Dirt with liner vs concrete with liner vs fibreglass

[DAQ2020]

Hi. We've decided to upgrade our pond (it was a dirt hole with liner in it) to something more ambitous but we're struggling to work out what materials it should be.

We want a 3metre x 2 metre x 400mm deep pond. Inside the pond we want to put 'floating' steps. Running down the length we want two shelves we can rest plants on. Attached is what the side profile would look like.

If we go with a dirt and liner option (the simplest and cheapest option) we can't figure out how to stop the top from falling down into the shelf. This is the problem we've got now (and also the current pond is too much in the shade and getting too small for the fish)

If we go with the concrete option we think we are going to need to reinforce the sides and the bottom which is a big job.

If we go with fibreglass we're going to have to get it custom made and there isn't anyone local who does this kind of work (so I think the cost is going to be prohibitive).

If any of you were wanting to build a pond this large with floating steps and shelves how would you tackle this?

Many thanks

 

[addy1]

Welcome to our forum!

I am not sure what a floating step is or even how you make one.

 

[Lisak1]

I'm a bit confused about this floating step idea myself!

 

[Jhn]

Think if I understand the drawing right the floating steps are an appearance, when in reality there is something be it dirt/block under the liner, or whatever holding the step up.

I wouldn’t try to build the floating step under the liner out of dirt, as you are experiencing it will want to collapse down. I would either build the floating step support out of cinderblock mortared together either under or above the liner. I would probably lean towards above the liner then you can face the cinderblock with rock to hide it from sight. Under the liner is doable but it would leave a bunch of folds to deal with and you would want to grind the edges of the cinderblock down to get rid of the sharp edges.

 

[Ronfire]

The shelves can be under the liner but for the shelf in the centre just build it with Cinderblocks or even PVC pipe filled with sand if it is only to support plants and place on top of the liner. If your soil is soft and you worry about the sides caving in do the parimeter below the shelf with cinderblock to the top of the shelf level and then use a liner..Another option is to pour a concrete parimeter for the shelf and have the rest dug. Check out how the "Pond Digger " builds this system, you can google search for his informative videos.

 

[j.w]

@DAQ2020

 

[poconojoe]

Can you further explain the floating step idea?
Do you literally want them to float?

My pond is soil, then a layer of sand, underlayment, then EPDM liner.

I formed my shelves in the soil and none of the have ever collapsed.
In the past I have lifted the liner to alter the shape and size of some of the shelves, even while there is water in the pond. My point is, if you contruct the shelves out of something permanent, you won't be able to change it later.
And I'll add that owning a pond seems to be an ongoing construction. I'm always fussing with this or that.

 

[DAQ2020]

Hi - sorry for the delay in response I'm in NZ so have a time delay (while you are awake I'm sleeping ). Thanks to you all for your comments and welcomes.

Jhn has it correct - it is just an illusion of the step floating - in reality I have to have something (like the cinderblock mentioned) built up underneath. If I put in a cinderblock I will effectively be puncturing the liner and underlay to make it stable in the foundation. I worry that if I don't use concrete at least on the bottom then I won't have the strength/stability in the step. Agree Jhn doing the steps out of dirt wouldn't work.

Ronfire has suggested pvc pipe and I have seen examples of this on youtube working but only to support (as Ronfire suggests) lightweight items so in this instance it won't work as we're keen to be able to walk across these pavers.

The pond digger video was really good (thanks for the direction) and I think that idea will work for the shelf. It also then gives me the flexibility that poconojoe has suggested to rework the edges so I will follow this plan for the sides and shelf.

I think the steps in the middle and how these work with the liner is probably the most difficult part left to figure out. I've just been reading this: https://www.pondtrademag.com/floating-steps-feel-at-one-with-the-pond/ which seems to imply I either have to do the concrete option with paint or concrete/blocks with liner. The latter is more difficult according to their instructions but it would mean I keep a lot more flexibility.

There is no mention of painting the uprights that the pavers go on but I think you have to do this as I think concrete leaches out stuff that is toxic to fish. Am I right in thinking that?

I'm leaning towards going with the liner option so I think the plan would be:

Concrete shelf for putting plants on as per pond digger,
dirt sides as per pond digger,
concrete bottom as per pondtrademag,
concrete (circle) paver supports coming up out of the concrete bottom as per pondtrademag,
liner and underlay under the paver supports over the rest of the bottom and up over sides as per pondtrademag (look at image at bottom of the article to see how this works in tandem with other stages).
Paint concrete circle paver supports with paint that stops concrete leaching into pond ???

As an FYI - I also got a quote back for fibreglass - the company I spoke with said they would do it onsite as no one over here makes tanks this size - I've talked us all out of doing fibreglass because I think poconojoe is right - you want to be able to move things along the way and if I fibreglass it's going to kill the flexibility. Also it was hugely expensive ;-)

 

[Jhn]

No you don’t have to paint the concrete uprights be it cinderblock or a solid concrete pour. As they do not leach anything toxic, the lime they leach will be minimal and serve to raise the alkalinity ( kh) , which serves to stabilize the ph. This is a good thing.

I poured a concrete footer/pad for the bridge posts in my pond when I built it and have zero issues with the concrete adversely affecting the aquatic life in my pond.

 

[DAQ2020]

Hi Jhn - thanks for your comment. One less thing to think about then Did you do your pond with a liner or did you concrete the whole way?

 

[Jhn]

Used 45 ml epdm liner and just poured the footer right on the liner in a form.

 

[DAQ2020]

Okay we can do that. Sounds very similar to plan in pondtrademag - anything you'd tell the newbie to be careful of when they do the liner / concrete plan?

Do you have a link to the process you went through? I read through addy's pond link (and Addy you really do need to send through an update of photos because I'm super curious about it now too )

 

[addy1]

I read through addy's pond link (and Addy you really do need to send through an update of photos because I'm super curious about it now too )

GEEZ I will I will just need to do it.

 

[Ronfire]

if you pour concrete on top of the liner it might be a good idea to place a layer of underlay down first or a second layer of liner in that area for extra protection.

 

[DAQ2020]

Thanks Ronfire. I think this is a great idea as we are concerned about the longevity.

Okay everyone it sounds like we have a plan. Spoke to my brother in law who assures me that there is clay just below the surface and so I'm feeling a lot more confident about the plan not to concrete the sides.

We'll gather up the materials and then in the next month or two when we've built it I'll post photos back on.

Many thanks again to you all for spending the time to help us get a plan together and troubleshoot the tough areas.