Tarpaulin as waterproof

on for the size

I did the same thing using wood plank with no liner, coated the wood with 50/50 paraffin & new engine oil, and afer many years there was still no sign of rot. So whatever you do I can recommend that wood treatment.

NT

Black damp membrane. Under a tenner at screwfix and you'll have lots spare.

Is it to keep the water in or protect the boards? Most alledged tarpaulins these days are woven and will just about stop rain.

How did you stop it leaking? The OP is making a hydroponics pond not just filling it with damp soil. Anyway I wouldn't eat toms that were growing in contact with paraffin and engine oil.

egion for the size

soil's meant to leak :)

Yup, and water or dampness will get between membrane and frame whatever he does. So it makes sense to maximise the timber life expectancy.

The roots arent in contact with it, and the plants dont absorb it. Plants absorb salts.

NT

Probably my very poor way of putting it, but this will be a box full of wet gravel with ordinary pots of soil sitting on top. So a sort of self watering system. The membrane/tarp/pond liner is to keep wet gravel and wood separate. The box will be made of OSB so can imagine if it gets wet it will flake into pieces.

Shot of neighbours system, basic OSB box lined with (in this case) pond liner ) bit of strapping around the top to hold the liner then lots of gravel with water in. You can just see a pot with soil and a tom plant in. Box is on a couple of blocks of wood so it isn't in contact with the cement of her greenhouse floor.

You can get waterproof OSB IIRC.

Never knew that, but the OSB is ordered now, and as it is getting the main cuts before delivery can't very well turn around and send it back.

Thanks all shall investigate the 'waterproof membrane' route.

You could try bubblewrap. Insulation keeps the soil cooler in summer so that less water evaporates off the surface. Don't know how scientifically sound that idea is, but it seems to work for me.

I used to grow toms with the 2 pot method i.e. the top one has the bottom cut out and sits on the lower one, which is filled with gravel or sand. Feed the top, water the bottom kind of thing.

Its called ring culture if anyone wants to look it up.

That is basically the method I am trying out. Only instead of each pot being on another pot, shall have a trough of wet gravel that all the pots will stand on.

I was surprised that the roots went so far down into the lower pot, so removing the base from the top one made that easier. In the end I wasn't convinced they tasted any better than those from the supermarket, so I grew runner beans in builders buckets instead.

When I say "I" I really mean my youngest son (requires lots of attention special school all that) will be doing the actual gardening I am just doing the DIY. I know it is no cheaper than getting veg from the supermarket but he wants to do this and, heh I'm only his dad (so what him and his mum want...).

Quite right too :-)