Pond build 05

Pond construction

Ron's pond 5. Laying the concrete base

In view of the amount of concrete required, a batch of ready-mixed concrete was delivered to the site. In all, 5m3 was used for the base and when compared to the cost and effort of mixing such a large amount by hand, turned out to be excellent value. The other important factor is the consistency of the mix which guarantees a uniform strength across the base. The cost from a large national company worked out at £80 for delivery plus around £60 per m3 making larger amounts more cost effective. A Semi-Dry mix was specified which ensured that the base could be walked on to create the contours without sinking in too far! The base is 8” deep at the bottom drains and 10” at the edges where the wall will be constructed. TIP. Getting the edge of the base level makes the subsequent wall building much easier, this is achieved by driving in wooden pegs around the pond perimeter to use as a guide when levelling the concrete. The pegs are removed before the concrete goes off.

	The airlines have been threaded along the 1” pressure pipe. The pipe used is ordinary reinforced ½” hose which will not kink or crush inside the pipe.
TIP. If using large diameter airline, do not leave threading the line until the very end as it is not as easy as it might seem, particularly on long runs with knuckle bends. It is best to feed the pipe at an early stage and as you attach the pipework thread the airline along it as you go.

At this stage the concrete has hardened and the photographs show the initial benching and a general shot of the pond layout. Each bottom drain sits in its own saucer shaped depression which ensures debris will move towards each drain. When the walls have been completed, further benching will be carried out. At this point, two courses of blocks have been laid. The blocks are laid to make a 4” wall thickness which will receive a 4” backfill of concrete at a later stage. Laying the blocks on the 4” edge is only possible due to the very stable ground conditions and backfill. If there is any doubt about the solidity of the ground the blocks should be laid on the 9” edge or alternatively hollow blocks should be used. You will see that at this stage the top edges of the bottom drains are still standing around ½” proud of the concrete base. The final concrete rendering will bring them to level. If a liner was being fitted, the concrete would finish flush with the top of the drain.
	Click on any image for a larger image
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This website started with a booklet which I made up originally for the help of those members of the BKKS - South Wales Section who were intending to start building a koi pond, and as the website has expanded more information and articles from other people have been included. This is for general guidance only, and we do not take any responsibility for problems that might occur by following these ideas. It is important that you check out everything in your area, and check on local laws and rules that may apply.

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