I'm planning to build a few concrete block garden beds, probably three
blocks high, ten blocks long at the max, on a concrete floor.
What are the growing mediums better suited to this?
Is it a good idea to waterporoof/seal the inner surfaces?
Do you have to use mortar for a wall three bricks high?
I built mine TWO blocks high, on carefully leveled soil. No mortar.
It is just the right height to sit on the edge when I weed it. And it
has not fallen apart, after five years. Gravity and friction hold the
blocks in place.
Might pay to drill holes in the concrete as you will need to have drainage,
as you will end up with dead plants with too much water at root level. Is it
going to be a garden bed or a veggie patch, you should not need mortar as
others have done the same with no problems.
you will need something to lock the blocks together so guessing mortar
will be the go, the base blocks you could mortar to the cement but not
between the block so there is some outlet for water to drain through.
you could create a drain zone under your medium by using rubble or
crushed rock material a layer of 4omm then a layer of 20mm and them
something like cement mix gravel on the top of that and cover with a
double layer of old fly screen or shade cloth to help preven the
medium from clogging this area up. maybe the drainage area could be
app' 1/4 to1/3 the height of a block in depth, assume you mean bessar
blocks or the like?
creat a medium using all sorts of organic material but basically i
would suggest the main ingredient be mushroom compost decomposed or
fresh from the farm no matter try to get hold of any other decomposed
organic material to add in.
'it works for me it could work for you,'
Good day Peter. I'm assuming that your speaking of cinder block? If so,
then yes, you will need to cement them together. If you haven't purchased
bloch yet, I would strongly recommend `allen block. There are many
different makers of this block and it maybe called something else where
your at. These blocks can be found at most big box stores and rock yards.
The advantages to this kind of block is that they lock (kind of) into
place and require no cement. If you want to change the beds, take the
blocks apart and rebuild it again. These blocks also have spaces, cracks
if you will, between the blocks that will allow water to drain. These
blocks come in tons of different styles and I'm sure you could find
something that pleases you. And lastly, they can be rather cheap.
Around here I fill the planters with pea-gravel three inches or so and
fill the rest of the bed with a product called "three way mix". This is a
third mushroom compost, a third skagit river silt and top soil. I just
love this stuff.
or concrete blocks, turning them upwards with the holes facing up, and
securing with rebar to prevent movement. A cinder block wall three high
would take a 4 foot rebar to drive thru the whole way. I have edged my
front beds with cinder blocks until I can afford enough of those
interlocking cement blocks (that come in about six colors and three sizes,
the smallest being 8 inches, the largest being 16 inches wide at the back,
and the mid range one being about 12 inches.)
They do interlock, but if I were you I'd secure them with a little liquid
nails dabbed in the center to stick them. The glue will hold and prevent
any seperation. We do this at Lowes when we set up a display with the
locking blocks built onto cement so that the fork lifts and clumsy loaders
and what not won't knock them all to pieces if they bump them. When we
break them down in the winter, we drop them on their edges to cause the
impact to loosen the grip of the liquid nail and release the cement. The
locking block doesn't chip but the impact is forceful enough to get the
liquid nail to release. And that's just because gravity works in our favor.
We've broken a few, but you'd not break them apart.
The cinder blocks are about $1.23 each or for the largest one, $1.64.
Turned upwards and secured with a driven rebar, you can fill the holes as
well as the inside of the bed you're making and if you're stacking on
cement, you can use the pea rock as drainage as the other men have
suggested. I am using both types of enclosures including landscape timbers
which cover 8 foot lengths and as high as I want, but timbers eventually
rot, no matter if they're treated or not. If I ever use a straight timber,
I'll go to the composite material that last's for 75 years if I want
straight edges and high walls. It's called Everlast and is a bit more than
timbers but heck, it'll outlast me.............and probably the house and
surrounding area! <g>
check the box stores for discontinued patterns on the interlocking blocks.
And see if Depot would sell you slightly chipped blocks. Lowes won't, as
they get 100% credit for them and all their concrete garden stuff like
stepping stones, edgers and the like. They'd rather toss them and get credit
than sell them at reduced prices for people like me who wouldn't mind a few
chips or dings. But discontinued patterns or colors are better. I know I
picked up the red and black ones for 40% off and last year we discontinued a
style that was reminescent of old stone walls in a soft yellow that didn't
go over big. We sold those eventually for 50% off and some gentleman bought
three pallets of them and cleaned us out. He saved a bundle by doing that,
but I can't afford to do stuff like that. I have to do it in batches or
small area's until I get the look I like.
I do like the retaining blocks that lock because they also offer a sitting
spot (or place to put pots) if you go for the 12 inch or 16 inch ones. Just
remember that both the locking blocks that are cement and the bricko or
cinder blocks leech a bit of ph and adjust your soils accordingly. I've lost
a few things planted into the holes that didn't like the "taste" of the ph
and soil once I filled the holes. I think it's more alkeline (? someone set
me straight on this, as I'm not sure if it would be acidic or alkeline) . I
think you'll like either one. I like them both. The cinder blocks for the
ability to secure with a rebar, and the locking blocks for their neat
appearance and more ability to curve (they're fun to fill with soil and
provide pockets for plants to cascade eventually over)
hope this helps a bit more.
Good idea to face the holes up. Cinder blocks that I have left outside
with the holes horizontally have generally collected paper wasp nests.
It forms a nice sheltered environment for them. The wasps don't bother
anyone unless you go to move the blocks during the summer. The wasps
disappear when the weather gets cold and don't re-use the nests next year.
Alkaline, in general. Wet cement has a pH of about 12.5, though can be as
high as 14 -- the same pH as lye oven cleaner, and can cause
caustic burns on long unprotected exposure.
Although some have suggested mortar, cement, etc ,between blocks, I have
grown vegetables for 4 years with very rough sawn old concrete squares just
shoved together and then filled with soil. A little soil leaches out between
the blocks, but I just put small rocks in between to minimize that. In 4
years, I'll bet I have lost no more than a quart of soil out of the entire
10X6 bed, with twice a week overhead irrigation. Every spring I did in 3 of
4 large bags of composted manure and topsoil to replenish the soil, which
tends to compact over time. If it seems a little dense, I might also add
some potting soil. Of course the look is quite rustic, as you can imagine -
it's not a part of the garden for showing off flowers......lol
I would also be concerned about the soil going very alkaline with this much
concrete surrounding it. Sealing would help of course but if any acid loving
crops go bad on you this is why.
Lots of compost in the soil and periodic pH checks would be a good idea.
if you have to or just want to put this raised bed on a concete base,
you could place several lengths of the pipes used for septic systems or
french drains which are full of holes and wrap them in construction
cloth to keep soil from filtering into them and have them come out
from under the little wall you will build so the bed can drain. Like
,space a bottom block so the pipe can peak out and allow the water to
drain out. Also to hold te soil in the bed if no morter is used (I
would not use any morter) you can line the bed with builders
construction costuction paper. I did this on y terraces and it works
I bought some so-called top soil then ammended it heavily with leaves
and various soils from the local supplers and composted cow pooh.
I had a retaining wall leaning back slighty on/into a sloped embankment
going from 1 cement block (8x8x16") to 6 high with only gravity (their
weight ) holding them and no problem for 20 years and still counting.
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