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Concrete Pond In Edmonton A Bad Idea?


Aquaria
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Ok, I have been looking at building a Koi pond that intergrates with the deck I am building, and was just wondering what are the main reasons people do not build thier ponds out of concrete in Alberta. In my discussions I have heard of cracking an heaving, but as it will have to remain semi-heated, the heaving should not be an issue. As to cracking, it would be lined. Is there something else I am missing?

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There are probably hundreds of concrete pools in the city, but I'd bet most all of them are drained and winterized when the snow flies. I've built lots of ponds and several are left running all year, but there are still incidences caused from frost heaving around the pond. I'm not sure if there's a local koi forum - I imagine there are at least a few 12 month koi ponds around here.

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I have basic knowledge of concrete and can tell you there are a few things to consider.

  • sufficient air entrainment - property of the concrete that mitigates stress from expansion of water as it freezes within otherwise the surface will spall (common in poorly installed driveways; I'd still consider this even with a liner)
  • properly drained foundation - you need a sufficient layer of coarse sand / rock between soil and concrete otherwise you'll have frost heaving (this is why we don't place our asphalt roads directly on top of compacted soil; once again, I would not disregard this because its heated)
  • depending on the steepness of the bank or walls retaining the water I would be concerned about the potential of any pooled water freezing and exerting pressure against them

In any case, I would seek a professional's advice before going ahead with any plans - preferably a landscaper who has experience with ponds. I don't see any reasons why you couldn't do it as long as you take everything into account and install it correctly.

Edited by IronChefItaly
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I could not agree more that the prep is extremely important when it comes to pouring concrete, and I am still debating if that is the way to go, but if I do, I am thinking I will pour the walls as if I was pouring a grade beam with piles and foam under them. As I plan to heat the pond over the winter, I will also insulate under the slab to at least R-20 if not higher. The higher the better as it will assist the ground under the pond to remain unfrozen.

I know of a couple people who winter their Koi outside and from talking to them, at least one has had to dig up the pond and redo it do to heaving. Just hoping to know the issues going in.

Any chance you know of any landscapers who have installed some concrete ponds in the past?

Jason

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  • 2 weeks later...

Assuming you dig your pond deep enough that it's below the frost line and keep it heated, there's no reason to insulate under the slab. It won't freeze there anyway.

With the winters we've been having, lately, "below the frost line" would probably be China! :D

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I tend to agree with Jvision. Also, the water will carry the cold down so it doesn't matter if you dig it 4 or 5 or 6 feet to the frost line, you are moving the frost line as you dig it down.

Edited by Iceturf
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Too bad you're all in Edmonton... I would love to see/talk ponds with someone so I know a bit more for when I get my own place that will allow a pond.

I would imagine that as you dig down, the frost line would move down as well, but not as much as you are digging down. I would assume that the further you dig, the warmer the pond will stay. I would put a LOT of gravel/sand beneath the concrete to help buffer from the heaving. I'm just going off of logic though so I may be completely wrong...

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  • 2 weeks later...

The insulation under the slab helps to keep the heat in. Just like in basement construction, you insulate under the slab if you want the slab to stay warm. Think of the ground as a giant heat sink. There is also no way to build the pond so it is below the frost in Edmonton, but by it being heated with crush and foam under it, the concrete will survive the winters.

Jason

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