Does anybody have recommendations on what is the best product for waterproofing the concrete for a large pond ? Would prefer something that can either be sprayed/painted on afterwards, but something that can be added to wet concrete would be okay.
Well made concrete is waterproof (but not vapour proof - which is irrelevant for a pond). To be well made it needs to contain no capillaries. This requires _very_ _carefull_ measurement, mixing and compacting of the cement ballast and water to ensure that there are no voids. Builders merchants sell waterproofing 'admixes' to improve the mixture. You must use only the minimum of water required to set the cement and lubricate the particles (I think the admix helps lubrication and may contain a 'drying oil' to seal micro-voids).
You might do well to study the (essentially d-i-y) methods used to construct concrete boat hulls. In fact, you need to avoid subsequent cracking, so using chicken wire reinforcement, as in boat hulls, would also be a good idea. Don't forget to cover the concrete while it's setting to prevent it drying out prematurely.
P.S. anyone remember how carefully made concrete has been shown to be strong enough to make coil springs for automotive suspension?
-- Jan
Bondaglass, Beckenham, Kent do a moisture curing urethane called G7(?). Not a clear finish though.
By "wet concrete" do you mean freshly mixed concrete being poured to form the pond, or existing solid concrete with a wet surface?
[Some of the answers received so far appear to assume the first and some the second!]
There is a product that you can buy for mixing with a render, short plastic fibres, that mean the you can make the render with much less sand, ie a lot more cement. This makes it more waterproof. You also use the type of sand that you wouldn't normally use for rendering.I can't remember which sort. A specialist Koi supplier should know about it. Karobar Koi in Bricket Wood near Watford certainly sells it. I did mine over 10 years ago and it has not even got any seepage.
Kevin
Have a look here
HTH
Nick
Well a bit of both. I've dug a huge hole in the ground (which is for a fire pump supply) and laid a bit of concrete in the bottom to see if it was watertight - which it wasn't:-(
I could dig this out if it can't be covered, and obviously I still have most of the pond to do.
This site refers to "waterproofing powder" but I can't find a supply on their site. Any ideas where I can get it from ?
Many thanks
On Thu, 7 Oct 2004 08:06:12 +0100, "stuart noble"
I thought the US was a member
Thanks - just what I need
Thanks. I was just too lazy to check
Now Russia's a member it's supposed to be G8 but together with the US I'd make it 'G7 and a bit'
cheers, Pete.
Yes, but it was cement, not concrete.
Yes, and even more, it was micro defect free cement
In message , Pete C writes
Works well does G4. Re-coated my concrete pond with the stuff last year. Pond is 15'x15', built probably about 20 years ago, the original sealer had worn off in a few places, or the render had pin holed here and there. It was losing 15-25mm of water / week, after a clean, patch up (car body filler!) and a couple of coats of G4 now holds water just fine.
How much of it did you need for this size ?
A long time ago I had to repair a concrete birdbath thingy (fairly shallow but about 5' in diameter) which was leaking water from a crack near the centre. I wire brushed it and then applied a layer of fibreglass (of which I happened to have a supply for my kit cars). It not only repaired the leak but prevented slime, bird droppings, etc. from adhering to the surface. It lasted for many years and was still good when the house was sold.
In message , G&M writes
I think is was 3 off 5l, and one 2.5l tin. ISTR the sides had 3 coats, and the bottom 2 coats.
I got mine from Bradshaws-
There's picies from a previous clean out at
I think you will find you can't use fibreglass for ponds, as the gell coat "leaches" minute ammounts of checmicls that kill fish. The Gell Coat is what makes it waterproof.
I guess this is the issue with many products, the tings you would tank your house with, generall also kill fish. The waterproofer I have has a big "kills fish" warning label on the can.
Rick
I asked the experts (
If the colourant is piscitoxic, then there may be problems.
The above is an old satellite dish cover that was sawed in half, thrown away, rescued, fiberglassed back together, with a new black gelcoat on, and an added plant shelf.
Leave it a week for it to dry fully, then change water several times over the next week before putting fish in.
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