No-dig garden on old building site

Just came across this site- excellent!
so, i knocked down an old building leaving a sandy square about 3m x 3m.
unfortunately, there is some old building material, for example, concrete bits, wood and maybe a small bit of asbestos that are too hard to find from asbestos sheeting (but not much, if any) still mixed into the sand.

I have covered this with black plastic.

Would this still be suitable for a no-dig garden? That is, start on top of the black plastic?

thanks for any comments. Adrian

Comments for No-dig garden on old building site

Click here to add your own comments

Apr 10, 2012
New No Dig Garden over Rubbish NEW
by: Kiwi George

Hi Adrian. Yes, you can build a No Dig garden over anything even concrete and black plastic but I have found that contact with Mother Earth will give you better drainage and the worms will move up to keep your soil in good condition. If you must place your bed over the plastic, put a good drainage layer first then build you No Dig bed on top. While you could build it on the ground as is, be aware that the lime in the concrete and maybe some of the asbestos may have undesirable elements in it which could affect your plants. Otherwise, go for it as No Dig organic gardening is a lifelong learning curve and is fun all the way.

Apr 10, 2012
drainage for No-dig garden on old building site NEW
by: adrian

Thanks, Kiwi George!

i may rethink theplan, anyway, and just put a flower/native plant garden in this spot- no major problem then with the concerete/asbestos, etc...

I will then place the no-dig garden in another , grassy spot.

but, if i were to continue down the no-dig path in this old building's area perhaps you would clarify your comment on drainage?

Do you mean, perhaps, leave a gap between the plastic and the bottom of the garden bed (i.e. raise the base of the garden bed off the ground) to allow drainage out of the bottom of the garden? for instance, a wooden slat base with weed mat covering this base to keep the no-dig material in?

thanks for your time,

Apr 11, 2012
Making a garden on old building site NEW
by: ~ Megan

I believe George probably means it would be wise to make your first layer a drainage layer – using materials such as small rocks or gravel, or heavy sticks etc or something that will absorb water so that your raised bed doesn't fill up with water before it has time to drain out the gaps (don't forget to make gaps or put drainage pipes, at the bottom of the sides would be okay).

If you make holes in your plastic layer, it would seem to defeat the purpose of blocking out any unwanted rubbish from the old building site. Have a read of this:

Plastic is best avoided if you want visiting beneficial worms and bugs. If you think there really is next to nothing dreadful in the ground, then go ahead and make your raised bed no dig garden without the plastic layer. Even if the roots go into the old ground eventually, they are not likely to bring up contaminated material. Just don't go digging things over! It's the micro fine fibres of asbestos that you need to avoid, so wear a mask and keep the surrounding surface area damp to stop breathing anything bad in. Even lead paint flakes can't get into plants, they can only cling on to them.

Best to get a soil analysis if in doubt. Give your local council or government a call, or some universities do tests, as well as of course commercial firms.

Apr 12, 2012
No-dig garden on old building site NEW
by: adrian

Hi Megan,

thanks for your reply, as well.

i am going to look into the soil analysis as you mention- it is not too expensive and in the long run not a bad idea.

i think i can probably remove a top layer, which may improve things- certainly all of the gross product (large bits and pieces, etc.).

thanks for the pointer on drainage.


Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to Garden materials, soil, compost and mulch.

Garden Gift Hub is one of the most thoughtful and interesting places on the web to find original and useful gardening and nature inspired products.

Contact | Home