I am planning to build raised vegetable garden beds. One option is to
use manufactured hollow concrete blocks. The beds will be 1.4 m (4 ft)
by 10 m (30 ft). the standard blocks are nominally 200mm (8 ") high so
I need two courses high. This will be built on a site that has a gentle
slope, the area for the beds will be levelled beforehand. Drains will
be built to prevent ground water from coursing through the vege garden.
We don't have earthquakes, snow, floods, tornados or hurricanes.

The soil is dark and fertile but rather heavy with quite a high
proportion of clay. The inside of the beds will be filled with this
soil amended with compost etc. The blocks come in nominal 100mm (4")
150mm (6") and 200mm (8") widths. The price of the blocks is roughly
proportionate to the width.

My question is what kind of construction do I need to make these beds
stable while not spending time and money over-engineering them? I don't
mind the odd small crack here or there but the walls must not fall over.

As I see it the walls would be stretcher bond but could be:
1) laid dry
2) mortared
3) reinforced
4) mortared and reinforced

Obviously the cheapest will be 100mm blocks laid dry but I wonder if
they will be stable. Mortared and reinforced 200mm will be very strong
but also rather expensive. What is by best compromise that is stable
under these conditions for the least cost?

David

"David Hare-Scott" wrote:

I am planning to build raised vegetable garden beds. One option is to
use manufactured hollow concrete blocks.
I need two courses high.

My question is what kind of construction do I need to make these beds
stable while not spending time and money over-engineering them?

As I see it the walls would be stretcher bond but could be:

3) reinforced

Lay up the courses and pound 3/8" rebar "hairpins" or "candy
canes" through the holes into the dirt every couple of feet.
Pass the ends of the rebar over the intersection of two blocks,
through the holes and into the dirt.

This will make it stable enough to keep the vegetables from
escaping, but if you want to enlarge or remove, you just yank out
the rebar and unstack the blocks.


Tsu

--
To doubt everything or to believe everything
are two equally convenient solutions; both
dispense with the necessity of reflection.
- Jules Henri Poincaré

"Tsu Dho Nimh" wrote in message
...
"David Hare-Scott" wrote:

I am planning to build raised vegetable garden beds. One option is
to
use manufactured hollow concrete blocks.
I need two courses high.

My question is what kind of construction do I need to make these beds
stable while not spending time and money over-engineering them?

As I see it the walls would be stretcher bond but could be:

3) reinforced

Lay up the courses and pound 3/8" rebar "hairpins" or "candy
canes" through the holes into the dirt every couple of feet.
Pass the ends of the rebar over the intersection of two blocks,
through the holes and into the dirt.

This will make it stable enough to keep the vegetables from
escaping, but if you want to enlarge or remove, you just yank out
the rebar and unstack the blocks.


Tsu


So you are suggesting the 100mm (4") blocks, laid dry and tied
vertically with rebar, is that it?

The common pattern produced here has two holes through the blocks
vertically so I can stagger the courses and still get the rebar through.
This sounds simple and effective to me. How long will the rebar last
out in the open before it rusts so much it is useless?

David

I don't see any problem with you rplans so long as there are no invasive
trees or shrubs within 200'. That minimal height should cause no instability
problems. Reinforcing rod would help stabilize stress points, as at
walkways. Also barring any locally invasive weeds or grasses, this should
work ok. Otherwise you might need a cement barrier below ground for 12-18"
to keep out the invaders. Nearby trees, look for another place.
"David Hare-Scott" wrote in message
u...
I am planning to build raised vegetable garden beds. One option is to
use manufactured hollow concrete blocks. The beds will be 1.4 m (4 ft)
by 10 m (30 ft). the standard blocks are nominally 200mm (8 ") high so
I need two courses high. This will be built on a site that has a gentle
slope, the area for the beds will be levelled beforehand. Drains will
be built to prevent ground water from coursing through the vege garden.
We don't have earthquakes, snow, floods, tornados or hurricanes.

The soil is dark and fertile but rather heavy with quite a high
proportion of clay. The inside of the beds will be filled with this
soil amended with compost etc. The blocks come in nominal 100mm (4")
150mm (6") and 200mm (8") widths. The price of the blocks is roughly
proportionate to the width.

My question is what kind of construction do I need to make these beds
stable while not spending time and money over-engineering them? I don't
mind the odd small crack here or there but the walls must not fall over.

As I see it the walls would be stretcher bond but could be:
1) laid dry
2) mortared
3) reinforced
4) mortared and reinforced

Obviously the cheapest will be 100mm blocks laid dry but I wonder if
they will be stable. Mortared and reinforced 200mm will be very strong
but also rather expensive. What is by best compromise that is stable
under these conditions for the least cost?

David

Dry stack, pound in 5/8 rebar down flush or lower then top, fill all holes
w/ dirt. To make more stable, mix in 10% cement / the dirt. But just soil
is good for two courses.

Howdy folks,
On the production side of the garden bed, run some weed cloth down
the inside of the block to prevent some of your weeds like Bermuda
grass that propagate underground from taking up residence under the
blocks or in the cavities or else you'll be fighting them forever. On
the outside of the walls holding a garden bed, run some weed cloth
flat, and cover with a heavy mulch to keep the weeds away from the
wall, and save on trimmer string.
This is more of a gardening tip than a construction tip but you do
want to do it when you build the wall so it is a consideration during
construction.

Steve Coyle
www.austingardencenter.com

I made raised beds with cinder blocks a couple of years ago. I
originally put them in sans mortar with the rebar as mentioned. They
kept falling over whenever I worked the beds. I then put them in with
mortar on a thin footing. I'm not very adept at this sort of thing, but
the beds are still up. I filled the holes in the blocks with some gravel
to within an inch or so of the top and topped it off with the left over
mortar and cement. I garden in a cold climate and I was worried about
frost heaves, but no problems so far. Only drawback is that I can't put
my supports next to the bed walls like I could with the dried laid walls
or wood walls. A small inconvience when compared with the savings of
time on repairing the beds each year.

David Hare-Scott wrote:

I am planning to build raised vegetable garden beds. One option is to
use manufactured hollow concrete blocks. The beds will be 1.4 m (4 ft)
by 10 m (30 ft). the standard blocks are nominally 200mm (8 ") high so
I need two courses high. This will be built on a site that has a gentle
slope, the area for the beds will be levelled beforehand. Drains will
be built to prevent ground water from coursing through the vege garden.
We don't have earthquakes, snow, floods, tornados or hurricanes.

The soil is dark and fertile but rather heavy with quite a high
proportion of clay. The inside of the beds will be filled with this
soil amended with compost etc. The blocks come in nominal 100mm (4")
150mm (6") and 200mm (8") widths. The price of the blocks is roughly
proportionate to the width.

My question is what kind of construction do I need to make these beds
stable while not spending time and money over-engineering them? I don't
mind the odd small crack here or there but the walls must not fall over.

As I see it the walls would be stretcher bond but could be:
1) laid dry
2) mortared
3) reinforced
4) mortared and reinforced

Obviously the cheapest will be 100mm blocks laid dry but I wonder if
they will be stable. Mortared and reinforced 200mm will be very strong
but also rather expensive. What is by best compromise that is stable
under these conditions for the least cost?

David







--
To reply, if 'nospam' is present in address, just remove it.

On Wed, 16 Jul 2003 17:53:13 -0600, AF
wrote:

I made raised beds with cinder blocks a couple of years ago. I
originally put them in sans mortar with the rebar as mentioned. They
kept falling over whenever I worked the beds.

I made a raised bed at least five years ago with two courses of
blocks. I merely leveled the ground they would rest on, as well as I
could.

I used no mortar, rebar, or anything else.

I've had no trouble with them.

vince norris