Question
Hi Sean, the back yard of my recently purchased house has a brick circular
patterned patio just as you go out into the garden which then leads onto a
big patch of concrete. It looks pretty thick and takes up the whole of the rear
of the (quite small) yard. (about 18ft x 15ft I think) but I haven't measured it
yet) and I think the man before us had a large workshop/construction built
over it as the surrounding walls of the garden are all blackened. I don't have
very much money so I can't dig out the concrete...so what I wanted to do was
put a raised area with some steps going up to a bit of lawn and maybe a
paved corner. I live in London, England so rain and drainage is a BIG issue! Cn
I just drill some holes down through the concrete and then build a wall, fill
with gravel or something and then earth and turf? Help! I have no clue. was
hoping for the raised bit to be 2 or 3 shallow steps up with a red brick low
wall containing it...thank you for any input, Amie..ps. would it help if I sent a
photo?

Answer
Amie
London, wow...you are really out of my realm of plant knowledge but as for hardscape I think I can answer this one.

First, I think if you did the research you would quickly find that the cost of building walls, adding steps and then drilling the concrete and filling over it by adding soil and plants would far outweigh the cost of removing the concrete and planting. I may be wrong but here in my locale this would definitely be the case.

However, the short answer to your question is yes you could drill the concrete so it would drain. But you would need lots of holes and they would need to be large holes of a min of 2" diameter in order to avoid being clogged in the future. And at each hole you would need gravel. You would need one of these holes ever 2 feet in either direction to efficiently drain the area. Even if you did all this, there is still a good chance the soil near the top of the concrete would remain wet for long periods of time and set up soil conditions that would not be the best for healthy plant growth.

In addition to the cost to do this, it would always be difficult to get anything but small plants and grass to grow well in a shallow soil bed.

Despite all this, I think you would be surprised how easily you can remove the concrete. Assuming it is typical 4" thick and has no steel in it you should be able to do it yourself or hire a handy man/laborer for a day or two. All you need to do is rent a jack hammer from your local tool rental and pick up a large sledge hammer. 18x15 should take one person a day or less to break up into small pieces (no more than 12x12x4) and then another half day at the most to haul it off. I'm 37 and in reasonable shape. I have done this much concrete in and hauled it off in one day by myself (but I did get some blisters) This also requires a large waste container be delivered to your residence. In my are the removal would cost about $1.50 sf. American dollars.

So that is the best I can tell you. Good Luck and don't hurt your back what ever you do.
Sean J Murphy, LA,ISA, LEED AP
Please check out my blogs and articles on landscape topics like this on my websites.
http://www.seanjmurphy.com
http://amenityarchitects.com