Building a large square pond

grantcstewart

Hi,

Long before our house was complete and lawn seeded we had a square hole dug out with the intention of one day making an ornamental pond.

Now we are in the planning but I see Alan Titchmarsh makes a concrete base in his design. I was rather hoping to just breeze block and facing bricks the sqaure then place underlay and liner.

Approx size 7x5m, depth between 60cm and 90cm.

Can I avoid the concrete base requirement?

Thanks.

G

Perki

You don't need a concrete base for a pond.

K67

 we just levelled the soil, removed stones, added a layer of sand and  underlay and liner.
The only thing I worried about was the straight sides if the water froze but can't remember why now but we lined the sides with polystyrene before we added the liner.

hogweed

That is a fair size of pond. For an amateur it is easier to lay a liner than a concrete pond. Alan with all the labour, money and expertise at his disposal took the more aesthetically pleasing route. 
Sorry, just reread your post again and you said base - that depends on the soil structure I would have thought. If it is a fairly light sandy soil then I suppose a concrete base would prevent movement? I have never heard before of a concrete base under a liner......

NewBoy2

Set the dimensions
Take a lump hammer and smack all of the exposed soil to get rid of sharp stones.
Add some old bed spreads or curtains to roughly line the interior.
Add a  tough membrane and possibly an underlay....Olay !!
Order pond marginal plants and plants that suit different levels.
Fill with water and a week later the wild life will move in !
Eat a pasty and drink some wine.

K67

@NewBoy2
Great advice until pasty with wine! Surely it should be beer or a craft ale.🤔

KT53

I'm assuming they are still available, but it will be far easier to install a made to measure butyl liner than just using butyl sheet as there will be a huge amount to try to effectively fold out of the way at the corners. 

K67

They do bespoke pond liners price in butyl for your size about £700.

Pete.8

K67 said:

 The only thing I worried about was the straight sides if the water froze but can't remember why now but we lined the sides with polystyrene before we added the liner.

Water expands as it freezes and I have heard of cracked ponds after thick ice has formed on the surface of ponds with flat sides. There's no space for the water to expand horizontally, so the expanding water cracks the sides of the pond - much like a frozen pipe.
Of course if you live somewhere relatively mild that may not be a problem

Sounds like a great project
Good luck!