I am laying about 3 metres square of concrete in my garden (extending
the existing concrete patio).
I was thinking of using the ready mixed concrete bags you can buy.
however i noticed the exiitng concrete has some very large stone
gravel in it. Is it better for me to buy the mix separately? and what
size gravel should I use?
Also do I need a bed or can I lay the concrete straight onto the
I would say if you are concerned about getting the optimal concrete
mix, you should order it pre mixed. You will have to pay for a small
load, but you will save a ton of work. Otherwise, if it's just a
patio and not the front lawn of the White House or something, you
could use pre mixed bags. Your mix won't be as consistent, but it
will be good enough. Don't know what you mean by "large stones".
Typically, concrete for such applications has "3/4- aggregate--that is
a portion of the aggregate contains rock that are 3/4" or less.
Sacrete will also have aggregate, so it should be fine. I wouldn't
recommend mixing your own. It's a ton of work, you will have to come
up with aggregate, and your mix will be even more inconsistent than
Whether you need to lay a "bed" depends on local conditions. If you
have well drained sandy soil it isn't necessary. If you have clay
soil and live where the ground freezes, then you definitely need a
layer of sand.
You may want to re-examine your plan. You said the area was 3 meters
on a side - roughly 100 square feet. Figure 4" thick slab - that's
about 33 cubic feet. If you use 80 pound bags of concrete mix, you'll
need 33/.6, or about 55 bags. Price the bags, the rental cost and
put _some_ value on your time (include fetching and returning the
mixer in your time calcs). Even with a short load of concrete I'd be
shocked if the bags weren't a lot more money. They're definitely a
lot more work.
The way you should go:
The way you're thinking of going:
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