Filling in a concrete fish pond - I would like to put a patio over it

[jenny]

I am a DIY enthusiast and keen gardener but this is my first attempt at landscape gardening! I have a 6ft x 6ft concrete fish pond (approximately 2 ft deep) with a small wall around it surrounded by patio. The fish have long gone and it has been completely drained for some time now. What I would like to do is fill in the pond, knock down the wall and have a patio over the pond to meet with the existing patio. I have been advised to break up the bottom of the pond to allow for drainage. My questions are, Do I need to break up the bottom of the pond?, What do I fill it in with ? and How do I get it level with the existing patio?

[alan ditchfield]

If the pond has been drained for a while and has not filled up with the rain i would not bother breaking the base, i would knock down the walls put them in the base fill the remainder with crusher to a level suitable when compacted to accept the laying course and the paving to bring it level with the existing patio.

[jenny]

I was informed that if I didn't break up the base water could possibly get in at a later date . As I am a novice at this could you advise me, How deep do I fill it with hardcore? (I have lots of bricks and large stones to throw in) What is crusher and to what height level do I fill it?

[steve r]

Jenny, as Alan says if the pond hasn't filled with water then there is no reason to break up the bottom provided you take the sides out then any water can get out.
Although the area will only take light loads and normally you wouldn't need much of a subase, you are reinstating the fish pond and unless done properly you may find that it will be liable to settlement over time.
You should fill the pond in layers of no more than 150mm thick and compact them as you go.
Have a look at this page patios and see how you get on

[jenny]

Thankyou Alan and Steve for your advice but me no speak builder!What am I layering with and what do I use to compact it with? Sorry to seem dumb (1st attempt and all) I have tried trawling the site but can't seem to find anything on filling in a deep area . I was intending the space to be used for a picnic bench or table and chairs is this o.k Any advise greatly appreciated (please provide idot speak) Thanks!

[Tony McC]

You fill the 'hole' by building-up layers of a suitable crushed aggregate. It's probably easiest for you to get a crusher run or Type 1 material from your local Builders' Merchant, so I won't befuddle you with details of SF2's and Type 4s, etc.

You place and level the crushed stone in layers that are not more than 200mm deep, and you thoroughly compact each layer before placing, levelling and compacting the next layer.

To compact, you use a vibrating plate compactor, a roller, a rammer or similar.

All this info is actually given on the sub-bases page and if you'd followed the link kindly provided by SteveR, that would have led you to the information on how to build-up levels and how to consolidate.

Does that make it clearer?

[jenny]

Thankyou so much for spelling it out for me Tony, and yes it is clearer. I found the sub-bases link very helpful.