improving drainage on London clay soil

[sacbina]

have removed old turf prior to laying new lawn. have forked over area, removed debris, not yet added the topsoil.
anything I can add to improve drainage to heavy clay soil?
thank you

[MaudantWit]

Does your garden slope? We added a sump (basically a ditch filled with gravel, turfed on top) at the lower end of our lawn, to improve drainage.

[sacbina]

no slope, and grass area is not big, only 6m x 5m
wondered whether adding sand would help?

[Ferguson]

Yes, you can probably add SOME sand, and also organic matter - well rotted manure, or similar commercial products if you can't get natural manure.

And I guess, the deeper you dig it the better, but don't bring 'sour' clay up from too far down.

I stressed 'some' sand, because the garden we inherited 35 years ago, the lawn seemed to be laid on nearly ALL sand. The result has been that in very dry summers the grass suffers greatly.

[aircooled]

There's something called Clay Breaker which is gypsum in a granular form. Have never used it as I've never had a garden with bad clay but it might be worth a try.

[funnyperson]

Leaf mould, compost, rotted manure, will all help: if you usually spread a layer 2-4 inches twice a year, once in early spring and once in late autumn, (technical term=mulch) and also dig in in some whenever you plant anything, your soil will improve.

The RHS advises against adding sand etc: see here
www.rhs.org.uk/advice/profile?PID=620#section-3