Shallow soil over tarmac...

[occasionalposter]

I have an unusual gardening dilemma - part of my garden is consists of about 8 inches of soil over an unbroken (as far as I can tell) stretch of tarmac. It is currently grass, which tends to be very brown in the summer.

My dilemma is what to do about it - the grass isn't very satisfactory and I'm not a big fan of it at the best of times. I had thought about putting down a gravel garden, but all the plants seem to need a 'well drained' soil and I'm not sure that the tarmac does drain well, although since it used to be a road I suppose it does have a camber on it to allow run off.....
anyway, any advice or suggestions gratefully received!

Could you give the gravel plan a go on a small area to try it out? It can't be much worse than brown grass.

Do you want plants with height or are you after ground cover?

Ideally a mixture of both - but I could get some height with grasses, which ought to be fairly shallow rooted. There is a strip of garden next to the fence with deeper soil as the developer has cut through the road to put in a curb that retains the garden soil (hence the 8 inches of soil!) so I could put a shrub or two in there!
Do you think I should put membrane under the gravel as well?

This is a big no-no. If somehow you could get the tarmac broken up (by pickaxe or hydraulic drill in an ideal world) it would make a great base for a gravel garden.
Please don't spend any money on plants in the present conditions though, you may as well flush it down the loo.

Oh dear, that is what I was afrid of - do you think that nothing will grow at all? Is it because of the drainage or because tarmac is inherently at problem?

The drainage is your problem. As you have seen the grass, which will try to grow anywhere, dies back every year. If you bought ornamental grasses, they would do the same thing.

The tarmac isn't a very nice base to start from but if you can break it up and incorporate some decent compost and topsoil, there's no reason why you couldn't start growing some tough plants there. Think Buddleia, Kerria japonica, Cotoneaster, which will try to grow in cracks in the paving anyway.
I'd do that initially then get some other softer plants in if the pioneers succeed.

Btw, I'm a RHS qualified landscaper so have a little bit of experience

Thank you for the advice - I have been dithering about this for some time, it appears I was right to be concerned!
Do you have any advce as to what I could do wihtout spending money? Breaking up the tarmac would be very difficult - it really is a road and I'm sure it is a minimum of 5 inches thick (at least the chunks of tarmac I dug up in the back garden with the yellow lines painted on them were).
Any ideas graetfully received!

another route would be to gravel it and use lots of pots?

I could do the pots thing, but we have an imminent hosepipe ban here, so might be a bit tricky to keep them watered.

The only other option I can think of is raised beds built on the current soil. That would probably give my plants some drainage, although I would have to water them. How deep (high?) do you think they would need to be?

PS Sorry for the dodgy spelling - I can spell but I can't type!

Good idea. I'd go for knee height but experts here probably know better.

Raised beds about knee height (usually two railway sleepers) with lots of broken hardcore/crocks/mixed stone in the bottom for your drainage might work.

Otherwise get a strapping lad with a pickaxe who wants to earn £60 cash for a day's worth of brute force to break up the road underneath?

Actually, although I 'm not sure I know any 'strapping' lads - DD may have some friends who would like to earn a few quid......

Hired a concrete breaker for the day a month ago. Was just under £80. Would make light work of a road, though it's a really dull job to have to do.

Oooh, sounds interesting! I can do dull and the thought occurs that DD's friends might need feeding as well as paying (could be uneconomical given what teenage lads can eat....)
Where did you hire it from ?

Ebley Plant, Eagle Plant and HSS toolhire all do great big toys tools for destroying things with. Google them for your nearest.
And let us know how it goes!