even with

15mm stuff); but still would like to preserve the tiles. I can only think of some sort of levelling compound, but how to stop it adhereing to the tiles whilst also providing a firm base. The more I ponder about this, the more I think that the tiles have to go :-(

[Andy Hall]

On Wed, 28 Jun 2006 21:54:06 +0100, Guy King wrote (in article ):

Well it would if there was going to be any condensation. This only happens if the aquarium is cooler than the surrounding room by some margin and the air is humid

Unless one is keeping cold water marine species this is not a frequent scenario....

[Andy Hall]

On Wed, 28 Jun 2006 22:21:11 +0100, Grumps wrote (in article ):

I think so. That is too much, I feel.

To give you a guideline of what I know works.....

For an aquarium of similar size, I made three brick pillars, each a brick and a half wide. This left a cavity in the pillar of one brick depth. These were filled with concrete.

I made sure that the tops were leveled off and consistent within a couple of mm in all directions across all pillars.

On the top was placed 35mm thick oak woodblock worktop with edges routed to create the desired profile.

The worktop was supported on all three pillars without gaps and was checked for flatness afterwards - never worse than 2mm in any direction.

The polystyrene went on that.

This has been in place for over ten years, same aquarium.

I think you are right. Dump the tiles. If you want a tiled surface then I would start with two sheets of 18mm ply, firmly fixed. Make sure that the ply is properly supported all over. Tile that with a flexible adhesive and make sure that the tiles end up flat within a couple of mm. Should be possible. Don't be tempted into really flexible fillers like latex screed.

Then you can go for the polystyrene sheet and work from there.

[Who?]

Fuck the wife's ideas of saving the tiles. Remake the top and do it properly

[The Natural Philosopher]

Silicone is your friend here.

[Grumps]

Do you mean a latex screed wouldn't be any good for levelling the surface after the tiles are removed? What would be the best stuff to use? I have half a bag of quick set mortar going spare. It's easy to use and provides a smooth finish (althoug a flat finish is all that's required).

Thanks for all of your help.