When I was about twelve years old, I decided I was going to create a pond in the back garden. Having never undertaken anything like this before, I was blissfully ignorant of any technicalities or possible problems that might be encountered.

I just dug a pear-shaped hole in the ground and with the help of my cousin, mixed up a quantity of cement and sand (which handily came from the excavation). I think we had roughly the correct ratio and simply slapped it onto the sides and base by hand, let it dry and there it was.

And there it stayed, for many years as a matter of fact and this was somewhat miraculous because this concrete liner had absolutely no form of re-enforcement, no water-proofing agent and no leaks! Over the years, I made a few improvements such as a rockery into which I eventually incorporated a circulating water cascade (that was a learning curve) and I doubled the size of the pond itself.

The point is that from an early age I was hooked. From just a hole in the ground to a well established and attractive water feature, which was admired by many, I had founded my reputation as a pond builder and was sought out by many who wanted a water-garden on their plot, as the man for the job.

Although I continued using the concrete method for years after and having mastered the proper re-enforcing techniques, it was only a matter of time before I was obliged to employ the use of Butyl rubber.

My first encounter with Butyl rubber sheeting (a by-product of the petro-chemical industry, apparently) when I was lining a smallish pond (about 6ft X 3ft- see photo) but even at these dimensions I was surprised at the weight of the sheet which, if you’re thinking of lining a large pond or lake, will have to be taken into account i.e. a willing and able-bodied team of helpers.

Initially I was a bit sceptical in that I thought the liner would be too obvious but once the pond was full of water the Butyl wasn’t noticeable at all which was great.

To calculate how much liner you’ll need, make a note of the dimensions of your excavation; length and width, then add to each of these the depth of the hole, multiplied by 2, plus an extra foot (30 cms.) both ways with which to anchor the perimeter edges (either buried in the surrounding soil or under stones, slabs or whatever).

It’s important that you ensure there are no sharp objects such as flint stone or tree roots in the hole as these will puncture the liner and I would advise fitting an under-lay, either purchased with the Butyl or old carpet, ensuring that there are no carpet tacks lurking about, obviously. A layer of sand can also be used to the same effect.

Most text books at the time said to stretch the liner flat out and to let the weight of the water enable the liner to take the shape of the hole but I opted to fit the sheet into the hole first so that I could tuck and fold it as necessary (yes, cosmetic surgery came to my mind as well), a task that would have been impossible once the pond was full of water.

The edging stones should be mortared into place to give the whole construction some permanence and rigidity but bear in mind that any fresh mortar mixture will have to be treated with a neutraliser to eliminate the lime content in the cement before stocking the pond if you’re thinking in terms of fish. This treatment also helps to “age” the fresh cement quickly as it allows algae to grow on it although too much algae can be a problem in ponds but that’s a subject for another day!

And, assuming you have been, thanks for reading…