My allotment has a severe drainage problem so I'm building raised beds,
which I hope will help. As well as manure and compost, I want to add
something else to improve drainage. It's clay soil. What should I use --
pea gravel or sand (builders sand?) or something else?

Thanks.

Ade wrote:
My allotment has a severe drainage problem so I'm building raised beds,
which I hope will help. As well as manure and compost, I want to add
something else to improve drainage. It's clay soil. What should I use --
pea gravel or sand (builders sand?) or something else?

How deep do you need your beds to be?! You've added manure and compost
- is this around 30cm depth?! If so, I think that the manure will
improve your soil and if you keep adding it on top years after years
you'll end up with fantastic beds. I wouldn't start using gravel or
sand because you don't know what you'll grow say in 2 years time. It
depends on your rotation plan but also what you want to grow. I had a
corner on my lotty so compact with clay I thought nothing would ever
grow. I've added manure for 2 years - then potatoes and now perhaps 2
spit down it is clay but there's enough manured top soil to grow my
leeks this year, garlic and kale walking sticks )

Ade wrote:
My allotment has a severe drainage problem so I'm building raised beds,
which I hope will help. As well as manure and compost, I want to add
something else to improve drainage. It's clay soil. What should I use --
pea gravel or sand (builders sand?) or something else?

Topsoil.

http://www.onlineturf.com/partners/onlinesoil/index.asp

Maybe cheaper from builders merchants or similar locally
to you. Cheaper per unit in quantity. Everything depends
on what you (or other allotment holders if they're at all
interested) want to spend.