Pond help

[kellys_eye]

This weekend we had the earthmover in and flattened the garden - it was a 'hump' that took up most of the usable space (with a decking platform on top) and we've now got a much larger and usable flat area.

One thing we did lose though was the original pond - no big deal as the fish ended up as food for the local otter - but Mrs k_e loved her pond and I want to make something suitable to replace it.

The banking that we have (in places) seems ideal for 'insetting' a half-octagon shaped pond like the picture shown below.

What I'd like to know is if the post arrangement (set in concrete) plus planking (47mm C16 treated) will be sufficient to hold back the water. My 'instinct' tells me it will be fine as I generally have a good concept of loads etc but this is one construction I don't want the missus getting wet feet over.

Any pond-makers out there with advice on my design?

[Someone-Else]

There isn't that much load to worry about, as the majority of the weight will be supported by the ground under it, not to one side. The one thing I would ask is what are you planning on putting inside your half hex? I will guess liner?

[kellys_eye]

Yes, quality pond liner, stepped up the sloped banking.

[Someone-Else]

It wasn't the soil side I was "worried" about.

From your drawing (correct me if I am wrong) You are going to put wooden posts into concrete then "layer" (for want of a better word) "slats" (supported by the wooden posts) from the ground up, then fix a "lid / shelf / narrow seat" on top. Then put the liner in and this last bit will cover the top edge of the liner.

[kellys_eye]

Yup

[Someone-Else]

Thought so.

It sounds good, but in practice it isn't.

If you do it exactly as said when you put the liner in and fill with water it will "hug" (Actually its forced) the inside of the "slats" not only will it show every small gap / imperfection, it will also "hug" the support pillars showing a bulge and and also the high potential for the liner to fail on the support pillar edges.
Then after a few years when the fixings or the hole for the fixings for any of the slats fail you will "whip off the slat and put a new one in" As soon as you do the liner will bulge through this new gap and if it doesn't then puncture you will find you can't get it back in the pond. I know it came out, so there for it must go back in, but trust me it wont.

Alternative 1

Put "slats" on the inside of the pond before the liner goes in. This way the water is pushing the slats towards the support pillars, not as it was before pushing the slats out. The only problem is the timber will rot and will need to be replaced. Not so bad now, but when you get older, you will wish you had done alternative 2.


Alternative 2

As you are going to dig holes for the supports, dig a trench and build a small brick wall.
The advantages are that it will never need replacing, it will not show any indentation / marks on the liner. You can then use your choice of material for the top.

[kellys_eye]

The 'slats' are actually 245mm x 47mm C16 (only two, one on top of each other to give a total finished height of 500mm above ground) which will be 'dowelled' together along the joining surfaces. These 'slats' will be bolted to the cemented-in uprights. I don't expect to see any protrusions on the inside (recessed nuts/washers) other than the supporting posts themselves. Rounding the edges of the uprights and providing ample 'loose' liner material should prevent any stress failures of the liner itself (?).

With only a maximum span between uprights of 1.8m I can't see any undue stress levels occuring. Worst case I will change the 'posts' to upright lengths of C16.

The 'open' back end is to be layered onto the sloping ground which is 'stepped' (similar to the stepped slat ends you can see in the drawing) to allow for placement of water plants etc.

By this method the only water touching any woodwork whatsoever are the posts in the ground (cement) and the lowest edge of the bottom 'slat' - all of which would be appropriately treated before contact. All/any holes, bolt recesses etc would be mastic'd flush.

If I have to service the pond to any great extent i.e. replacing a slat, I would empty the pond as required.

I appreciate your input though.

What I want to completely avoid is brickwork..... as good as it may be it's more work than I think is necessary. The only uncertainty I had was the weight of water (pressure) against the wood itself. My spidey-sense told me it would be ok but there's no harm in taking a second opinion (thanks for that too).

[Someone-Else]

No worries, my pleasure and of course Take some as you go.

[mikew1972]

1/2 your depth along the 'wall' is 250mm. At 0.25m depth water pushes with a pressure of 0.365 Psi in all directions.
That's about 96Lbs of push on each M of wall if I got the maths correct.
Is doing it in brickwork then cladding it out of the question?
The load at this depth isn't great but wooden posts and fencing have a limited lifespan especially when you can only paint one side with a pond friendly preservative once installed.
At least use concrete posts?

[kellys_eye]

Thanks for the maths Mike! Brickwork is always possible but is something I deliberately wish to avoid - mainly because I have the timber as 'scrap'.... The figures you quote seem well within the capabilities of a timber post/backboarding solution though.

The timber, as well as being preserved, won't ever come into contact with pond water due to the liner being used and 'fencing' is a bit dismissive of the quality of the wood being used. Also, given its relative simplicity I figure that maintenance or parts replacement (boards etc) would be a once-in-10-year event (if that).

One change I may make is to put the support posts outside the tanked area to keep the inner wall flat as per someone else's suggestion above.

[kellys_eye]

Wow, was it that long ago.....

Anyhoo... update time.

The pond project changed tack somewhat ("Oh noes" I hear you cry) and ended up being a 50th birthday prezzie for Mrs k_e (her suggestion).

We had a patch of ground that was headed towards being a rock garden - it was actually the place where we burned 90% of the original house during the rebuild process so was pretty crappy and potentially toxic hence piling rocks on top of a groundsheet. We had placed a small (2m x 1m) pond in it just for the heck of it but whilst sat watching the fish we felt guilty at the meagreness of it so plans widened somewhat.

The patch of ground slopes some 1.2 metres top to bottom and extends about 6m x 4m in total size - has a cut down stump of an old beech tree at one end and is pretty irregular in size. Anyway I had to fit four posts to bring one sided of the pond up to the top level and used treated logs (10-inches diameter) set 1m into postcrete.

Across the posts I bolted 10x2 boards and also built up the sloping edges in a similar fashion using the beech tree as a pivot point. This eventually gave us a 'pond of weird shape but the finished look is quite appealing. We then dug out the lowest parts to a depth that when filled with water gave a deep section of at least 1m across the longest wall, sloping up (with a central deeper pit) to the shallow end that is only 6" deep.

The idea was to give us water cover that could support many different forms of fish and amphibians. After fitting the appropriate liner we took four days to fill it!!! The top edge of the pond was covered with some old boards left from dismantling old decking. Looks a bit tatty but when funds allow we'll be changing this for something a bit more in keeping with the layout.

We now have dozens of fry from three of four of the fish species we bought, toads, newts, snails, sticklebacks and assorted breeds of fish (standard goldfish, ghost carp, shebunkin(?), orf, golden tench, serisa comet (?) - can't guarantee the spelling )

The cat (one of them) had one of the biggest fish - an 8-inch comet before we taught them that they were 'pets' and not 'food'. Another of the cats had swimming lessons - involuntarily of course but they've now settled down to just watching them with us. The local Heron has been kept at bay by a fake Heron and other pottery-type birds on various tree stumps around the place.

Even after just 2 months the pond is very well established - moss and other fresh water plants gathered from around the local area has made a huge difference too - and we spend an hour each day just sat beside it watching the antics of the fish!!! It's incredibly therapeutic as well as relaxing. Once we have a decent layer of sh1t across the bottom of the pond we'll be scattering some decorative gravel around to lighten it up a little. Otherwise it's one of the most enjoyable projects we've undertaken.

Couple of low quality pics attached ( one with the liner fitted and part filled at the 'deep end' and one after completely filled) but I'll try to find the hi-res versions later.

[Someone-Else]

Different.

But I am sorry to say, I don't like the "tree parts" but not for the reasons you may think.
It really does depend on the type of tree but in short anything dead and organic will rot, as it does so (all be it slow) it will use oxygen and give out decaying matter as it rots. Your pond ecosystem may be able to cope for a while, but eventually it will not be able to cope. (Its why you don't see them in other ponds) Live and growing, not a problem. (Well, the leaves can be) and you can get "specialised" wood for use in fish tanks.

Fake herons are often used to deter other herons...............so people think and the folk who make them want you to believe. Herons are not "territorial" and if they see another heron, it is assumed there must be a good food source, so come down to see what they can have.

[kellys_eye]

The (large) tree is not actually in the pond, just used as support for some of the boarding, but there is a smaller stump set in concrete that was part of the rock garden originally. That 'stump' is still growing despite being set in concrete and has sprouted some very attractive offshoots, leaves etc. Same goes for a large branch placed across the pond - each end is in the water plus an intermediate 'elbow' but again the branch is growing (sprouting) so not really dead/decaying in either example.

The pics are at least two months old - the pond has matured considerably since then - much more greenery, lilies, grasses, moss etc etc. I'll get some updated pics shortly.

Yes, the stump and branch may die off and properly rot but they will be removed well before/if that happens.

Can't comment too much on the Heron issue - I've watched a Heron land and then leave the area. Whether this has anything to do with the fake Heron is arguable but it was a small expense with potential usefulness. Anyway, our cats will probably be more useful for that particular problem!

[wine~o]

Kellys... are you sure that pond is deep enough for the fish to survive Winter ??

Mine is about 3 foot deep and even in a harsh winter "darn sarf" it's only just sufficient.. where you are you might need 4 or even 5 feet of water...

and when did you last go skating on a Loch ???

(Typical stereotypical "I'm a southerner" stuff ....)

[kellys_eye]

Lots of misunderstood thoughts about Scotland and 'cold' temperatures wine~o....

Whilst parts of Scotland certainly can get REALLY cold, the west coast is generally very mild (gulf stream warming etc) and wet which is why some places have palm trees and even we had a giant yucca plant (tree) in the garden when we first moved here.

Of course there are occasions when the old pond used to freeze over and even this one might be susceptible in the harshest of weather but we'll fling a big heater in there for the few days that such cold snaps occasionally last. I'd be more concerned for the ice cutting off the oxygen than the actual cold - I doubt the pond will freeze 'solid' - but we'll have to see how it goes