At least I've not seen a DIY of this kind of koi pond build... Pond Description
This pond is approximately 10' long, and 5' wide, supporting a 2' depth of
water. This is build with 2x lumber and a pond liner. The filtration I have is
centered around bog filters, with a mechanical filter prior to each.
The key characteristic of this pond is that it is it is fairly easy to
dismantle and re-assemble in a new location.
It is small for a koi pond for full grown koi, but bigger than what I had previously. I expect it would
make a good grow out pond, or gold fish pond.
Why this pond
Where I live, the laws require a pond more than 2' deep to be permitted, part
of being granted a permit is having a 6' high fence. Also I live in a strata
community, I believe called a Home Owners Association in the US. The Strata
owns the fence, and does no allow changing it (or building one right next to
it). As such my pond is limited to 2' deep.
Being only 2' deep allows me to use the building technique I did. And that
technique allows me to easily disassembled and re-assemble the pond. This is
important as where I live it gets cold enough to freeze this pond solid.
This building technique is relatively inexpensive. Although, with the cost of
wood these days, not exactly cheap. I'd guess the material cost for the pond
is around $600 Canadian (2024):
Product cost qty
8' 2x6 $6.50 22 (Spruce)
8' 2x4 $3.75 13
paint $50 1
liner $250 1 (cheap HDPE, and enough for two)
Insulation $25 4 (styrofoam with plastic sheath on sides)
Please keep in mind I was not actually really keeping track of costs, but that should
be close. I had most of my wood on hand, including cedar for the top rail, and
carpet for the bottom . The estimate assumed spruce/pine throughout.
Estimate excludes: filter(~$200), and tools (Skill saw, Miter saw, chisel, and drill).
Note that you can buy a similar pond. In North America do a search for Kim's
Ponds, and in the EU/UK "Norlog" ponds.
Also this is the first pond I've built, these instructions are provided As is, in the hopes it helps someone. In short use these instructions and the resulting product at your own risk.
The Model
I did have some concerns about this build method, specifically for strength.
So I built a model from some wood scraps I had lying around. The scale is around 1:5
to the real pond I build later. It turned out well enough, I've been using it
as a hospital tank, a tank I grew out some guppy fry, and right now it just
has a few peace lilies growing out of the water. It has been in use for over
a year.
It was built with a very sloppy method. all cuts made by hand.
yes there is a leak in my model, covered that with tuck tape worked fine....
A few lessons learnt from it:
1) Reinforced the need to avoid the sloppy / inaccurate cuts.
2) At the scale it held up well with some bowing but no breakage. Note that the
scale is such that the depth is about 1:5, but the wall thickness about 1:6,
with larger panels. So the stress on the joints should be proportionately
higher, than the real pond.
3) A current in the water (or waves) into a fold in the corner can climb up pretty high as the fold
constricts the wave, and out over the rim if there is not enough free board (height from water level to the top of the pond liner.). If you are filling close to the top of the liner, tape on the folds may be warranted.
I concluded from using the model I could build a viable pond with this method.
Making accurate cuts: - Angles and Spacing
This style of pond requires accurate cuts, specifically accurate placement of
the cuts, and distance between them. The Key is the distance between notches in each board be the same.
I made each notch about 1/16th of an inch wider than the 1=1/2" should have been needed for a nominally sized 2x lumber.
1/8th of an inch may be more appropriate. I found after breaking the pond down,
letting it sit outside much of the winter, and then painting it, that I could
get it to go back together but it took some force. I did end up making a
couple notches a bit wider to allow re-assembly. Also taking it apart to move it later I'd broken a few of the flanges/shoulders between the lap cut and the end of the board off. Gluing and screwing these back on has held so far. Anyways I assume you are going to use 1/8ths of an inch extra, and the instructions below reflect that.
How to get accurate material, and accurate cut:
0) Start with wood that is straight, not cupped, and not twisted. Additionally, when selecting the wood also get wood that does not have large knots in it, smaller and fewer the better. Also ensure the ends are not split.
After you cut the wood and lap joints, paint it or otherwise sealing it from moisture
ingress/egress, which will reduce future crowning, twisting and bowing of the wood.
1) Ensure all boards were the same length. I used a miter saw, and I
re-trued it to square as best I could before cutting the boards.
Each board had both ends cut, the first side has only a few mm cut off just to square it up, then second
to set the length to be the same on all boards. You are aiming for as close as possible, within 1/32 should be achievable with a miter saw, and a sharp pencil. Ensure the board is sitting flush on the cutting base, and tight to the fence, and the saw is coming down perpendicular in all 3 dimensions. Take this opportunity to verify no splits in the end of the board.
With all boards the same length you can now use a jig that only fits on one end, to get all the cuts for the lap joint in a consistent location.
2) I made a jig to cut out each notch, for use with a skill saw. (note my
boards were originally 2x8's that were ripped down to 7" for another project,
which I took apart. If I had 2x6's (which I'd recommend) I probably could
have cut the notches with my miter saw and a depth stop, but at 7" I could not quite get the
depth I needed.
Note in the picture above the, the back piece I mention below is not yet installed.
Building the Jig:
The Jig I made was pretty simple. It was two lengths of 1/2 Plywood about 2.5" wide and maybe 20+" long, these act as rails which slide down over the edge of the board to be cut. It can't be wider then the material you are cutting. For example if you are using 2x6's and 2x3s, then it cant be more than 2.5 inches wide (the width of a 2x3).
An end cap is screwed into one end, and a diagonal (45 degrees for an octagonal shape) top piece used as the saw guide. The back side has another cross piece over the top of the two rails.
I used 1/2 inch ply wood as it is what had to hand, consider going with something a bit beefier. if using plywood I recommend pre-drilling the holes, to avoid splitting the wood.
I set the diagonal piece is set back from the end 7 inches, at the short side.
So that after the 1-1/2+ notch is cut there remains about 4" of a flange/shoulder of board
after the notch to the end of the board. The other edge will be about 5.5 inches.
When building the jig you want a little bit of extra width, so it slides onto the board to be cut, allowing for some variance in the thickness of the boards. To achieve this I used some strips of card board from a serial box. the rails are clamped onto a piece of wood of the same thickness as the boards you will be cutting. The serial box strip is between one rail and that wood, acting as as spacer. Clamp the rails so they are flush with both the top and the end of the wood. Then screw the end piece across the front edge of the rails. Screw a the top piece across the top of the back. You'll be hitting this top piece to slide the jig forward, so it should be well attached, and fairly robust. remember, if you are using 1/2 ply wood pre-drill the holes so it does not split.
Clamp the partially build jig on the 2x4, so the top edge of the jig aligns
with the top of the 2x4. Mark a 45 degree line across the top of the Jig, starting 7 inches back from the end, and angled back from the end (so the line other side of the jig is about 8.5 inches from the end). This works as a skill saw will have a 1.5 inch gap between the edge of it's guide, and the edge of the resulting cut. The guide strip should be wide enough to get two screws in it down into the edge of each rail. and
long enough to use as a guide for your skill saw. (say 12-16").
If you want a square pond, then install the saw guide at 90 degrees.
A note on the theoretical shear strength of the flange/shoulder. After making a 1-5/8 notch cut, the above measurements leave the shoulder with the short side being 4-1/2 inches (and 5.5 inches on the longer edge). The area of the shoulder corresponds to the shear strength it has. According to https://extension.okstate.edu/fact-s...lications.html (in turn referencing wood work handbook 1999), white pine has a shear strength of 900 PSI. At 1-1/2 inches thick that means leaving our ~ 4-1/2 inch shoulder should have a shear strength of about 6000 pounds. (hmm, do you trust that number I'm not sure I do. Note this does not mean it wont split if there is a wedge there, so make sure you cuts are clean). In my pond the water is 2' deep. At 3' water pressure is about 1.4 PSI. using this number for some safety margin, a 7' long 2x6 board at 2' deep will have < 1.4PSI x 5.5in x 7ft x 12in/ft = 600 pounds pushing on that shoulder (and only 1/2 that since it is shared between the two ends). So in theory we have better than a 10x safety margin, if I did that math right and understood the usage of the formula for this application. I'm not sure I did, that is why I built the scale model.
Using the Jig
Anyways, the Jig is used to cut the notches kitty corner on on all boards. Once that is
done the diagonal piece is reversed, being sure it is set to the same depth, and the other pair of kitty corners is cut on each board. Only cut one edge of the top and bottom pieces.
the picture above shows the Jig in use, just before making my final cut. I've tapped it forward already and made the cuts seen.
Making the cuts
- Set your skill saw to the correct depth (1/4 the depth of your board - 1/2 the gap between boards you want)
- placing the Jig, tap it into place so it is snugly set at the end of the board.
- clamp the Jig (not done in video, I started doing it afterwards, as it would shift during the cut.)
- Incremental cuts (tap the jig forward about 1/4 to 3/8s of an inch, and run a second cut. Stop when the edge of the guide strip gets to the edge of the first cut. This will give you a notch = 1-1/2" + the thickness of the saw blade (typically 1/8 of an inch).
- Chisel out material in the cuts
- do the two kitty corners on the board
- After done for all boards, remove the guide bar, and re-install it in the other direction. It is important to get this as close as possible to the same distance as it was originally installed.
- Then repeat the above for all the other two (kitty corner) remaining cuts to be made on each board.
All notches should be angled inward to the same edge of the board
I'd recommend the depth of the cut be such that you end up with about 1/4 of a
gap between boards to allow for crowning. So if using 2x6 and 2x3 stock I
think this works out to a 1-1/4" deep notch. Notice that I messed up this on my build, and got a thicker gap than I wanted. The cut on the 1/2 wide board cut may need to be cut a bit deeper so the top and bottom edges end up flush. How much depends on the wood you use. A 2x3 is less than 1/2 the depth of a 2x6, it may be easiest to cut the wider boards first, then simply line the two boards up side by side to gauge the depth. - This is something I missed doing, and have not fixed as of yet.
In all seriousness, be careful. I don't recommend going out and buying a skill saw and do this as your first project with it. It may be called a Skill saw, but you have to bring your own the skill. if you do, this is one tool where you really need to read the safety instructions in the manual. I've long since lost mine, or I'd scan it and include it here. As a minimum:
- Do NOT allow the saw to twist as you are making the cut. That is ensure you can make a strait cut all the way through,so the saw does not bind and kick back.
- Do NOT stand directly behind you cut line, or let anyone else do so. (in case you fail at bullet 1, and there is kick back)
- Do make sure you have a solid stable stance, and can firmly hold the saw all the way through the cut.
- Do NOT get bored and stop paying attention to the above.
- Do wear hearing, eye, and breathing protection.
- Do clamp your board in place, and your Jig on the board, so nothing moves unexpectedly. With that you can hold the saw with both hands.
I'm not an expert, the above is given with the best of intentions, but may not be the best advice, and may be incomplete. If you use this method you do so at your own risk. If you don't have experience with this tool, maybe use a hand saw, or get someone who does have the experience to make the cuts for you.
building the top rim, and seats/ledges
I built my top pieces out of 2x cedar, as I had some nice boards available (I
was going to build a cedar strip kayak with them)
I cut the top cap piece to length. Because my over all pond is 8 sided
octagonal shape, the boards ends are cut with a 22.5 degree angle.
The corner seats
A Two boards are laid out side by side, cut to length so that they extend over the sides walls of the pond by enough so that they end up flush with the outer edge of the side tops discussed in the next section.
I ripped some scrap bits of a 1x4 cedar in half (you can just buy 2x2 pieces and use those), with a length of 10 inches or so. These are screwed from the bottom up with 2-1/2" screws to hold the two boards together. They are located so that they will sit on the outside edge of the pond side wall. A third is also screwed from the bottom side, but this one located so that it will sit on the inside edge of the pond parallel to the seat itself. These act as cleats to lock the seat in position so it can not slide in any direction. Also, importantly the inside one has the liner tucked between it and the pond side wall to pinch it in place so it does not fall back down into the pond. A bit hard to describe, hopefully the video or pictures are clear.
The side tops:
These consist of a 2x6 cedar board, with similar cleats on the under side to hold the rail in place. The outside cleat runs the full length of the board. The inside cleats are smaller lengths, installed every 2 ft or so.
These are centered are screwed up from the bottom length wise to the 2x6. They are placed such that a gap is present allowing the top to slide down on to the side of the pond. This was done by placing a temporary 2x4 spacer + a ~3/16 inch spacer (a few layers of that serial box cardboard). Note the liner I use is disturbingly thin, if you use thicker EPDM, then you will need to space these out a bit further.
The resulting piece then slide down onto the edge of the top edge of the koi pond.
board of the pond, giving it a nice looking cap. very importantly it too also hold the liner up as it is
tucked under the top piece.
Painting the pond
Do paint or otherwise seal the wood on all faces including the ends. This help reduce cupping, twisting and splitting of the wood by reducing changes in moisture content.
Putting the pond together
The pieces just stack on top of each other. (the 2x3's go down first on alternating sides across from each other). They the boards should easily slide into each other.
bottom liner protection
You probably want some bottom liner protection. What you use depends on what the pond, and hence liner is sitting on. For me it is a brick patio. I used some carpet off cuts cut to the shape of the pond. You want something under the liner so the pressure of the water (or someone/something walking in the pond) does not push down on something sharp and puncture the liner.
Side Liner protection and insulation
I have large daily temperature swings where I live. so I choose to cut rigid insulation to fit the inside of the pond. The trick here is to cut at the 22.5 degree angle, and to the correct length, so that the insulation pieces hold each other in place. This insulation also protects the liner from any slivers or sharp bits on the wooden walls. I'd advise some kind of protection on the sides. If you don't use this, make sure the wood is sanded smooth prior to painting it earlier.
The Liner
Type selection
I used HDPE, mostly as it was available a the time, in fact I got the very last package of it at teh store I was at.It is not unreasonable in terms of looks, if you have a pond with a flat bottom and straight sides, as is the case on this pond. It is also very light, but not super easy to fold in the cold. The fundamental question is, is it strong and hence safe enough to use. As mentioned I bought the last package at the store, it was folded and had a harsh crease in it, on at least one corner. I did seem to have a pin hole leak (I never found the exact hole). I ended up running Gorilla 'flex tape' across the center fold, which included that point. that seems to have stopped the leak.
I believe most pond folks would recommend EPDM (rubber like) liner.
Installation of the Liner
The Installation of the liner consists of Trying to get it to lay flat on the bottom. putting in an inch or so of (warm) water helps with that. Then folding it up the sides in a reasonably neat way. This sounds really easy doesn't it. I did find I ended up walking in the pond, to ensure the liner went all the way down into the corners, making that under the liner protection important. From what I remember:
Folding the corners so that you have the angle part of the fold behind the visibile fold looks better to me. That way the visible fold runs strait up the vertical corners.
The folds become disturbingly tight when water is in the pond, no leaks so far, at least as far as I can tell.
Once to the top of the pond wall I folded the liner back down into the pond on the corners (the short wall sections with the filters on top).
It is critical, that none of the liner material behind the folds slopes downward below the water line. An obvious statement, but I'm not sure it is always obvious when it occurs, so pay attention to that.
Once I goth the liner to where I liked it I cut off the excess edges so that they will fold under the top cap, allowing the top cap to hold them in place. The corners only go up to the top edge of the wall, and fold back down, but are held in place by the cleats on the seat. I think next time I move the pond I'll be at least taping the liner in place, or some how a fixing them a bit better.
My liner is now cut to size, the length ways as actually very tight out of the package. when moving the pond I have to be very careful to get the liner centered. prior to adding the water. Clamps are your friend when doing this.
Introducing the The Filters
I'm using bog filters, with mechanical filtration around the pumps feeding into the bogs. I'll do a separate video on building these. For now I recommend the youtube channels "Ozponds", "plantedlife project" and "Rob Bob's Aquaponics"
The big difference from planter based bogs I see online, is I run the output back down out the bottom. to reduce noise (which My wife dislikes), and evaporation. and I think it looks cleaner.
I do want to clean up the look of the input filters, and tubing/piping in the pond.
Recommended changes
- wood size. After about 8 months, the 2x material on the long side of the pond is bowing out a fair bit, more than I like. It deflects out about an inch. So if going 2' deep I'd recommend thicker wood board, or doubling (or tripling) up the boards. If you do triple them after cutting the lap notch across all three boards, then consider raising the center piece up 1/2 an inch to get a tongue and grove action between layers..
- cut size. I"m not sure on this one, but I think I'd made my notch too tight a fit. I'd tried to allow about 1/6th of an inch, I'd increase that to 1/8th of an inch, which is easily done as it is the width of the circular saw. So when sliding the jig, for the final cut, stop when it is flush with the first cut.
- Maybe use a quality EPDM liner. HDPE is working for me so far, and it is probably good enough as it does not need to stretch around curves and the like. However the internet says EPDM is generally considered a more reliable material. I only have experience with the HDPE liner, on this one pond. It is light and inexpensive.
Sorry not sure why some of the pictures are upside down, nor why that final picture is at the bottom.
Very nice! Lots of construction detail provided. There are a lot of cuts and intersecting pieces that may need numbering when dismantled?
I made a simpler liner pond out of treated pine rectangular sleepers because we often have termites near moisture.
The sleepers are 200mm (8 inches) wide and up to 3600mm lengths (12 foot) and come in 50mm (2 inch) or 75mm (3 inch) thickness.
Held with 2 baton screws on each corner of each layer which are easily removed. I have dismantled and transported it three times now.
Then topped with a thin plank to stop turtles climbing out which is convenient for sitting on or resting cups of coffee.
The one in photos below is 8 foot long x 4 foot wide x 2 foot deep used for my two turtles (no koi) so there is heat and UV lamp at one end.
As it was only 8 foot long, I used 2 inch thick wood which cost approx US$10 per length in Australia.
It would be very easy to make a 12 foot x 12 foot x 2 foot or higher high version.
Filtration was a 5 gallon bucket of 6mm gravel with a small water pump buried.
It's easy to lift out the entire bucket to rinse clean. I grow a water plant in the bucket to hide things
Thanks Aquaholic,
I like your pond as well. One difference when I say I used 2x material (say a 2x6), that is the pre-dressed size (supposedly) so once they are planed smooth before being sold, they are actually only 1.5 inches thick. So my pond walls are not actually 2" thick.
A question on your pond: How are the wall layers affixed to each other, or is it just good old gravity and equal water pressure on opposing sides holding them in place?
To answer your question. No need for numbering of my boards, at least in theory, as there are only 3 lengths of boards for the walls. The top and bottom edges of the walls only have cuts on one side, so it is pretty clear which ones go where, and when. Having said that, I've moved the pond 4 times now, and I did find that I had some trouble putting some boards in some locations, so numbering them may have helped. That is part of the reason I recommend allowing for a total of an extra 1/8th of an inch on the notch widths, for someone that may be interested in building this style of pond.
The top seats/plant ledges need to be in specific corners, due to the filters I have sitting on top, and the way I have the plumbing run to/from them. Now that you remind me, hopefully I'll remember to label them next time I take them off.
I agree your pond would be easier, and if the rings/layers just sit on top of each other then faster to take apart and put back together too.
Hello Myrl,
Yes the layers just sit on top of each other unfastened. The water pressure at 60cm depth is negligible. I used two galvanised countersink batten screws in each corner but one screw would probably suffice however they aren't expensive. With a cordless screwdriver its very fast to undo.
When I moved the pond, I didn't unscrew the corners, just moved as three separate rectangular frames as they aren't that heavy.
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