# Extending concrete pond



## GraemeVW (11 Jul 2022)

I built this raised pond about 4 years ago. It was a raised bed, but I got bored. It's about 3'x2'x2', ish. Just has some hardy fancy goldfish in it.
My neighbour is planning an extension and some of this hedge might be getting replaced with a wall so im now considering extending the pond. I wouldnt do it with the hedge there as maintenance would be a pain, but if the hedge goes, maybe I will.

The pond was dig, then I built it inside with fiber reinforced concrete, painted.

I suspect I'm clutching at straws, bit is there any way to extend a concrete pond, without it leaking? Or, as I suspect, is it all out and go again? Not sure I'd want to do it in liner. Could maybe be convinced to do it in fiberglass maybe.








Plan would be to extend it about as far as that struggling lavender plant and have that end all natural looking with maybe even a small beach.


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## GraemeVW (11 Jul 2022)

Getting a bit carried away now.
This is the view onto the garden




Always gets a bit hammered this, alot of it is backfield clay from when I built the sunken workshop to the left and levelled the garden out with the spoil.

I'm now thinking I could go the full width with the pond, have it like a canal on the left, on the right make it more natural beach.
Have a central, flat, decked bridge to get into the garden.
Filters could go in the workshop on the left.
Bad paint rendition




Would probably do it all in concrete, it seems cheapest/easiest to me. Unless anyone can talk me into otherwise.

Could even put a window in the front wall on the right.

Why do things always get out of hand 🙄

If I went this far, there would be no point trying to extend the original concrete, I'd just take it all out.
But if I just extend it a smaller amount, it would still be handy to know if it's possible.


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## sparkyweasel (12 Jul 2022)

I am given to understand it's difficult to extend a concrete pond. 
I would consider building a new pond adjecent to the existing one as an easier option. If you build the new one a bit lower, you could link them with a waterfall. Just another idea for you.


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## GraemeVW (12 Jul 2022)

Yes, I've been reading a bit, some folk think it's possible, most dont.


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## martin-green (12 Jul 2022)

It's the join in concrete that is the problem. People have tried, but always end up wishing they hadn't started in the first place. Even if it looks ok at first, the additional concrete will contract, causing a leak.

If you want a bigger pond, you should demolish everything you have and start again, but nothing says you can't use a liner, its easier and cheaper than concrete.


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## GraemeVW (12 Jul 2022)

martin-green said:


> It's the join in concrete that is the problem. People have tried, but always end up wishing they hadn't started in the first place. Even if it looks ok at first, the additional concrete will contract, causing a leak.
> 
> If you want a bigger pond, you should demolish everything you have and start again, but nothing says you can't use a liner, its easier and cheaper than concrete.


Yes, the joint will always be the problem.
I have read about reinforcing the join, and then once it's all set, V ing it out and injecting resin, but I think will always be a risk.

I don't like liners. Did my parents pond with a liner many years ago. It can be a pain. Concrete is cheap and I can do it myself easy enough.


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## not called Bob (16 Jul 2022)

thin layer of insulation foam over the new and old sides/base to allow some settlement and then grp onto that


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## martin-green (18 Jul 2022)

I had no idea how much a "GRP Kit" costs so I googled and the smallest I found is £100  (But it does say covers 2 sq M, but then there will be 2 sides and a bottom to cover) and what insulation foam?
I can not help but think that GRP is too expensive .

If it were me (and it isn't) I would want it to be 100% leakproof, so I would still demolish the whole lot and make it bigger

One thing is for sure, when you have a pond/pool no matter its size after a while you will want to make a bigger one.


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## GraemeVW (18 Jul 2022)

I don't think buying a grp kit would be the way. I know plenty of roofers, buying grp materials wouldn't be a problem.

At the moment, of I extend to the size I'm thinking, I'll either rip it all out and do the whole new one in concrete, or if I use fiberglass, maybe I can leave part of the old concrete in. I'll have to have a read up on fiberglass ponds.


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## foxfish (18 Jul 2022)

Fiberglass over cement is the way to go, where I live it would cost you around £60 a square meter to have it done or around £35 - 40 a square meter for the DIY materials.
However polllester resin is oil based and going up in price rapidly.
Not to  difficult  to apply once you are experienced but it could turn very messy and develop  into an expensive mistake if it is your first time!


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## GraemeVW (18 Jul 2022)

Over done alot of similar work but with fiberglass matting and decothane (a liquid rubber), so have some experience. Won't use that for the pond though, no idea if it would be safe!
I have friends experienced in fiberglass though.
If I fiberglass over concrete I could even do the concrete in sections, with rebar bridging the joints. 

In reality, I'll probably dig it, do it I  finer reinforced concrete like the small pond, and see how it goes. I'll then make a decision if I paint, or fiberglass, over the concrete.

It will be a while yet though as it will be dependent on what happens with the neighbours extension.


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## dw1305 (18 Jul 2022)

Hi all,


foxfish said:


> Fiberglass over cement is the way to go.





GraemeVW said:


> Won't use that for the pond though, no idea if it would be safe!


@foxfish is too modest to tell you this, but he is a pretty reliable source.

He had a Koi Pond business that was <"so successful"> that he now owns <"half of Guernsey">.

cheers Darrel


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