A Garden Pond

This is a page about a journey into unknown skills. This is the story of a garden pond.

In 1998 we bought our house and two years later rebuilt the back garden by lowering one end and raising the other. This created a reasonably steep end and as it had solid rock underneath it I decided that it might be a good place for a stone seat. Eight years later and the number of people who actually sat on it I could count on the fingers of one hand. And so an idea dismissed when our children were much younger now came back. A garden pond.

What's the choice?

Well Prague has come a long way in the last 10 years regarding consumer goods but the main offer was still PVC for the base or a moulded fixed shape. I didn't want to just dig a hole in the ground but, we did not have the space for a huge shallow pond either so the idea of an ornamental pond made sense. I figured that I could build a pond that was part underground and part above ground with that part being decorative in some way but, there were few examples of this kind of pond either in books or on the internet so I started to write down my ideas and scrawl a few drawings.

The beginning.

Well here's the starting picture. The old stone seat that nobody ever sat on. I knew that I wanted to use the stones in some way and started adding to them by raiding other parts of the garden and acquiring rocks from our village etc.

Pick and shovel.

For the next 6 weeks I could be seen with either a pick or a shovel in my hands pulling out stones or rocks and generally moving earth and stones around the garden.

The first hole.

Here you see the first hole which was planned to be the deepest part of the pond at around one metre. The pond dimensions naturally settled on 3 metres by 2 metres after the sides were dug out. I was trying to imagine where exactly the level of the front of the pond would be if I took the back of the ground as the top level (hence the stick) but I soon realised that before I went any further I would have to know the size and type of the blocks that I would be using. It was time to visit the builder's merchants to get some prices etc.

The foundation.

Having determined that I would be using a hollow concrete block 50x20x25 it was a simple matter of picking the spot at the back of the pond that would be level(ish) with the front when two levels of blocks were laid. These were strictly "wall" blocks of the interlocking type but as I had three right-angles and a curve they wouldn't be interlocking for long and not at all on the corners. Then it was measuring for the footings to allow for the block and rocks in front of it. I dug about 30cm footings on three sides and thought I would leave the back as it was earth. My neighbour who has just finished building his house took a quick look and informed me that maybe the footings were not deep enough.

The foundation continues.

This was becoming too much like hard work. Digging, digging. The footings were now increased to 70cm on the front side and 40cm on the other sides as I hit rock any deeper than that. It was back to the builder's merchants to buy the blocks, steel, sand and cement. This entailed asking for the right type of sand and then based on that amount it should be easy enough to calculate the cement required (but it didn't quite work out like that). The main steel was planned to be 10mm and bent into a U shape to bind the blocks vertically. Secondary steel was 7mm and left in lengths to provide horizontal support. Additionally the corners had upside down U shapes to bind them (one block was broken as I was learning to chip a hole in the block). By the time we left the builders merchants we'd ordered two tons of sand, 200Kg of cement, 32 concrete blocks, 36 metres of 10mm steel and two 7mm reinforcing sheets. The picture shows the footings now completely surrounding the area and the 10mm steel bent to shape and positioned over hardcore.

The wall begins.

Fortunately my neighbour loaned me the use of his cement mixer and helped me mix the foundation. It took four hours, used 300Kg of cement (had to buy more) and just short of one ton of the sand. I also lost about 1Kg in weight and ended up hauling more than one and a half tons of materials across the lawn. This was left for three days before the first layer of blocks was put on. The far right corner was planned as the run-off point so this had no blocks. Instead I used a normal concrete mix for the bottom half and eventually would finish this off later so that this point was slightly lower than the rest of the pond.

The wall continues.

The second level of blocks was positioned and this time I was on my own to do the mixing and carrying. This again accounted for just over half a ton of sand and another 8 bags of cement (200Kg). As the blocks did not interlock on the corners I was left with a few gaps which were filled and left to dry for a couple of days. At this point the three main retaining walls were complete and the last corner (run-off area) had to be prepared. For this I used my 60cm spirit level and part of an old bannister for my extension level measuring. I worked around the pond to find the highest and lowest levels (the difference was about 3cm). I added extra concrete to the top of the wall at the lowest point and set the level of the run-off at 2-3cm below the pond water height.

The wall continues.

Up until now it had been all digging, shovelling and grey blocks etc. Now it started to get a bit more interesting with the decorative side of the pond which would also provide strength to the structure but, look nice. We'd collected and scavanged enough types and sizes of rocks to make an interesting wall but, I can tell you that positioning rocks weighing 25-50Kg is not for the feint-hearted. It's back breaking work but, after nearly seven hours I had about 90% of it done. Inside the pond received more sand to lessen the angle of the corners of the walls.

The liner and electrics.

Taking advice from a local pond company I elected to use regular underfloor insulation as the base protection even after removing all possible sharp objects. I used two layers (approx 30 square metres). It was a bit fiddly to start with but as you add weight it kind of finds it's own fit but, don't do this on a windy day as it will blow everywhere. When running power for a pond you should use a direct feed from the circuit breaker board but, I didn't have this option so I extended a normal ring main underground and added a 10W low-power pump.

The liner.

This was the single most expensive part of the project as you'll find later in the pricing. Without exception, every book I read and every webpage I surfed said rubber was more expensive but, use it if you can afford it. It had qualities making it easier than PVC to handle, less likely to be punctured and more durable against the sun. The sheet was a single layer measuring 6m by 5m and it took two people to lift and position it. The only technical bit here was to mark the centre of the sheet so that I could see where to position it in the base of the pond.


By now the inner retaining wall had had two weeks drying and the outer decorative wall one week so I felt safe to start filling the pond to the first level i.e. 20cm above ground. This was left for a further week and then filled halfway up the upper block. This was crunch time as we kept filling to the level of the run-off point. I'd spent nearly a day on the levels but, still it was a nervy time seeing the water rising until finally I could see the excess running off and 2cm to spare on the next lowest level. This was left for two days to allow for the weight of the water to pull in the rubber sheet as required. At this point I added a piece of the steel reinforcing to provide an extra bit of security so that nobody could fall into the deepest part and to provide a place for larger plants to stand. The rubber lining was then trimmed to make it more manageable as it was difficult to deal with large folds.


I bought the capstones from a local rock company as I needed about 5 square metres of approximately the same width and size. I bought what in Czech it's called Andezit (mix of granite and iron-ore) as I'd used larger pices of the same kind of rock in the wall. The pieces ranged between 1 and 3 cm thick making them quite strong but, easier to work with. This was the third biggest expenditure. Once started it took about two hours to work my way around. The run-off area was left loose as this will be extended to the right. Everything else was set in concrete. The waterfall area is free standing using the rock weight for stability and the wooden half-pipe (found on a walk in the woods) served as the water-drop. I use a 10W pump with one metre half-inch pipe rising 60cm from the pump which delivers 480L per hour. This is perfectly ok for a pond our size.

The change.

Just to remind you of what it looked like before.


The waterfall is working. We have just started to add lillies and oxygenating plants and we've already got our first frogs. Very pleasant to be in the vicinity of the pond (have to stop myself saying pool). I wouldn't recommend this for everybody but, for me it was a learning experience and I'm physically fitter as well after shifting 5 tons of materials around.

Materials and Costs

br> Tools:
Pick axe
Spirit level
Cement mixer
Angle grinder
Wire brush
Metal File

Labour: Free
Tools: Trowel 45kc
Loaned equipment: Cement mixer, angle grinder. Free.
Original order: Sand, blocks, steel, cement. 7000Kc.
Additional cement: 14 bags. 1200Kc
Rocks for wall: Free.
Electrics: Extension 2x socket, 17 metres cable, plug, underground protection. 680kc
Liner protection: 200Kc.
Rubber Liner: 9000Kc
Pump: 500Kc
Capstones: 5 square metres. 1750Kc

Duration: 10 weeks.
TOTAL @20000Kc, 635 pounds or 760 Euros.