Pond Edging

Category: Miscellaneous | Posted: Thu Feb 22, 2007 9:08 am

Heavens, this seems a long dull month (actually shorter than most by a day or two).
With seedlings now swarming in the greenhouse, pricking out into plug trays as fast as I can evacuate each covered propogator, my thoughts also turn to the remaining unfinished edging to the pond, where the liner is still sticking up untrimmed, and unsightly.
Using, as Poirot says, ze leetle gray cells, I think I may have, as Baldrick says, a cunning plan...
The idea is to cast in situ cement blocks encapsulating the pond liner edge. I have been collecting 1lt plastic milk containers which, cut in half, should be the ideal size of mold for the castings.
A container is therefore cut in half, and a central slot cut half way up the two opposite narrower sides. This accepts the pond liner.
A large cement pouring hole is cut in the bottom of the container (which becomes the top), large enough to pour in cement, but retaining the container's curved edge to maintain a rigid block shape.
So, after lowering the level of water in the pond and allowing the edge area to dry out, the edge of the liner is punched with holes using a paper punch. These will act as achorage points within the cement blocks. The milk container molds are then slotted over the liner, and sit flush to the pond base. I have a built in ledge already to accept some form of cement edging.
The molds, just a few at a time, are lined up together, and filled with not too sloppy cement (or it'll just run out at the bottom) until the very edge of the liner is just about visible - this acts as a leveling indicator. The cement permeates through the holes in the liner to 'grab' it, and stop it moving once set.
Leave the cement blocks to set, remove the plastic molds, and move along to the next section and repeat until the length of edging is finished.
All then that remains to do is to skim over the tops of the castings where the liner edge is still visible.
The finished result should be a neat segmented cast cement block edge, with the liner trapped within. The blocks should be heavy enough not to shift, as each would be the weight of a house brick, plus the accumulated weight and 'liner grabbing' of all the blocks along the run.
As soon as it stops raining, I shall give it a go.
Just trialed the idea as pic below. Obviously everything needs to dry out before I can begin pouring cement in them.
A slight change of plan is to use a loop of garden wire through the liner to fix both halves of the casting tight together.
You might just see a loop of green wire where the next mold goes.

Last edited: Thu Feb 22, 2007 11:34 am

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Gardenstew wrote on Thu Feb 22, 2007 9:56 am:

Very clever logical thinking Pete. I can see the finished effect in my head as you described it so well. It should almost look like a single row of cobbling.

I agree with you about February, dull, dull, dull.

Gardenstew wrote on Thu Feb 22, 2007 11:37 am:

Aah thanks for adding the pic Pete. Almost as I imagined except a little bit taller. That will look great!

eileen wrote on Thu Feb 22, 2007 11:54 am:

Now that's what a call a really neat idea Pete!! You must let us see the pond when the blocks are in place. If they look half as good as I imagine then they'll be the perfect way to cover up that pond liner.

zuzu's petals wrote on Thu Feb 22, 2007 12:25 pm:

Fiendishly clever!! ;-)
Will you use a release agent inside the bottle/molds?

devonpete wrote on Thu Feb 22, 2007 1:51 pm:

The blocks won't be a tall as the plastic molds as I want a flush to the path look. I also have to mow grass further along and anything sticking up will be a problem.
No release agent...I'm just going to cut the bottles away. They're cheap enough (zero cost! - see my tagline 'The best things in life are free...') to discard and use once only.

pondlady wrote on Thu Feb 22, 2007 1:58 pm:

Be careful, Pete. Concrete leaches lime and can cause the pH of your pond to skyrocket and kill fish and plant material. I might either rethink the in situ idea, cast them elsewhere, clean with a muriatic acid solution or paint them. You can also let them age somewhere away from the pond for at least 6 months and then they should be OK.

devonpete wrote on Thu Feb 22, 2007 8:21 pm:

This is obviously sound advice based upon known fact, although personally I've not had any problems so far with other ponds I've worked on which have had close contact with cement work. But I shall of course bear it in mind.